Konstgödselspridningens kvalitetsaspekt: en studie av sambandet mellan variationer i gödselintensitet och medelavkastning vid kvävegödsling av vete - metoder och modeller

The aim of the project was to find methods and models suitable for describing and/or quantifying - the characteristics of unevenness in fertilizer intensity - any net effect of the characteristics of the fertilizer unevenness. Non-uniform distribution of nitrogen fertilizer was simulated on wheat. The distribution pattern was simulated by defined systematic unevenness in a transverse direction to the direction of sowing. Totally 3312 sown rows after each seed coulter with a length of 3 meters were individually harvested during 1979-1982. The uptake of nutrient was found to be extremely local but the indirect effect of the influence has a wider range. The interaction between plants gives the crop a ’strategy’ to best benefit from placed nutrient. This strategy, however, does not always seem to result in maximizing the quantity of the yield. The studies show that yield depression may be related to the variability of fertilizer intensity. The variability within a relevant locality influencing the growth of a single plant can be expressed by a variance and an autocorrelation function. A description is given of how yield depression can be predicted and how parameters for predicting yield depression can be estimated by non-uniform distribution patterns. Different methods of analyzing the dependence between neighbouring plots were tested. A moving average and a nearest neighbour technique of analyzing the data were used. A proposed method of field-testing fertilizer distributors is to randomly position trays on the field to be fertilized. The trays should be divided into at least two halves or parts to give a measure of the auto-correlation between neighbouring miniplots. Assuming different types of systematic pattern, the auto-correlation function valid within a relevant distance can be estimated.