Rotations balancing agronomics & economics

It is important to understand that healthy crop rotations make healthier crops and more productive fields. In mother nature there are no monoculture crops like what we are growing in agriculture.

Seeding the same thing every second year is not a rotation. Planting the same crop, at the same time and spraying the same products encourage pests, diseases, weeds, and fertility problems. Cool winter temperatures slow the breakdown of residues so they remain to perpetuate pest problems. Reducing these pressures leads to healthier plants that may not need to be sprayed with a pesticide.

A crop rotation can increase your yields even if you don’t change anything else. Larger yields and reduced pest pressure may result in higher returns. Planting a variety of crops allows a larger number of pesticides to be used, reducing the chance of resistance becoming a major issue. Planning a rotation allows you to use more agronomic tools to maximize the economic returns. Having a healthy rotation gives you more flexibility versus a back to back rotation such as canola/wheat or lentil/durum.

Any crop rotation should be based on sound principles but remain flexible to allow for variations in the seasonal break, commodity prices and changing circumstances. What happens in one paddock is linked to activities across the farm, such as balancing grazing demands or spreading commodity and financial risk.

It is also important that economic returns from a canola crop are considered for the full term of the cropping rotation and not just on an individual crop basis. Research has shown that the benefits from growing canola can flow on to subsequent crops for two or three years after the initial canola crop. While preparing a simple gross margin on the canola crop will give a guide to the input costs and potential returns, it does not take longer-term benefits into consideration nor does it spread some long-term costs – such as the application of lime/gypsum – over several crops. The benefits of having canola in the rotation include:

• Reduced incidence of diseases such as take-all, crown rot and common root rot in winter cereal crops grown after canola through the removal of their grass weed hosts. Numerous studies have demonstrated an average yield increase of 20 per cent in wheat crops grown after canola compared to wheat grown after wheat. If disease levels are high, the yield increase may be significantly more than 20 per cent;
• Canola leaves a more friable topsoil which is well suited to the direct drilling of the following cereal crop;
• Rotation of herbicide groups reduces the potential for herbicide resistance to develop and for herbicide residues to accumulate in the soil. It also results in better longerterm control of weeds;
• Spreads the time available to use machinery and labour because of canola’s earlier sowing and harvest timing relative to cereals; and
• Provides a range of grain delivery and marketing options. Selling grain off the header at harvest can give growers an early cashflow and reduce on-farm storage demand, while storing or warehousing canola can spread price risk and provide marketing flexibility.

These benefits can result in a more profitable and sustainable farming operation by:

• Consistently producing higher yielding, more profitable cereal crops;
• More diversified income from growing a range of crop types;
• An alternative to cereals with an established and stable marketing system;
• Improved weed control and herbicide resistance management;
• Enabling more efficient use of machinery and labour because of a broader spread of crop preparation, sowing and harvesting operations;
• Reduced competition with wheat and other grains for on-farm grain storage as canola is not usually stored on farm; and
• Providing a range of marketing options to manage price risk.

There is not one ideal rotation that will fit every farm. A rotation should be tailored to your individual situation and forward planning can let you incorporate options in your program to reduce your risk from weeds, pests and diseases. A good rotation may include a pulse, cereal, oilseed, summer/winter season crops, and even forage. The most efficient rotation is one where disease, weeds and the risk of production failure can be minimised while fertility and profitability are maximised.

Reference: Australian Oilseeds Foundation, ‘Crop rotation and paddock selection’ : 71_GRDC_Canola_Guide_Crop_rotation__and__paddock_selection.pdf (australianoilseeds.com)

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