African Farming went in search of great tips and tactics from some of our leading farmers to get you thinking or hopefully make or save you a bit of money.
Fertiliser prices have rocketed: The price of a widely used product like MAP has almost doubled since 2019. Here are some tips from top soil consultant Neil Miles on cutting your fertiliser bill.
■ Make sure that your soils do not already have enough of the nutrients contained in your fertiliser.
■ Don’t use fertiliser blends containing three or more nutrients when a single-nutrient fertiliser will do.
■ Apply fertiliser correctly and at the right time for plants to make the best use of it. Then apply technology as far as possible.
Test your soil. It’s the only way to know what fertiliser to use, or how much lime or gypsum you need. No farmer would add oil to his bakkie engine without first examining the dipstick. Applying fertiliser without a soil test is the same.
Get sampling right. In the laboratory, only a teaspoonful soil is tested. This represents many thousands of tons of soil. About 80% of all mistakes with soil testing happen because the sample was taken incorrectly. Your fertiliser representative usually takes samples, but you must make sure it’s done correctly – you’re paying for it, after all. Remember, a poorly taken soil sample is usually worse than no sample at all! First, get the depth of the samples right: row crops 150mm; pastures 100mm; tree crops and sugar cane 200mm. Take enough sub-samples for each sample submitted to the lab. This also applies to grid (“precision”) sampling, as discussed below. Use the well-known Beater soil sampler for quick, accurate sampling (see picture below).
Keep long-term soil test records for all the lands on your farm. This allows recommendations to be based on trends rather than single samples and hugely improves the reliability of fertiliser and lime recommendations. Labs, like everyone, make mistakes. Looking at data trends allows you to spot outliers easily (see the example in the table below) and prevents costly mistakes. Long-term trends are crucial when optimising fertiliser efficiencies. Ask your fertiliser company representative to help, so don’t keep changing reps either!
Interpret results correctly. You’ve done the soil test, now what does it mean? Keep in mind that every crop needs certain nutrients to grow well. Think of that engine-oil dipstick again: at the bottom end of the dipstick, markings indicate whether your engine needs oil. Without these markings, you’d have to guess whether or not you need oil. Similarly, with soil tests, you need to know the ‘high’ and ‘low’ levels for each nutrient. Unfortunately, soil-testing services often list ‘sufficient’ levels that are inaccurate, or unscrupulous sales representatives (not all of them!) use these levels to sell you more fertiliser. Make use of experienced agronomists who preferably don’t sell fertiliser. Don’t let fancy maps and colours fool you. Used correctly, grid (GPS-based) soil sampling can help you to use fertilisers and lime more efficiently while optimising your yields. But be careful: some grid-sampling packages offer little value.
Don’t be fooled by 100-page reports filled with fancy maps and colours! Rather ask your service provider some important questions:
■ The size of grids depends on the variability of your soils. For large, uniform cropping fields, a grid size of 10ha could be enough, but for dairy pastures 0.5ha to 1ha will be necessary. If grid sizes are too big, results could be worthless.
■ Stick to the sampling depths listed above.
■ Don’t take a single soil core sample at a designated GPS point. Take at least five to 10 core samples at each sampling position, ideally in a zig-zag pattern and at least 2m apart, thoroughly mixed, and combined into a single sample.
■ Interpret the data with the help of an experienced agronomist. The ‘adequate’, ‘low’ and ‘high’ categories used in grid sampling reports are often way off the mark. Beware of fertiliser blends and speciality products. Avoid habit – rather rely on science. Don’t fall into the trap of “I always plant my crop with 2.3.4” or “I always top-dress my pastures with 1.0.1 in spring”. Well, if soil tests show the potassium in the 2.3.4 and 1.0.1 is not required, rather save by simply using products like MAP or LAN. Dairy pastures, for instance, often have too much potassium. Adding more of it in fertiliser blends not only wastes money, it also reduces the palatability of the pasture! Be careful of speciality products. For example, farmers use expensive potassium sulphate instead of potassium chloride. The reason? Many say chloride is harmful to soils, which is not true. If it were, the use of sodium chloride as a salt source for humans and animals would have been dangerous.
Split nitrogen dressings. Nitrogen (N) is the ‘accelerator pedal’ for crops and pastures but must be managed carefully. Applied nitrogen is easily lost in several ways – washed away by water, through the air or leeched through soil. Usually only about 50% of applied nitrogen makes it to the crop. To stop such wastage, apply nitrogen in split dressings, not as a single large dressing. With maize, for example, don’t apply all the N before or at planting. If your crop needs, say, 150kg N/ha, a quarter to one third could be applied in the planting band. The remainder should be applied in one or two top dressings during the vegetative growth phase. Also, remember to broadcast urea when top-dressing it – don’t apply it in a narrow band, as a lot will be lost to the air.
Email Neil Miles at milesofsoil@gmail.com or visit soilhealth.co.za to find out more.
