DIVERSIFICATION OF CROP ROTATION WITH FIELD PEAS ON NITROGEN USE EFFICIENCY FOR WINTER WHEAT YIELD

Crop rotations that involve plants with additional functions can reduce the use of mineral fertilizers and improve nitrogen (N) use efficiency. The aim of the study was to determine the influence of crop diversification with field peas (Pisum sativum L.), catch crops on winter wheat (Triticum aestivum L.) grain yield and N utilization efficiency. The following crop rotation was studied: 1) spring barley – spring oilseed rape (Brassica napus L.) – winter wheat– winter wheat; 2) spring barley – field pea – winter wheat – winter wheat; 3) spring barley + white mustard (Sinapis alba L.) as catch crop – field pea – winter wheat – winter wheat. Mineral N fertiliser was applied for crop rotation plants: 1) unfertilised, 2) sustainable fertilising and 3) intensive fertilising. The studies also compared and evaluated three Lithuanian pea varieties ‘Ieva DS’, ‘Jura DS’ and ‘Egle DS’. Pea as a preceding crop for winter wheat increased the soil mineral nitrogen (SMN) content by 38.0% compared to rapeseed (as preceding crop). The productivity of winter wheat grown after pea was 888-1056 kg ha-1 higher compared to the winter wheat yield grown after spring oilseed rape. Based on the data of the yield of winter wheat and the N accumulated in that winter wheat, it can be stated that the rate of mineral N fertilisers after legume grains can be reduced by 47 kg N ha-1. The highest efficiency of mineral N fertilizers was determined on the wheat yield sown after pre-sowing pea and sustainable fertilised. After re-sowing winter wheat, grain yield was low, and the pre-sowing effect was small. However, N fertilisers for wheat were particularly effective in both crop rotations of spring oilseed rape and field pea. Pea varieties differed in yield, N accumulation in biomass, and residue content. This affects their value as pre-crops.