Yield potential of peanuts at Mackay - What are the key barriers to obtaining it?

Take home messages

Australian peanut producers are commonly only achieving 50-70% of the genetic yield potential of commercial peanut varieties. Growers now have the significant advantage of being able to tap into many years of research and development work and the collective experience of the industry's agronomists and farmers to capitalise on best management practices (BMP) that produce profitable and sustainable crops of high yield and kernel quality.

Coastal growers in cane areas should employ all of the recognised BMP practices to reduce their production risks optimise yield and profitability and maximise the long-term benefits to the cane production system. Peanuts offer an excellent and profitable rotation crop for cane.

What is the potential yield of peanuts?

Experimentation crop modelling and overseas experience indicates a very large yield potential in the range of 8.0 to >11.0 t/ha. Practical field local experience in trials and farmers' fields indicates a very large variation with irrigated yields generally ranging from 3-6 t/ha pay weight. Less than 3.5 to 4.0 t/ha is indicative of a relative failure especially if production costs have been high or returns are low due to price or grades. The industry average in 2001 was approx 3.9 t/ha

Yield gap and BMP

Generally better growers are achieving in the range of 4.5 to 7.0 t/ha with some farmers having reported up to 8.0 t/ha. Frequently yields do not exceed 6.0 t/ha. Failure to align with the essential elements of BMP in peanut production generally results in either failure to achieve target yields or a consistent decline in yields over ensuing years. BMP relates both to the management factors employed in the overall farming system and the specific management techniques applied to peanut crop agronomy and management operations. New peanut growers have an excellent opportunity to implement BMP from start-up because of the collective experience of researchers and agronomists and the valuable practical knowledge of fellow peanut producers.

The GRDC-funded project "Best Management Practices in the Production of High Input Peanuts" conducted by DPI&F has allowed successful and sustainable peanut production methods to be documented and made readily available.

Importantly new production environments such as Mackay and the Burdekin will present new challenges for defining BMP given the specific conditions that apply in each region particularly in relation to optimum planting and harvesting windows. However the essential rules for successful production remain the same across regions. BMP focuses on sustainable yield in a profitable framework involving the whole farming system.

Key barriers?

Primary factors determining peanut yields will vary from region to region and year to year. Growers should embrace the 'rig ht approach' and lean towards treating peanuts more like a horticultural crop than a grain or cane crop. Peanuts are extremely responsive to good intensive management and have specific requirements in terms of the critical timing of field operations.

Get the right advice relating to production requirements from the outset. Engage with professional agronomists and share important experiences and information with local colleagues. Plan ahead for the whole production process in terms of contracting peanut product through to harvest and transport to a processor. Irrigation weed and disease control and harvest management will be very important considerations. Growers need to commit to high cash input costs to maximise yield and reduce risk. Avoid over-committing resources; especially labour inputs and irrigation water. Ensure access to and effective operation of spray and harvesting equipment. Consider using contractors and sharing the cost of machinery purchases to minimise risks and improve production efficiency.

Start with the right soil type for harvesting the crop. Aim to have well-prepared weed-free fields with good internal soil drainage and minimal we spots. Poor drainage can severely impact on yield especially in extended high rainfall periods.

1. Harvest losses as affected by

• Soil type and soil management. Hard-setting and heavy soils are unsuitable.
• Poor late season disease control can reduce pod quality and harvestability
• Harvest management and timely access to harvesting equipment is critical.
• Careful assessment of crop maturity to optimise yield and quality.
• Kernel quality and aflatoxin resulting from delayed threshing and drying.

2. Disease can commonly be the largest yield limitation and include-

• Early leaf spot (Cercospora arachidicola)
• Late leaf spot (Cercosporidium personatum)
• Rust (Puccinia arachidis)
• Net blotch (Didymosphaeria arachidicola )
• White mould (Sclerotium rolfsii)
• Sclerotinia rot (Sclerotinia sclerotiorum and Sclerotinia minor)
• CBR (Cylindrocladium parasiticum)

There are inherent issues of kernel quality and aflatoxin contamination caused by Aspergillus flavus that can be aggravated by poor disease control. Peanut producers have access to an excellent range of proven options that work well if adhered to. These include combining important elements of Integrated Disease Management that will assist overall disease control. Stick to the rules of

• Control of peanut volunteers which harbour disease between crop cycles
• Prevention not cure - fungicides are much more effective if used preventatively
• Thorough and regular disease scouting
• Timely routine and strategic fungicide application in line with label recommendations
• Rotation of chemistry to avoid resistance
• Good spray application technology
• Effective crop rotation. Soil-borne disease is a less an issue in cane farming systems. Rotations minimise incidence of leaf and soil-borne diseases

3. Irrigation management

Irrigators should avoid staving off watering in favour of possible rain to minimise crop stress. Budget total crop water use prior to planting (5-7 ML/ha). Peanuts are very sensitive to water stress despite their toughness as a crop. Minimise water stress during the critical flowering to pod-fill stages. Stress can increase the incidence of disease and ultimately affect kernel quality. Uniformity of water application is a major issue often arising from inadequate equipment or poor system design. Soils most suited to peanuts generally have very low water holding capacity so water use must be carefully monitored. Know the required irrigation intervals to maintain adequate soil water.

4. Plant population and crop uniformity

There is an all too regular occurrence of inadequate and uneven plant population. Target plant populations of approx 100000 to 120000 per ha. Crop uniformity is very important with gaps punching holes in yield! The crop has only limited ability to compensate for gaps. Row spacing can be important at higher plant population and yield levels. Plant into moisture with press wheels and use a precision planter if possible. Good plant populations compete very effectively with weeds.

