POTENTIAL USE OF NEAR INFRARED REFLECTANCE (NIR) MONITORING IN SUGARCANE PRECISION AGRICULTURE (PAG)

J.H. Meyer
meyer@sugar.org.za

South African Sugar Association Experiment Station, South Africa.

Precision Agriculture (PAG) or Site Specific Management practices have grown in leaps and bounds in the USA and other countries and has shaped the way for efficient use of resource inputs such as herbicides and fertilizers while maximizing crop production. Modern combine harvesters and tractors come equipped with Global Positioning Systems (GPS), which enables the operator to deduce their position in the field. In the USA, combines with GPS yield monitors have increased from below 1,000 in 1995 to over 15,000 in 1999.

The concept of Precision Farming, also known as "soil or site specific management," "farming by soil," and "farming by the foot," is not new and interest in the potential benefits of PAG gathered momentum in the late eighties. Advances in computers and greater precision in remote sensing capabilities have largely spawned the emerging technology of PAG. These days, combines are highly computerized and continuously measure grain yield during harvest. New developments include the use of NIR technology to continuously monitor the composition of grain with reference to moisture, protein starch and oil content. While all these developments are fast taking place in the grain crop industry, seemingly few developments in the field of continuous yield and quality mapping have taken place for sugarcane.

Until recently in the sugar industry, NIR detectors have been calibrated for manual scanning of soil and leaf samples in the laboratory (Meyer 1983, 1989) and for monitoring cane quality (Meyer 1987, Clark et al 1996, and Berding 1989), while on line NIR systems for cane payment are also now in operation in a number of countries including Brazil and Australia. The advent of small compact diode array and Acoustic Optic Tunable Filters (AOTF), makes NIR a powerful analytical technique, capable of fast, accurate, almost simultaneous quantitative measurement of many components in a complex mixture. It is these new generation NIR units that have been fitted to combine harvesters and other mobile sampling devices.

In this communication, the potential role of NIR in PAG with reference to some of the following stages will be examined:

• Yield and quality monitoring and mapping
• Soil and leaf sampling and analysis
• Remote sensing
• Variable rate applicators

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A SUMMARY OF PRECISION FARMING RESULTS FOR SOUTH FLORID

A Michael Lockhart, Richard Price and Travis Murray
lockhartag@earthlink.net

Lockhart Ag Technologies, USA.

The increase in sugarcane acreage in South Florida during the past ten years has been mostly to the sandier soils that are west of the Everglades Agricultural Area. Aerial infrared photographs of the sugarcane grown in this area have demonstrated a high degree of variability in the photosynthetic activity of the crop. There are multiple reasons for reduced plant vigor in some areas of these fields. For example, statistical analysis of over 800 sand land samples collected in central Hendry County has shown a high correlation among soil pH, Si, Ca, Mg, organic matter, K and P (Muchovej and Lockhart, 1999). During the past four years, thousands of acres of sandy soils in south Florida have been sampled using precision farming techniques. Based on the results, it has been determined that some Flatwoods soils of central Hendry County require a sampling intensity of one sample per acre to sufficiently identify the variability of soil pH and several plant nutrients. Soil pH values have been shown to routinely vary from 3.8 to as high as 8.0 within the same field. Laboratory experiments have been conducted which show that mixing equal volumes of soil from high and low pH areas can result in unpredictable values for the composite sample. For example, a soil sample with a pH after drying of 4.54 was mixed with a soil sample from the same field that had a pH of 7.80. The pH of a mixture of equal volumes of these two soils was determined to be 7.60 after they had been dried overnight. Liming rates for the acidic areas of the fields now far exceed the maximum two tons per acre lime recommendation from the University of Florida. Lime calibration studies are presently underway on both the west and east sides of Lake Okeechobee. In one experiment, the soil pH in the treatment receiving ten tons of dolomite per acre has increased from 4.0 to only 6.3 one year after application. Site-specific treatment using soil amendments and fertilizer was a logistical nightmare until the introduction of the Differential Global Positioning System (DGPS). Multiple sites within selected fields have been soil sampled and aerially photographed on an annual basis to verify the ability of the multiple rate application approach to improve the uniformity of soil pH, plant nutrients and overall crop vigor.

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THE USE OF DIGITAL INFRARED IMAGERY IN VARIABLE RATE APPLICATION OF FERTILIZER IN SUGARCANE

Christopher Niven
images@millerlegg.com

GeoImaging, LLC, USA.

The traditional approach to crop production throughout the world is to base the rate of application for materials such as lime and fertilizer on laboratory analysis of composite soil samples. Recent unpublished research (Lockhart, 2000) has demonstrated that data based on composite or mixed soil samples may not provide the best information about soil conditions, especially when soil characteristics in the field vary in frequency, extent and distribution. Areas of poor crop vigor (so-called "poor spots") are often seen throughout sugarcane fields having sandy and transitional (muck to sand) soils. However, these same fields are normally treated with single rate applications of fertilizers and soil amendments based on composite soil samples.

Two historic hurdles in sugarcane production on sandy and transitional soils were the definition of where the "poor spots" were located and how to treat these areas in a cumulative manner while still providing a different and appropriate technique to optimize production in areas of good vegetative vigor. Traditional techniques and equipment did not allow the development of treatments that considered the actual variability of soil conditions and vegetative health. Developing treatments based on the relative vegetative health or soil condition of a field as a whole consistently resulted in non-uniform crop yields that often exhibited stark contrast between areas of good and poor production.

