Despite the title this really a guide to growing any crop as all good crops are the result of good preparation, good planning and good execution. In Australian dryland cropping the yield potential of a crop is already capped before the first seed is sown, our yield is limited by the moisture that is available to the crop during the fallow in the growing season. Everything we do from the start of the fallow onwards affects yield and the best case that we can hope for is that is doesn’t reduce yield. And there are many things that can lead to a reduction in yield including insufficient nutrition, poor fallow management. weed competition, herbicide damage, poor plant stand, disease, wrong time of sowing and unfavourable environmental conditions. However all these issues can be addressed with with planning and preparation.
As we operate in a moisture limited environment and the amount of moisture that is available to a crop is our biggest yield factor it is essential that we capture and store as much moisture as possible during the fallow period. Both the amount of ground cover and effective weed control are big drivers of fallow efficiency. The more ground cover you have you have the better your fallow efficiency will be and the more moisture you’ll have. This is why it is essential to maintain as much stubble as possible and avoid the burning or cultivation of fallowed paddocks whenever possible. If a fallow is after a low residue crop like canola, chickpeas or cotton a cover crop should be considered to build up ground cover and increase fallow efficiency. The other factor that can significantly reduce the fallow efficiency is the weed burden during the fallow period.
Weeds are detrimental factor in crop and in fallow but it can be in fallow were they have the most unseen damage, sucking up moisture that would otherwise be saved for coming crop. The effect of a weed burden during fallow is more noticeable during dry years as there is limited in crop rain to compensate, therefore it is critical that good weed control occurs over the fallow. Where possible weeds should be sprayed in preference to cultivation as the spraying of weeds will help to maintain groundcover. (Remember to consult your local agronomist on herbicide choices and use to make sure you’re using the right gear for the right job) When using herbicides in a fallow you should keep in mind the plant back periods and the damage they may cause if not followed.
Stress from herbicide damage can significantly reduce yield and even remove it completely. Herbicide damage can be from a number of causes including residual from the fallow or previous crop, contamination for poorly cleaned spray equipment, drift from other crops or a accidental application of the wrong chemical. This means it is essential that operations are well planned so plant back periods are met, equipment is thoroughly cleaned, sprays are only applied in correct conditions and the correct chemical is being applied to the right paddock. If this all occurs correctly it is unlikely that yield will be reduced.
Crops need to be fed in much the same way that we need to be fed, they require a range nutrients to grow to their full potential and without anyone of these they will not reach their full potential and yield will be lost. With the exception of legumes (which can pull nitrogen from the atmosphere) all plants source their nutrients from the soil and can only access what their roots can reach. They draw the nutrients up the plant and use them to grow plant matter above the ground including the grain that is harvested. Therefore if some form of fertiliser is not being applied to replace lost nutrients the soil will be slowly depleted of nutrients over time. This is why we need to use fertiliser to replace exported nutrients and regularly test the soil to keep track of soil nutrient levels so we can adjust our fertiliser strategy to suit. All of this should be done before a crop is sown.
The sowing of a crop is the most important operation that a grower can undertake if done well it will occur at the right time and produce the right plant stand that will lead to maximum yield potential. However if it is done poorly a range of issues can occur such as a staggered germination or a poor germination which may require a resow and lead to the crop flowering outside of its desired window. A delay at sowing may also cause the crop to be flowering outside of its ideal window leading to an increased risk of heat stress at flowering while sowing early can increase the risk of frost which can also significantly reduce yield. Once the crop is well established the main risks to production are pests, diseases and random climatic events.
Once a crop is sown and established the biggest risks it can face are weed, disease and insect pressure in crop. As we’ve spoken about weed pressure above I’ll focus on insects and diseases here. Plants can be attacked by a range of pests including aphids, mites, grubs and others, some of these just stunt the growth of plants, some spread viruses that affect plant growth and yield while others can chew the plant and their seed pods to bits significantly reducing the yield potential of a crop. While diseases can have a similar effect on the crop and depending on the disease they may either stunt the plants growth or kill off the crop completely. It is best to prevent these diseases from occurring by treating the crop with a fungicide as a fungal disease can not be cured and it can only be prevented from spreading through the use of a fungicide. These may be applied to the seed as seed treatment preplanting or in crop via a foliar application, for more information on fungicides check out my Wednesday Tec Talk. Pests can occur at anytime during the cropping period and may affect the crop from before emergence right up until the end of harvest, there for it is important to regularly monitor the crop for pests and treat them accordingly. Some pests such as aphids and mites can be prevented through the use of a seed treatment that provides systemic protection while others will need to be identified in crop and dealt with using a in crop spray.
Sometimes yield loss can’t be avoided and freak weather events like hail or a unseasonal frost or extreme heat stress will reduce yield or wipe out the crop completely. While little can be done to prevent this from occurring you can time your sowing to minimise the risk of a frost or heat stress. Afterall farming is all about timing.
While there is no secret and perfect method to growing record breaking crops year on year are few things you can do to maximise your chances, the are plan, be organised, be prepared and make sure that you are doing everything you can to conserve moisture and prevent stress to the crop.
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