EFFECTS OF IRRIGATION ON YIELDS OF MAIZE (Zea mays L.) IN DIFFERENT CROP ROTATIONS

It was studied in a long-term experiment on chernozem soil, the effect of crop rotation, irrigation, fertilization and plant density on the yield of maize in an extremely dry year in 2007. The yield increment due to irrigation was 3100-4000 kg ha-1in monoculture, 1700-2300 kg ha-1in biculture and 1900-2600 kg ha-1in triculture, respectively. In monoculture, increased fertilizer dosages and plant densities resulted in a significant yield reduction in the non-irrigated treatment (2600 kg ha-1in the control, 2100 kg ha-1in the N240+PK treatment, at a plant density of 80 thousand plants-1). Without irrigation, 40 thousand plants ha-1proved to be optimal in all crop rotations, while maximum yields were obtained at plant densities of 40-60-80 thousand plants ha-1in mono-, bi- and triculture under irrigation, respectively. Under irrigated conditions, the optimum fertilizer dosages were N180-240+PK, N120+PK and N60-120+PK in monoculture, biculture and triculture, respectively. By optimizing the agrotechnical factors, 10-11 t ha-1yield can be realized on chernozem soil irrespective the cropyear effect.