Using digital infrared imagery to identify areas of low, medium and high vegetative health can geographically define where "poor spots" exist. Once the range of crop health is defined over the entire field using remote sensing and statistical analysis, geo-referenced digital maps of the field can be produced. The digital map is the key to managing areas within individual fields using specific and different treatments. Additional data such as soil and leaf tissue samples and grower experience and judgment can be incorporated into the application maps of various products. Each individual field can be fertilized and/or treated with other materials based on its own unique characteristics.

The results of this project demonstrate the ability to define and treat areas of sugarcane fields based on the health of the vegetation. The areas defined using imagery were compared to VR application maps developed from one acre GPS-based soil samples. Results indicate that soil condition and vegetative health vary in an extent and frequency that cannot always be detected using a one-acre grid. The digital infrared imagery "samples" the field conditions using a one-meter grid.

For two fields near Clewiston, Florida, the variable rate / digital infrared approach reduced the expected decrease in tonnage from plant cane to first stubble cane commonly associated with traditional fertilization techniques. Each field received three variable rate applications of fertilizer. The revenue generated provided a positive return on the investment in the use of digital infrared imagery, GPS-based soil samples and variable rate application of lime, calcium silicate slag, and fertilizer.

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AGRONOMIC EVALUATION OF RELEASED VARIETIES IN SOUTH AFRICA

Kerry Redshaw
redshawk@sugar.org.za

South African Sugar Association Experiment Station, South Africa.

The Released Variety Trial (RVT) Programme at the South African Sugar Experiment Station (SASEX) at Mount Edgecombe was established in 1966 and has been an extremely successful programme that is fairly unique to South Africa. The South African Sugar Industry is spread over a wide range of soil and agro climatic zones. There are also many different management styles and levels of the growers themselves that range from small, medium to large-scale growers. The correct choice of variety in terms of its specific adaptability, economic viability, age of cane at harvest and overall management cost can make a large difference in the overall profit a grower will incur at the end of a season. The RVT programme is designed to test released varieties at a number of different localities around the Sugar Industry, which provides the basis for advising the best choice of varieties.

A systems approach has recently been introduced to the Agronomy Department at SASEX and this has refocused the objective not only of the RVT programme, but also of the department as a whole. Data collected from variety trials is inserted into a database along with growth analysis, weed control and water management trials. Prior to the systems approach, information collected from a variety trial and hence the variety recommendations, were very specific to a particular season. Data from weather stations is now readily available to be included in the analysis of trial data. One of the aims of the systems approach is to redirect the existing resources into increasing the number of measurements taken from each trial to ensure that the performance of varieties can be explained more effectively throughout a particular season. However, this will be at the expense of the number of trials located throughout the industry. The positioning of trials will need to be managed more carefully to ensure that the most important agro climatic zones and soil types are represented. Growth analysis trials will identify and quantify variety traits of importance that will be incorporated into the sugarcane crop model. The systems approach aims to collate this variety data together with climate and soils data to assist in making recommendations and in predicting crop performance through the use of weather forecasting.

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CHARACTERISTICS OF SUGARCANE RHIZOSPHERE UNDER FLOODING

D.R. Morris and P.Y.P. Tai
mailto:dmorris@usda.ars.gov

USDA-ARS Sugarcane Field Station, USA.

Organic soil in the Everglades Agricultural Area have been reported to be subsiding at 1.3 cm/yr. Oxidation of organic matter by aerobic soil microorganisms is one of the leading factors of soil loss. In the process of soil oxidation, nutrients such as N and P are released. One way to reduce subsidence is to flood the soils. An experiment was conducted at Canal Point, Florida to investigate the rhizosphere microbial populations and chemistry as affected by different sugarcane varieties under flooded conditions. Five sugarcane varieties (US 87-1006, US 96-1083, US 96-1106, US 96-1112, and CP 65-357) were grown under three water-table levels (0, 15, and 30 cm from the top of the bucket) in 38 L plastic buckets containing a 1:2 mixture of sand and organic soil. Sugarcane was grown outside for 10 months (Apr. 1999 to Feb. 2000) with water-table treatments imposed after a 4-month growth period. At harvest, senescing leaves were discarded and stalks were cut at the soil surface level. Soil samples were taken in the 0-15 (A) and 15-30 (B)-cm depths and microbial counts (bacteria, actinomycetes, and fungi) and chemistry (water extractable pH, NH4-N, NO3/NO2-N, total organic carbon (TOC), and PO4-P) were analyzed. Stalk dry matter, total sugar yield, % sugar in dry matter, and number of stalks were not reduced when water was maintained at 15-cm depth compared to the non-flooded treatment. Correlation between plant yield and rhizosphere parameters showed there was a negative correlation with TOC levels in the upper soil. It appears that plants that lose more soluble carbohydrates around their root systems have lower sugar yields. Large differences in rhizosphere microbial populations were not obtained. However, populations were generally low and averaged 1.2 X 105, 4.1 X 103, and 2.6 X 102 for bacteria, actinomycetes and fungi, respectively, in the A and B horizons. The low number of microorganisms may have been due to the relatively high soil pH encountered in these soils, which averaged 7.9 in the A and B surfaces. There was a significant correlation between bacterial populations in the A horizon and TOC (average 32 ppm) in both the A and B horizons. It appears TOC has a positive effect on bacterial populations in the rhizosphere. Actinomycetes were not influenced by TOC, but were found to decline with high water table treatment in the A soil layer. Fungi were not influenced by either water table or cultivar. Available N (NH4-N, NO3/NO2-N) and P (PO4-P) in the rhizosphere were not affected by cultivar or water table. Plants and microbes probably utilized all the available N and P necessary for growth until there were uniform low levels. Amounts in the rhizosphere averaged 0.23, 1.09, and 0.32 ppm for NH4-N, NO3/NO2-N, and PO4-P, respectively, in the A and B layers. Our data indicated the TOC in the rhizosphere is an important variable related to both crop yield and bacterial populations. Future research will be required to quantify those relationships.