5. Weed control

Plant into a clean weed-free field. Early weed control in the first 6-8 weeks of growth is crucial. Peanuts have an excellent range of weed control options both pre and post emergent. Avoid inter-row cultivation as this can promote disease. Timeliness is critical - control weeds when they are small to maximise yield and reduce cost. Use pre-plant or pre-emergent weed control options to reduce weed control risks and costs. Avoid late season weed infestations that can severely impact yield and ease of harvesting operations.

6. Nutrition

Use a soil test - P K and micronutrients. Monitor soil pH and use lime if necessary. Gypsum application (cadmium-free) helps to ensure adequate calcium is available during pod-filling. Inoculate seed with care. Excessive cane trash levels will often hinder early crop growth. Incorporate trash well before sowing and consider a starter fertiliser that includes 10-15 kg/ha of nitrogen. Applied fertiliser nitrogen is not otherwise recommended since peanuts are a very good nitrogen fixer. Consult with Peanut Company of Australia regarding avoiding cadmium incidence or the associated pricing penalties.

7. Radiation and heat units

Tropical zones have extended periods of reduced solar radiation. Adequate heat units and solar radiation are essential for crop growth pod-fill and crop maturation. Disease and associated harvest losses are increased by extended overcast conditions. Avoidance is sometimes impossible but can be managed to some extent using suitable production windows. However optimum production windows may not suit the cane rotation. Avoid considering planting windows that are likely to fail in order to accommodate cane production programs. Frost may also be risk in some local areas for winter season production.

Further reading

• DPIF Summer Crop Notes - Latest version available August 2004.
• DPIF website at http//www.dpi.qld.gov.au/fieldcrops/
• Nuts-2-U the DPIF newsletter of the "BMP in High Input Peanut Production" project.

Appendices

APSIM Peanut is a simulated computer crop modelling analysis of peanut growth development and yield. In recent times model simulations have been shown to provide very useful and sometimes very accurate analyses of crop performance parameters. This is especially useful when considering planting options production risks and outcomes and potential crop performance and profitability. It is now being used as both a research tool and as a decision support aid for regional peanut production.

APSIM Peanut uses all of the historical climate data including rainfall temperature radiation and applied irrigation to predict yield outcomes. Actual field trials continue to assist with model verification. Additional work needs to be conducted in the Burdekin and Mackay regions to cater for specific production scenarios and climatic zones which can vary considerably within each region.

How good is the model? The graph below highlights yield outcomes against model predictions in various production locations. Note the close correlation of the model to actual field performance.

Figure 1. Relationship between observed and APSIM simulated peanut pod-yield in different environments

Peanut maturity will vary considerably according to planting window and variety type. The following graph allows growers to estimate what day of the year any variety might mature given a nominated planting date.

For example Florunner planted on January 14th will likely mature in mid-June. Planted on November 9th it will come in around late March. Maturity will be considerably delayed by insufficient heat units between June and August-September. Peanuts prefer to mature under optimal temperature conditions. Conversely extreme heat will slow the crop development down and delay maturity. VB97 is shortest duration variety and Conder is the longest.

Figure 2. Maturity time of different peanut cultivars in different sowings at Mackay

Following is an example of sowing date versus maturity for Florunner peanuts planted sequentially throughout the year using crop simulations.

How to read a box plot. The solid section of each bar represents the results from 70% of simulations. This equates roughly to the majority of results we may observe in the field. The solid line across the bar represents the median figure. The dotted line is the average or mean. The lines projecting from the box plot represent the upper and lower limits of the result over all historical years in which data is available.

For example planting on May 2nd we can expect maturity to fluctuate between approximately 173 and 190 days but in 70% of cases it is likely to range from approximately 177 to 186 days with the median being 183 days.

Figure 3. Box plot of days to maturity of Florunner peanut in sequential sowings at Mackay

Crop yields look extremely attractive with some of the autumn/winter sowing dates. Note the significant jump in potential yield associated with planting from early May to late August for Florunner (figure 4.).

Figure 4. Box plot of the potential pod-yield (kg/ha) of Florunner peanut in sequential sowings at Mackay

Peanuts can be sown throughout a considerable part of the year with potentially reasonable and at times very good yield results. However the harvestability of the crop may vary. Occasional frost in colder areas will curtail or impair crop development. Extended cool conditions that force the crops to grow for over 200 days will cause failure. A major determinant of crop success will be the weather at harvest and this is clearly demonstrated in the following graph. Note the greater variability of yield outcomes with a traditional summer versus the autumn/winter planting window.

Figure 5. Box plot of harvestable pod-yield (kg/ha) of Florunner peanut in sequential sowings at Mackay

The high yield potential and expected advantages of an autumn/winter plant are even more attractive with longer maturity varieties such as Conder.

Figure 6. Box plot of the potential pod-yield (kg/ha) of Conder peanut in sequential sowings at Mackay

However high yield potential is associated with greater variability of actual harvested yield outcomes. Note the huge variations from the following graph and the inherent risks of some planting dates. March April sowing indicates likely crop failure due to cool conditions. September-November sowing dates have a much higher yield variability. Some sowing windows offer considerable yield advantages ie. June.

Figure 7. Box plot of harvestable pod-yield (kg/ha) of Conder peanut in sequential sowings at Mackay

DPIF will eventually be able to generate additional data from regional trials and commercial production fields to fine-tune the usefulness of APSIM Peanut. This will greatly assist with regional growers being able to assess the potential yield and risk of particular sowing dates including measuring crop duration potential water use and optimum varietal choice yield and harvestability.

Varieties displaying this symbol beside them are protected under the Plant Breeders Rights Act 1994.