Residual effects of perennial grasses as green manure on soil agrochemical properties and spring barley

Field experiments were carried out at the Vezaicai Branch of the Lithuanian Institute of Agriculture on an Albi-Endohypogleyic Luvisol (LVg-n-w-ab). The study was aimed to explore the residual effect of phytomass of differently-managed perennial grasses, as green manure, on the improvement of soil properties and on the productivity and phytopathological condition of spring barley grown in a crop rotation in the second year of effect. The greatest amounts of plant residues were found to be left in the soil after differently-managed lucerne (19.48 and 17.29 t ha(-1)) and red clover of the 2nd year of use (13.06 t ha(-1)). With phytomass, the soil received 294.6, 262.6 and 228.2 kg ha(-1) of nitrogen, 31.0, 26.5 and 24.8 kg he of phosphorus, and 154.2, 133.6 and 129.3 kg ha(-1) of potassium, respectively. The C:N ratio of the aboveground mass of perennial grasses was the lowest and more favourable for a more rapid decomposition (10.0-14.0) than in the residues (roots and stubble) (20.0-36.0). Nutrients, released during mineralization of phytomass of perennial grasses of the second year of use, had a positive effect on spring barley grown in the second year of effect after green manure incorporation. The correlation of spring barley total stem number, productive stern number and grain yield with the content of organic carbon formed by perennial grasses was moderately strong and strong (r = 0.504*, 0.640** and 0.727**, respectively). The correlation of spring barley productive stem number and grain yield with the content of available phosphorus formed by perennial grasses was moderately strong and strong (r = 0.506* and 0.790**, respectively). Available potassium content in the soil influenced only barley grain yield r = 0.548*. The severity of spring barley foliar diseases significantly depended on the growing conditions: P < 0.05. A 1.1-1.2-time higher foliar disease incidence and severity was recorded in the agrocenoses of spring barley after legumes of the 2nd year of use, especially after lucerne. The total and productive stern number of spring barley significantly increased the severity of foliar diseases at barley booting and milk maturity stages (r = 0.455*, 0.502*, 0.905** and 0.834**). However, the severity of foliar diseases did not exert any significant impact on barely grain yield and 1000 grain weight.