Maize yields have skyrocketed. Back in the 1980s and 1990s 10 tons per hectare was exceptional, with the average on dryland typically being between 3 and 6 t/ha. Today 10 t/ha and even more, even without irrigation, are pretty standard, with the record maize yield (irrigated) being in the vicinity of 23 t/ha! These increases are due to improved hybrids and on-farm management practices. Here are a few critical management practices that can help you also achieve high yields.
- Correction of soil acidity problems
This is the cornerstone of profitable crop farming. Acid soils typically have low pH, low quantities of exchangeable calcium and magnesium, high quantities of exchangeable acidity (mainly aluminium) and high acid saturation. The effects of soil acidity on crops often go unnoticed, because the biggest impact is out of sight in the root zone. Roots typically become thick and stubby, without most of the all-important fine roots. High acidity in subsoils also results in a shallow root system. The poorly developed root systems can take up enough water or nutrients and stunt the plants’ growth. Use lime and gypsum to correct soul acidity. Gypsum is used for acidity in the subsoil, below the topsoil. Soils tests will show how much you must use. Work it into the soil a month or two before planting. Send your soil samples at least three to four months before planting to the lab, so you have enough time to order the correct products. Remember, when the crop is growing, there often are no typical leaf symptoms to show you your soils are acidic, in the way other deficiencies like too little N or K show in the colour of the leaves, so you must test your soil in a laboratory. Soil test results are in any event essential for determining the amount of lime and gypsum required to correct the problem.
2. Look for compacted soil layers
Soil compaction can seriously impact your maize yields, and is a bigger problem than most people realise. Crops growing on compacted soils have poor root development. This reduces yields because not enough water and nutrients can be absorbed by these poorly developed roots. Find compacted layers by digging soil pits to see how roots are developing. If soils are compacted, rip to below the compacted layer with a ripper.
3. Jump-starting your crop with starter fertiliser
Starter fertiliser applied in a band close to the seed is very important for getting the crop off to a nice fast start. Starter fertilisers are usually a blend, such as 2.3.4(30)+Zn; however, use soil tests to determine exactly what you need. It’s important that your planter can place the starter fertiliser about 5cm below and to the side of the seed.
4. Make sure your plants germinate at the same time
It’s very important that seed germinates at the same time, and that you have the correct plant population. Gaps in rows with no plants are all too often the reason for poor yields.
Two important things to remember:
■ Plant seeds at the correct depth. Uneven and poor germination are often due to erratic planting depth. Check your planter continually!
■ Only use quality seed from a recognised company or supplier.
5. Use nitrogen topdressings as an “accelerator pedal”
Lime and starter fertiliser can be viewed as the “oil in the engine” for the crop. Topdressings with nitrogen fertilisers from about the fourleaf stage are the “petrol” or accelerator pedal for quicker growth and bigger yields. Nitrogen fertilisers used are usually urea or LAN. How much you use will depend on your soils and what yields you are targeting.
6. Strategic use of chemicals (herbicides, fungicides and insecticides)
Successful crop farmers win the battle against weeds, insects and diseases. This requires correct rates and timing of applications of appropriate chemicals. Regular scouting of fields is also essential. Remember, prevention is always better than cure!
7. Tapping top consultants
There’s an easier way than learning from your own mistakes – especially since they are often very costly! Top farmers, without exception, make use of experienced consultants who guide them in all aspects of managing the crop – especially when it comes to selection of cultivars, how much fertiliser to use, and what chemicals to spray. Such advice is often the difference between success and failure. And when you’ve found good consultants, stay with them! They will develop a knowledge of your farming operations, climate and soils, and prove to be one of your wisest investments! – Neil Miles & Guy Thibaud.