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RESEARCH INTO SOIL AND WATER LOSSES FROM SUGARCANE FIELDS IN SOUTH AFRICA

G. W. Maher
maher@sugar.org.za

South African Sugar Association Experiment Station, South Africa.

A research project was initiated in the late 1970's by the South African Sugar Association Experiment Station to study factors that contribute to soil and water losses from sugarcane fields. A modeling approach, based on the Universal Soil Loss Equation (USLE), was used to determine values for the factors under local conditions. The objective of the project was to produce recommendations for protective practices. The research methods using small catchments, runoff plots and a rainfall simulator are described. Results from the research project were used to construct a nomograph to determine panel widths in sugarcane fields in South Africa. The construction of the nomograph to compute the panel widths is described.

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LONGTERM EFFECTS OF TRASH RETENTION ON CANE YIELD AND SOIL FERTILITY USING RESULTS FROM A 60 YEAR OLD TRIAL AT MOUNT EDGECOMBE

Jan H. Meyer¹, R. van Antwerpen¹, M.H. Graham² and R.J. Haynes²
mailto:meyer@sugar.org.za
antwerpen@sugar.org.za

1. South African Sugar Association Experiment Station, South Africa.
2. School of Applied Environmental Sciences, University of Natal, South Africa.

The long-term effects of green cane harvesting with trash retention, compared with burning, on sucrose yield and soil fertility was assessed using data from a trash management trial established on a vertisol at Mount Edgecombe (BT1) just over 60 years ago. Average results obtained for 35 crops from 5 crop cycles indicated a positive response to trash retention in 24 crops. In general, positive responses to trash retention were associated with crops harvested at 15 months and older and particularly where the rainfall was below the long-term mean. Whilst the benefits of moisture conservation from trash retention have long been recognized, there is now also evidence that trashing can result in a substantial improvement in soil fertility. The BT1 results showed a significant increase in soil organic matter content in the surface 10 cm of soil from trash retention that resulted in a higher total and potentially mineralizable soil N. The size of the microbial biomass and its respiratory rate, dehydrogenase activity and arginine ammonification rate were also increased by trash retention. Exchangeable K concentrations also increased markedly under trash retention reflecting the large amounts of K that are returned in trash. As expected, both exchangeable and non-exchangeable soil K concentrations as well as plant available P levels were higher in fertilized than non-fertilized treatments. Trash retention also tended to result in a decline in pH due to the greater amount of N cycling in the system. It was concluded that recommended N and K fertilizer rates could be lowered under green cane harvesting and that regular lime applications are important when acidifying nitrogenous fertilizers are being used routinely.

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USE OF PRINCIPAL COMPONENTS ANALYSIS IN THE STUDY OF FACTORS ASSOCIATED WITH SUGARCANE RESPONSE TO NITROGEN FERTILIZER UNDER SUBTROPICAL CONDITIONS OF TUCUMAN - ARGENTINA

Federico Perez Zamora, Mariana Rufino, Jorge Scandaliaris, Eduardo Romero
mailto:agronomia@eeaoc.org.ar

Estacion Experimental Agro Industrial Obispo Colombres, Argentina.

The province of Tucuman with its 200,000 hectares represents the most important sugarcane producing areas of Argentina that is heterogeneous in soil factors as a result of soil origin, relief and annual rainfall variation.

Results from soil analysis of a profiles net spread in all the sugarcane area indicate soil organic matter contents that range between 0.91 to 3.14 % in the 0-30 cm layer of the profile, with soil textures varying from sandy loam to clay loam. Also, the drainage conditions are variable existing two clearly different zones: one which has well to excessive drained soils at the foot of the mountain and the central plain which has moderate to restricted drainage. In the latter, conditions of water logging occur at intermittent periods in January and February coinciding with the main growing season.

Since 1994 to 1998, the Obispo Colombres Experiment Station carried out 58 trials to determine the productivity responses of the ratoon crops to N fertilizer applications assessing rates from 25 to 300 kg N/ha.

The data provided by each experiment was analyzed using Cate and Nelson discontinuous Model. Afterwards, a reduced centered matrix was built up taking into account the following:

• The response parameters of the Cate and Nelson Model (Relative Yield, Optimum Nitrogen Rate, Consume Index and Stable Maximum Yield).
• The variables that indicate the soil Nitrogen supply (Soil Organic matter content, potential to mineralize N from soil organic matter, Total Nitrogen).
• The variable that quantifies the crop nutritional status (N% TVD leaf).

With all the data above mentioned, a Principal Components Analysis was made.

