Effect of sideral fertilizer on the content of humus in the soil

In a long-term experiment, which was laid down in 1971, in 2 bookmarks with an interval of one year, the effect of sideral fertilizer on the humus content in the soil during 6 rotations of an 8-field crop rotation was studied. The soil is sod-medium-podzolic medium loam on a cover red-brown heavy loam with agrochemical indicators of the arable layer before the experiment was laid: рН_KCl 5.0, A_h – 2.7, S – 14.8 mmol/100 g, V – 85.2%, the content of P₂O₅–52, K₂O – 98 mg/kg of soil. In the 6th rotation, instead of manure, a sideral fertilizer – a pea–oat mixture (18 t/ha) was used as an organic fertilizer. In the experiment, the levels of application of mineral fertilizers on different backgrounds were studied using lime (1 + 2 h. a. in the 1st and 2nd rotations of crop rotation), manure (40 t/ha in the 1st and 60 t/ha in the 2nd and 5th rotations), siderate (in the 6th rotations) and without them. Options with fertilizers: 1 – without fertilizers, 5 – N10P10K10, 6 – N20P20K20, 7 – N30P30K30, 8 – N40P40K40, 9 – N50P50K50, 10 – N60P60K60. For 4 rotations of crop rotation (32 years) without applying background fertilizers, the humus content decreased from 2.5 to 1.96–1.92% (by 0.54 and 0.58 abs.%), against the background of manure – up to 2.38%, lime + manure – up to 2.30%. In the 5th rotation on the backgrounds with the introduction of manure, its content on average in 7 variants increased to 2.62 and 2.70%, which was higher than the initial (2.50%) by 0.12 and 0.20 abs.%. In the 6th rotation, the use of pea-oat mixture as a siderate led to a decrease inthe level of humus content by 0.28–0.30 abs.% is reduced by periodic use of manure (once in each rotation) and winter rye straw (2 times in 3–6 rotations).