The effect of plant-based organic fertilisers on the yield and nitrogen utilization of spring cereals in the organic cropping system

Legumes in stockless cropping systems are the key elements for nitrogen (N) supply, nutrient cycling, crop productivity and soil fertility. Field experiments were conducted in 2015-2017 on the loam and clay loam soil at two experimental locations in Lithuania. The aim of the research was to study the two-year effect of technologically processed plant-based organic fertilisers on the mineral N (N-m(in)) and mobile humic substances in the soil, also the productivity and N accumulation by spring cereals in the organic cropping system. The following fertilisers were investigated: fresh mass of red clover, fermented red clover mass, fermented pea and wheat mass, composted red clover and wheat straw mass and granulated cattle manure. Fresh and fermented red clover mass was found to be rich in N and potassium (K), while composted red clover and straw mass was rich in phosphorus (P). Soil N-min was significantly increased by the fresh red clover mass in the 1st experimental year and by fermented red clover mass in the 2nd year, and significantly correlated with carbon to nitrogen ratio (C:N) of plant-based fertilisers. In the 1st year, the grain yield of spring wheat was significantly increased using fresh red clover mass and granulated cattle manure; however, in the 2nd year fermented red clover mass increased the yield of spring barley grain the most. During the two years of plant-based organic fertiliser use, in both experimental sites most of the N yield in cereal grains and straw was accumulated using fresh red clover, fermented red clover and granulated cattle manure fertilisers. Comparison of the two experimental sites revealed that the effects of plant-based fertilisers on the productivity of cereals and changes in soil chemical compounds were more apparent in the N-min low loam soil than in the N-min richer clay loam soil. The effect of fermented red clover and granulated cattle manure was comparable; however, greater improving effect was exhibited by the fermented red clover in the loam soil and by granulated cattle manure in the clay loam soil.