The Yield increments were determined to be inversely related to soil N supply in each of its parameters and to the nutritional status of the control plot, shown by the leaf N concentration. This was defined by the application of the Cosines Rule.

The optimum rate was not directly associated with N supply and could only be related by means of its combination with the Consume Index (ratio between Optimum rate and Stable Maximum Yield).

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THE GREEN CANE HARVESTING SYSTEM - AN AUSTRALIAN PERSPECTIVE

Graham Kingston and Chris Norris
gkingston@bses.org.au
cnorris@bses.org.au

Bureau of Sugar Experiment Stations, Australia.

Green cane harvesting has been adopted for 70% of the cane harvest in Queensland, but adoption ranges from 4 to 100%. Adoption in the New South Wales industry is less than 5%. There is low adoption in a tropical irrigation area because of concern that trash residues reduce efficiency of furrow irrigation. Low adoption in NSW is more a function of concern about reduced productivity with conservation of resides under cool and wet conditions. Mechanical cane harvesting capacity in both areas of low adoption is heavily committed to harvest of burnt cane. Reduced harvest rate in green cane is therefore seen as an economic issue in need for greater capital investment without commensurate increase in throughput.

Commercial strategies for managing trash are reviewed, along with potential impacts of these options on crop nutrition.

Results of a three year study of trash management techniques in the New South Wales industry show retention of a full trash blanket is uneconomic for winter harvested cane. Raking trash reduces yield loss and is economic in some situations. Retention of a trash blanket has a higher marginal return than the conventional two year burnt cane system for spring and summer harvest, except for heavy clay soil in a higher rainfall zone. Crop physiology studies show yield effects are not explained fully by prevailing temperatures.

Mechanical cane harvesters were originally designed to harvest burnt cane. Current green cane harvesting capacity is largely the result of modifications to power input and cleaning systems. These modifications have not addressed need for improved feeding of green cane into the harvester and have increased loss of cane and juice in the machine. The paper highlights results of recent Australian research in these areas.

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LONG-TERM EXPERIMENTS ON GREEN CANE TRASH MANAGEMENT

Jorge Torres and Fernando Villegas
mailto:jtorres@cenicana.org

Cenicana, Colombia.

The Colombia sugar industry and the government have signed an agreement to eliminate pre-harvest burning of cane fields before year 2005. Cane farmers are well aware of the need to adjust cultural practices to maintain the economic viability of cane production. After green cane harvesting of commercial varieties, the amount of fresh residues left behind can vary between 50 to 150 t/ha, making it necessary to find short-term alternatives for green cane management under heavy trash conditions.

When it happens to rain after the harvest, it is common to observe excess moisture at the soil surface creating stool rooting and therefore poor germination of commercial fields. In Colombia, year round harvesting is practiced which may have a negative impact on cane production due impaired stool germination and stunted stalk growth due to the presence of residues. Several field trials have been conducted with different varieties and on different soils. A long term experiment is being conducted with V 71-51 variety on a Mollisol to identify the best trash management treatment which includes: 1- A trash blanket evenly distributed over the stool and inter-space (0x0); 2- Trash raked into a windrow on every inter-row (1x1); 3- Trash raked into a windrow placed on every other inter-row (1x1); 4-Two inter-rows with trash windrow followed by two interspaces without trash; 5- A blanket of trash, chopped by a forage harvester.

Right after green harvesting of the plant cane crop, the proposed trash management treatments were imposed in a commercial plantation. Cane yields of first and second ratoon crops were similar in all trash management treatments including burnt cane. Third ratoon cane yields of 0x0, 0x1 and 1x1 trash treatments, where there is no chance to conduct cultural practices, were 40% lower than other treatments. This fact emphasizes the need to conduct cultivation practices to incorporate fertilizers and restore soil physical properties; otherwise, a significant cane yield decline is expected. To verify this hypothesis, non-mechanized treatment plots were replaced by other trash management treatments; as a result, overall cane-yield of fourth and fifth ratoon crops were similar or better than the reference check treatment of burnt cane before harvest.

Under the Colombian conditions, it is essential to conduct green cane trash management treatments that allow for mechanized cultural practices; otherwise, cane production is affected.

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NUTRIENT AND DRY MATTER RETURNS IN CROP RESIDUES FROM BURNT AND UNBURNT SUGARCANE SYSTEMS

Ross D.J. Mitchell1, Fiona A. Robertson1, Graham A. Kingston1 and Peter Larsen2
mailto:gkingston@bses.org.au

1. Bureau of Sugar Experiment Stations, Australia.

2. GRO, Australia.

Retention of crop residues, instead of burning them, may allow greater organic matter and nutrient retention in the soil. This would have implications for fertilizer requirements and water use. The recovery of nutrients (nitrogen, N; calcium, Ca; magnesium, Mg; phosphorus, P; potassium, K; and, sulfur, S) and dry matter (DM) in burnt and unburnt residues (non-millable above ground biomass) were quantified in a series of eight field experiments in central and northern Queensland. The experiments were intended to indicate nutrient and DM retention in the immediate area of the fire only, with no allowance being made for re-deposition of airborne material.

