The effectiveness of fertilization and rotation on yield and quality of irrigated maize

The effect of chemical and organic fertilization on the irrigated maize yield and on some chemical characteristics of the soil was surveyed in a 4 year crop-rotation during 1972-1983, on a leached meadow chernozem at Girisul de Cris, district of Bihor. On a non-fertilized soil, the maximum yields of 105,6 q/ha in the first production cycle and 115,8 q/ha in the second and third one were obtained by the application of P150, N210, respectively. The highest economical yield of 108,6 and 119,5 q/ha respectively, were obtained by the application of P100, N210 during the 3 rotation cycles, on a soil with organic fertilization. As a result of the long term fertilization and of adequate crop-rotation, the average yields per rotation cycle increased from 92,1 to 97,2 q/ha and 103,2 q/ha respectively, on a mineral soil and from 99,7 to 103,5 q/ha and 111,6 q/ha respectively from the first to the second and the third rotation cycle on an organic-mineral soil. The high grain yield increase, obtained per 1 kg fertilizer was between 8,6 and 21,2 kg grains when nitrogen was applied and between 6,7 and 17,6 kg when both nitrogen and phosphorus were applied, whether organic fertilizers were present or not. This proves a good economic efficiency of complex fertilization in irrigated maize. Due to complex nitrogen and phosphorus fertilization (for a long time), the organic matter content of the soil in the ploughed layer preserved the initial level with a slight tendency to increase, while on the organic mineral soil a significant increase of 0,15-0,26% was recorded. As a result of the application of the complex fertilization system, a favourable modification of the mobile phosphorus content in the soil was recorded, reaching from an initially very low supply level (18-27 ppm) to an almost very good one (57-70 ppm). By long time fertilization with high nitrogen and phosphorus dosage rates, a very significant acidification of the soil by 0,14-0,48 pH units was recorded. Acidification decrease was lower on a soil with organic fertilization.