Effects of Uneven Fertiliser Spreading – A Literature Review.
In modern agriculture fertilisers have to be applied as quickly and evenly as possible over increasingly wider bout widths.
This paper reviews the literature on the effect of spreading pattern on crop yield as dependent on fertiliser yield response and gives examples of conditions under which marked yield losses may occur due to uneven fertiliser distibution.
Dr K Dilz, Institute for Soil Fertility, Haren, Netherlands.
G D van Brakel, Institute of Agricultural Engineering, Wageningen, Netherlands.
Effects of Inaccurate Fertiliser Spreading on Crop Yield and Quality in the UK
The UK fertiliser market has a farm delivered value of around £950 million and it is estimated that fertiliser use is responsible for some £3 billion of agricultural output (1985 values). Inaccuracy in fertiliser application is, therefore, important on a national as well as farm scale.
Two types of inaccuracy occur – incorrect rate of application and uneven spreading. Applying the correct rate of fertiliser depends on accuracy in predicting the optimum rate and precision in achieving it once predicted. Errors are likely to be greatest in prediction and may often be in the range 20-50%. Uneven spreading can be a result of spreader design, fertiliser properties or, more usually, spreader maintenance and operation. Published field tests have shown coefficients of variation (CV) of up to 40% in fertiliser application though 20% is more typical.
Estimates of the effect of uneven spreading on yield are provided by combining mathematical functions describing unevenness of spreading with those relating crop yield to fertiliser rate. Form of the yield response function has a marked effect on yield loss estimates. For an exponential type response, a CV of 20%, compared to even spreading, results in a yield loss of 20 kg/ha to 50 kg/ha in cereals. Similar financial losses were estimated for oilseed rape, sugar beet and grass for silage.
In practice, there will be errors both in application rate and in evenness of spread. It appears that application rate errors will often have the greatest effect on crop yield but that unevenness of spreading may cause the greatest financial loss.
Dr I R Richards, Norsk Hydro Fertilizers Ltd., Levington, UK.
52 pages, 17 figures, 26 tables, 53 references