The quantity of DM and nutrients (except K) in sugarcane residues (tops, trash and total residue) were linearly related to mechanically harvested sugarcane yield (fresh weight, FW) (r2+0.50-0.88). The nutrient and DM recovered after burning the standing crop was 5-32% of initial inputs. The quantity of nutrients in unburnt residues that would have been lost by burning (the unburnt-burnt differential), also tended to increase linearly as crop yield increased. The effect of these nutrient and DM returns on soil carbon (C) and nutrients was assessed in six short-medium term (1-33 years) experiments. The additional nutrients returned after one year of residue retention was insufficient to increase available soil K or total C and N. Six to eight years of residue retention was sufficient to increase the total C by ca 30-50% in the surface soil (0-5cm), and the total N by 9-60%. Although microbial biomass was increased by comparable proportions, the net N mineralization potential was not affected by residue retention.

Potassium was rapidly leached from cane residues by simulated rainfall and was assumed as equivalent to inorganic fertilizer K additions. The plant available soil K reached equilibrium with differential K fertilizer inputs (0-196 kg K/ha/year) after ca. 15-20 years. Beyond this equilibrium, the quantity of K in the cane residues was positively related to historical K application. The linear relationship between K input and crop off take, indicates that 25-30 kg K/ha/year would become available for sugarcane uptake from extra nutrient retained in trash of a typically yielding crop of sugarcane.

The data presented in this paper indicate that the additional quantities of nutrients and DM retained when sugarcane residues are not burnt, can, for some nutrients, be conveniently estimated from a universally available data set (crop yield). Although total soil N content has been increased by 6-8 years of trash retention, N availability was apparently unaffected. The greater K retention may more immediately effect fertilizer requirements and reductions of 25-30 kg/ha may be possible.

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USE OF FIRE RETARDANTS IN SUGAR CANE FIELDS: PRELIMINARY RESULTS

S. Seeruttun, C. Barbe, M. Mangar and J. Deville
sseerut@msiri.intnet.mu
mailto:jdeville@msiri.intnet.mu

Mauritius Sugar Industry Research Institute, Mauritius.

Accidental fires to standing cane and green cane trash blankets cause significant economic losses and crop management problems every year; more than 2500 ha (3% of area under cane) were burnt in 1998. Cane fires have also discouraged some farmers from adopting green cane trash blanketing. The efficacy of a fire retardant, Magma®, has been evaluated on trash blankets; preliminary tests have shown that the product needs to be applied or coated on all sides of trash to be effective. Spraying the product on the upper surface of a trash layer or blanket with a knapsack sprayer, irrespective of nozzle types, and increasing both rates of product from 10 to 100 g/m2 and volume of water to almost a drenching situation did not improve efficacy. Promising results have been obtained by the use of air-assisted spraying; the progressing fire stopped when reaching a 2 m band treated with a mist-blower delivering about 1.2 L/minute and 25 g/m2 of product. The optimum amount of product, minimum width of treated band and its efficacy on standing cane is being determined.

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VERTICAL MULCHING - A TILLAGE TECHNIQUE TO IMPROVE CANE YIELDS ON MARGINAL SOILS

R van Antwerpen and J.H. Meyer
antwerpen@sugar.org.za
mailto:meyer@sugar.org.za

South African Sugar Association Experiment Station, South Africa.

Low water intake rates due either to natural surface crusting or smearing effects from compaction is recognized as a severe problem in limiting water use efficiency in both rain-fed and irrigated cane areas of the world. The performance of cane established under vertical mulching (VM) tillage was compared with that grown under normal cultivation in two rain-fed and two irrigated trials. Materials used as ameliorants with VM included topsoil, river sand, gypsum and filtercake. VM with filtercake was the most effective treatment resulting in responses of 1.2 ton sucrose per hectare per annum on average. The residual effect of VM with filtercake in the longest running trial lasted for 11 crops prior to the termination of the trial. A major benefit of VM with filtercake was an improvement in the terminal intake rate from an average of 36 mm/hr in the control treatment to 108 mm/hr for VM with filtercake. Other soil properties that benefited from this treatment included water distribution, water infiltration, effective rooting depth and root distribution. Although VM with filtercake seemed to be costly, it was shown that if the nutrient value of filtercake is ignored (which is considerable) that the breakeven point is less than two years.

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INNOVATIVE MANAGEMENT TECHNIQUES TO MINIMIZE AGROCHEMICAL EXPORT AND MAXIMIZE PROFITABILITY FROM AUSTRALIAN CANELANDS

John Reghenzani, B.W. Simpson and J.D. Armour
jreghenzani@bses.org.au

Bureau of Sugar Experiment Stations, Australia.

The Australian sugar industry has recognized the need for greater research, development and extension of improved environmental management practices. The results of this program are currently being extended to the industry by the Cooperative Research Center for Sustainable Sugar Production (CRC Sugar) and its partners through a series of Environmental Short Courses. This paper outlines advice currently being presented to the Australian industry on innovative management techniques to minimize agrochemical loss from cane fields.

Management techniques that minimize agrochemical export from cane lands have benefits for both growers and the environment. Farmers benefit from reduced costs, improved agrochemical use efficiency and enhanced profitability. Environmental and wider community benefits include less degradation of natural resources such as surface and underground water as well as improved sustainability and life style in the longer term. It is necessary to take the wider and long-term view of improved management options. Management to reduce losses by one pathway can increase losses to others. A coordinated plan to reduce nutrient loss should be accompanied by reduced inputs.

