Soil testing benefits

Why & how?

We recently published the first two parts of our soil series, explaining why our specialists recommend soil testing and how Members can test their soils, using both low and high tech methods.

The third and final part of this trinity seeks to share the benefits of soil testing, with case studies of UK farmers who have improved their overall production with the assistance of soil testing.

Beef farm became self-sufficient for feed

Our first example is a suckler beef farm in south west Wales, where a regular programme of testing soils has provided the information needed to ensure that nutrient inputs provide all the requirements for grazing land and cereal crops. The farm has 155 Continental-cross cows and since the 1980’s have tested their soils every three years. The results inform the nutrient inputs on the 480 acre farm.

Although primarily grassland the farm produces 100 acres of winter barley and fodder beet some of which is sold and some used as feed for youngstock. All animals are outside for 10-11 months each year, which is achieved by winter-grazing the herd on forage with no silage or straw supplementation.

The cows are housed at the end of January before calving. Calves are reared as stores and sold at market. As the kale forage is a crop which absorbs high levels of phosphate they have to make sure they put enough back into the soil to support the spring barley and the fodder beet. The soil is mostly loam over shale, and so they aim to keep the potash and phosphate indices at 2 and lime at 6.5-7 but the soil test results sometimes point to shortfalls.

In total 20 samples are taken in the autumn and the results showed that 80% of the soil had the correct level of nutrients. In this part of Wales it is traditionally the lime that is below required levels.

The farmer say it is a short-sighted approach to not prioritise soil testing. “We test to get the best out of our soil. You will never achieve productivity if you don’t keep indices in the right place. Although there is a cost to testing, it is cheaper in the long run because you are adding nutrients in the right quantities and growing better crops.” 

Higher yields with less nitrogen

A farmer in the North West of England has increased his spring malting barley yields by 10% while cutting his nitrogen fertiliser use by some 15%. They carried out a small farm based trial to fine-tune fertiliser timings with an aim to improve yield and still make malting grade. Following the success of the trial this new regime has been expanded to 30% the crop.

The farm trial led to a reduction in nitrogen use from 103kg/ha to just 91kg/ha, and resulted in yields growing from 5.97t/ha to 6.49t/ha while adding over £100/ha margin over fertiliser costs.

Malting barley is a very important crop on this study farm, being nearly 25% of the cropped area. Usually it gives a grain nitrogen of 1.6-1.8% and is suitable to produce malt, and yields about 6t/ha. The trial demonstrated that they could push up yields, cut back on fertiliser and still make malting grade, with the added advantage that the amount of ears falling was reduced.

The trial field was tested for nitrogen to give a soil nitrogen supply of 64kg/ha, and so a further 90kg/ha of nitrogen was recommended to achieve a yield of 7t/ha. The nitrogen was applied via one application of a granular N-P-K-S compound for half of the nitrogen in the seedbed, followed by another 45kg/ha of nitrogen from ammonium nitrate at first leaf, making the dose up to 90kg/ha.

This farmer also believes that nitrogen recovery and utilisation is far better when applying P and K in the spring, so that they are immediately available for the crop.

How can AF help

You can contact your AF Crop Inputs team by email to agronomy@af.farm or call 01603 881 906, and they will advise the best test for you depending on your requirement and your geography. AF specialists can also then help plan your nutrient inputs for the coming season.

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