Improved efficiency of plant uptake of all nutrients would result from the management options for nitrogen (N) and phosphorus (P) suggested here. While there is a limited range of pesticides in use and increased green-cane harvesting with trash retention have reduced requirements for herbicides, farmers are strongly encouraged to take a responsible approach to pesticide application. This will occur with more information on pesticides behavior in the environment and increased publicity for improved techniques.

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INJURY TO SUGARCANE IN THE HERBERT RIVER REGION OF AUSTRALIA FOLLOWING THE APPLICATION OF CALCIUM AMMONIUM NITRATE

John Reghenzani
mailto:jreghenzani@bses.org.au

Bureau of Sugar Experiment Stations, Australia.

Due to favorable pricing of calcium ammonium nitrate (CAN) fertilizer, a number of farmers in the Herbert River Region of Australia used this nitrogenous fertilizer to side dress plant cane in 1999. The cane looked healthy until about six weeks after application, when heavy rainfall resulted in water logging. Within three days of the onset of anaerobic conditions, necrotic lesions appeared on foliage and the cane began to die. Preliminary tests in the field did not indicate water logging or fertilizer burn as basic causes of the problem. Analysis of the product did not indicate contamination by herbicides.

Although less severe, foliar lesions were reproduced where CAN was applied in trials conducted at the better-drained regional sugar experiment station. Onset of these symptoms was within three days of treatment application. Soil extracts did not indicate the presence of detectable levels of nitrite. These trials indicated that urea applied at similar rates of nitrogen did not have any adverse effect. Symptom development was very dependent on the degree of water logging. A mixture of ammonium nitrate and lime in similar proportions to that present in CAN also result in lesion development. Application of iron sulfate to the foliage in addition to CAN reduced the percentage of foliar lesions. Another nitrogenous fertilizer ammonium sulfate nitrogen (ASN) produced lesions, but to a lesser extent.

While only a few field sites exhibited severe symptoms and sugarcane death, this problem was of concern, as the basic cause remains unknown. A preliminary literature search and communication with field staff has failed to provide evidence of documented cases of crop death following the application of CAN or ASN in Australia or elsewhere. While this may indicate that the problem is rare, the total loss of the crop in the cases documented in this paper is of concern, particularly if the conditions that caused death were to occur over a larger area. As a result of this problem in the Herbert region, the use of CAN is not recommended in fields of plant cane that may be subject to water logging.

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RESPONSE OF SUGARCANE WILT TO ZINC AND SULPHUR AND ITS IMPACT ON YIELD AND JUICE QUALITY

K. Lal, Aneg Singh, Atul Singh and S.B. Singh
upcrs@lw1.vsnl.net.in

U.P. Council of Sugarcane Research, India.

A field experiment, conducted at the Sugarcane Research Institute, Shahjahanpur, located at 27.53º N latitude and 79.54º E longitude under the subtropical conditions of India, revealed that a basal application of Zn at 25.0 kg ha-1 and S at 50.0 kg ha-1 or their foliar application (0.5% each) alone or in combination to CoS 92254 sugarcane reduced the wilt incidence and increased the number of shoots, NMC and cane yield significantly. Sucrose percent in juice was also enhanced markedly with Zn and S treatments. The addition of S and Zn at S1Zn1 (50.0 kg ha-1 S + 25.0 kg ha-1 Zn as a basal spray) and S2Zn2 (0.5% S + 0.5% Zn as a foliar spray) levels decreased the disease intensity resulting in the improvement of crop productivity. In general, both the disease severity and crop losses decreased with the increasing levels of S and Zn in the soil.

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CEMENT AS SILICON SOURCE FOR SUGARCANE

Gaspar Korndorfer¹ and M. Benedini²
mailto:ghk@triang.com.br

1. Universidade Federal de Uberlandia, Instituto de Ciencias Agrarias, Brazil.

2. Usina Nova Uniao, Ribeirao Preto, Brazil.

In Brazil, silicon is an element little considered in the plant nutrition research, but it is known that this element can help and improve plant protection against plagues and diseases. This work had the objective to study the effect of cement as a silicon source and its effects on plagues (borer), disease management (rust) and sugarcane yield and quality. For such research, three sugarcane cultivars (SP71-6163; SP79-1011 and RB72454) and five silicon rates coming from cement (0, 500, 1000, 2000 and 4000 kg ha-1 of Si) were used. The randomized block design was selected in order to distribute the treatments in a field, and the statistical model was accomplished into the factorial design. The Si application increased cane productivity. Soluble Si, exchangeable-Ca and pH also increased where cement was applied. Silicon did not affect borer attack incidence. The cultivar yield decreased in the following order: RB72454>SP79-1011>SP71-6163.

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TRANSFORMING THEORETICAL FARMING KNOWLEDGE TO PRACTICAL APPLICATIONS

Norman Rozeff
mailto:rcgcrgr@rgvsugar.com

Rio Grande Valley Sugar Growers, USA.

From the ivory tower to the field, the dissemination of knowledge requires an evolutionary process whereby theoretical ideas are modified and communicated in language and ways understandable to the end user. An example that shows a three-generation transformation from theoretical to practical is presented. The example deals with the theme development on the subject "Limitations to Sugarcane Production."

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IMPLICATIONS OF GENETICALLY TRANSFORMED CORN, COTTON, AND SOYBEANS FOR HERBICIDE RESISTANCE FOR SUGARCANE IN LOUISIANA

Edward P. Richard, Jr.
erichard@nola.srrc.usda.gov

USDA-ARS Sugarcane Research Unit, USA.

At least 50% of the corn, cotton, and soybean planted in the U.S. are cultivars that have been genetically transformed to be resistant to postemergence applications of glyphosate. This technology offers the grower the flexibility of using an effective, broad spectrum, environmentally friendly herbicide to control troublesome annual and perennial weeds without fear of crop injury and only when weeds are present at economically impacting levels. In the southern U.S. where perennial weeds like bermudagrass (Cynodon dactylon) and johnsongrass (Sorghum halepense) are a problem, the use of this technology is especially attractive. The adaption of this technology has also had an indirect impact on the U.S. cane sugar industry and Louisiana's industry in particular.

Approximately 20 percent of the sugarcane area in Louisiana is fallowed each year in anticipation for replanting in late summer. Often, these fallowed fields are subjected to frequent diskings and multiple applications of relatively high rates of glyphosate to control rhizomatous bermudagrass and johnsongrass which cannot be selectively eliminated within the crop. In some of the fallowed fields, sugarcane growers opt to plant multiple drills of glyphosate-resistant corn or soybeans on established sugarcane beds. When possible, the crops are harvested and the income used to offset expenditures for land preparation and seeding. By planting multiple drills on established sugarcane beds, growers take advantage of the foliar cover of the crop to suppress weed development. Ultimately, this reduces the need for higher rates and multiple applications of glyphosate and results in additional savings.

As the area planted to glyphosate-resistant crops has increased in the U.S., sales of pre-emergence herbicides for use in these crops have decreased. To offset the reductions in sales, companies have been forced to turn their attention to the sale of herbicides in crops such as sugarcane, which have not been transformed for herbicide resistance. To increase their presence in these crops, manufacturers have offered price-reduction incentives or rebates to make their products more economically acceptable to growers. In Louisiana, the cost of the herbicides pendimethalin and metribuzin has been reduced by 15 to 25 percent through rebate offers.

The acceptability of the herbicide-resistant technology in the seeded crops has also spurred manufacturer interest in the development of soil-active herbicides for non-transformed crops like sugarcane. Several of these herbicides, azafenidin by DuPont and clomazone and sulfentrazone by FMC, are projected to have full registrations by 2001. In addition, manufacturers have also turned their attention towards the development of herbicides that can be applied in mixture with glyphosate to improve some of glyphosate's shortcomings such as its lack of residualness and its poor control of morningglories (Ipomoea spp.) and the nutsedges (Cyperus spp.). Currently, four of these herbicides are being evaluated in Louisiana for the control of morningglory and nutsedge, as well as other weeds, when applied alone in sugarcane or in mixture with glyphosate in fallowed fields.

If public acceptance of genetically modified crops increases, the sugarcane industry of Louisiana will certainly benefit from the planting of glyphosate-resistant sugarcane, particularly in fields having a history of being severely infested with perennial grass weeds. Nevertheless, the Louisiana cane sugar industry has benefited indirectly from the development of this technology in seeded crops through the reduction in costs for weed control and the introduction of new products.

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SUGARCANE AND EVERGLADES RESTORATION

Barry Glaz and Marcel Aillery
bglaz@saa.ars.usda.gov

USDA-ARS Sugarcane Field Station, USA.

Restoration of the Everglades and other linked ecosystems in South Florida is one of the most far-reaching ecological restoration programs ever undertaken. The purpose of this discussion will be to explore strategies by which the agricultural sciences can serve sugarcane growers in the Everglades Agricultural Area (EAA) to enable them to participate as partners in the restoration process. Key ecological issues in the Everglades are phosphorus enrichment, changes in timings and quantities of water delivery, and changes in habitat. Human issues linked to these ecological issues include economic viability of sugarcane both with and without changes that favor the natural Everglades conservation of the organic soils of the EAA. Multi- disciplinary research is discussed to help resolve these ecological and human issues. (1) Agronomic and genetic research to incrementally raise the water table in commercial sugarcane fields without reducing profits. (2) Microbiological research to determine durations and depths of water tables necessary to control oxidation of organic soils and further research to determine residual effects of previous floods or high water tables. (3) Soil and plant nutrition research to link to the agronomic and microbiological work to determine their effects on phosphorus and nitrogen release and sugarcane phosphorus and nitrogen nutrition. (4) Linkages with hydrologic modelers of public agencies so they can include basin-wide incremental changes occurring in the EAA into their Everglades models as long-term Everglades restoration proceeds through adaptive management.

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ENVIRONMENTAL MANAGEMENT GUIDELINES FOR SUGARCANE IN SOUTH AFRICA

G.W. Maher
maher@sugar.org.za

South African Association Extension Office, South Africa.

Environmental management guidelines have been developed for the South African sugarcane grower. This follows an internationally recognized environmental management system. The contents of these guidelines are outlined. An approach to obligatory environmental audits required by the system is described and includes the make-up of the audit procedure in relation to the guidelines. The procedure for scoring and rating of individual farms is described, as is a reporting system developed to outline an action plan to correct deficiencies.

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PESTICIDE REVIEWS AND IMPLICATIONS FOR THE U.S. SUGARCANE INDUSTRY

Dudley T. Smith¹, Ryan P. Viator¹, and Leonard P. Gianessi²
dt-smith@tamu.edu
sviator@cactr.lsu.edu

1. Texas A&M University, USA.

2. National Center for Food and Agricultural Policy, USA.

The 1996 Food Quality Protection Act mandated new regulatory requirements for the U.S. Environmental Protection Agency (USEPA). Currently labeled and new chemicals are subjected to complex dietary and non-dietary, occupational, and fate/environmental considerations, with less importance placed on the economic benefits of pesticides. Since numerous weed, disease, and insect pests limit sugarcane productivity, the retention of current pesticides and availability of new products are important to sustain profitability. Although sugarcane acreage in the U.S. approaches 1 million acres, commercial firms are not particularly interested in this pesticide market due to high costs of development, geographic diversity in the U.S. industry, and regulatory requirements. Public and private sector research continues to focus on cultural, biological, and other means of non-chemical control of pests, but pesticide development is still essential for the future. While some environmental economic, and social factors appear to limit pesticide development, several research initiatives are continuing on pesticides and integrated pest management for the future.

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ENVIRONMENTAL ASPECTS OF PRE-HARVEST BURNING OF SUGARCANE IN FLORIDA

John W. Dunckelman and Michael R. Bellamy
johndunckelman@sugarcaneleague.org

Florida Sugar Cane League, USA.

The environmental aspects of conducting standing pre-harvest burning of the Florida sugarcane harvest is discussed in relation to monitoring of air quality and avoidance of nuisance effects on residential areas in and around the Everglades Agricultural Area, a large expanse of farmland in Florida to the south of Lake Okeechobee. Current sugarcane production in Florida now stands at approximately 1.95 million short tons of sugar from 455,000 acres. This places Florida as the top sugar producing state of the U.S.A. It also opens the industry to criticism regarding the environmental impact of employed farming practices, including pre-harvest burning for trash reduction prior to harvesting. Sugarcane burning practices are reviewed and air quality monitoring efforts of the industry are discussed. An examination of PM-10 data in relation to sugarcane burning, the National Ambient Air Quality Standards, and factors such as weather patterns is made. The possible impact of new regulations such as the PM-2.5 standard is reviewed from the standpoint of agricultural burning in south Florida, and the industry's future outlook for the continued use of fire in sugarcane agriculture is projected.

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Using Geo-referenced IR Imagery to Define and Treat Areas of Varied Sugar Cane Productivity: Methods and results, South Florida, 1999

Christopher Niven
mailto:images@millerlegg.com

GeoImaging, LLC, USA.

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GREEN CANE TRASH BLANKETING: ACHIEVEMENTS AND LIMITATIONS UNDER MAURITIAN CONDITIONS

S. Seeruttun, C. Barbe, A. Gaungoo and G. McIntyre
mailto:sserutt@msiri.intnet.mu
mailto:guymc@msiri.intnet.mu.

Sugar Research and Development Corporation, Australia.

Green cane trash blanketing (GCTB) was recommended in the sub-humid areas of Mauritius in 1992 following trial results showing increases in cane yield, less labor requirement for trash management in manually harvested fields and a better control of weeds. The adoption of GCTB was boosted with the expansion of mechanical harvest, especially with chopper harvesters. With GCTB, the first pre-emergence herbicide application is avoided and some fields may even reach the next harvest without any herbicide application. This practice has thus contributed to reduce significantly the total amount of herbicides used in sugarcane. GCTB has, however, some limitations in areas with more than 3000 mm of annual rainfall as the resulting high level of soil moisture and decrease in soil temperature lead to a significant decrease in cane yield. As weed control is, also, not necessarily improved by GCTB in these areas, the trash should be raked and lined in the inter-rows. With increasing pressure to reduce cane burning and the extension of chopper harvesters, GCTB is expected to become the main trash management practice in coming years in areas other than those of the super humid zone of Mauritius.

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EFFECT OF PURPLE NUTSEDGE (CYPERUS ROTUNDUS L.) COMPETITION IN FLORIDA SUGARCANE (SACCHARUM spp.)

Matthew J. Duchrow and James M. Shine, Jr.
mduchrow@scgc.org
jmshine@scgc.org

Sugar Cane Growers Cooperative of Florida, USA.

Purple nutsedge (Cyperus rotundus L.) causes yield losses in many agronomic crops. Yield losses associated with purple nutsedge in sugarcane (Saccharum spp.) have not been studied extensively. Partial additive studies were conducted in containers to determine the effect of interference of different initial population densities of purple nutsedge on sugarcane. Five commercial cultivars were evaluated: CP72-2086, CP80-1827, CP80-1743, CP88-1762, and CP89-2143. Purple nutsedge tubers were planted at densities of 50, 100, 150, 200 and 250 tubers/m2. Purple nutsedge densities as low as 50/m2 significantly (?<0.05) reduced sugarcane fresh weight, number of tillers, and primary stalk fresh weight, and primary stalk diameter in the plant cane crop. Total fresh weight reduction at 250 purple nutsedge tubers/m2 ranged from 19% in CP80-1827 to 29% in CP80-1743. Tiller numbers were reduced from 4% in CP80-1827 to 37% in CP80-1743. Losses in primary stalk diameter ranged from 4% in CP80-1743 to14% in CP80-1827 and CP88-1762. Primary stalk fresh weight losses ranged from 16% in CP72-2086 to 36% in CP80-1827.

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