Irrigation and Yield Parameters of Soybean as Effected by Irrigation Management, Soil Compaction and Nitrogen Fertilizationy

Irrigation parameters (reference crop evapotranspiration, actual plant water use, amount of irrigation water, water use efficiency, irrigation water use efficiency, plant water consumption coefficient, variations in soil moisture based on plant water consumption-amount of irrigation water) and yield parameters (seed yield, 1000-kernel weight, harvest index) were investigated for soybean grown in Harran Plain under conventional every-furrow and alternate-furrow irrigation management systems, three different compaction levels (control without compaction, low compaction, high compaction) and three different nitrogen levels (6, 9, 12 kg da(-1)). Experiments were carried out during 2006 and 2007 cropping seasons in Sanliurfa, Turkey in split-split plots experimental design with 3 replications. Irrigation program was created by KanSched simulation model. The amount of applied irrigation water in conventional and alternate furrow systems in 2006 and 2007 were measured as 435.61 and 291.59 mm, and 429.51 and 271.72 mm, respectively. ET values decreased with increasing compaction levels. The highest ET value (568 mm) was observed in non-compacted control treatment and the lowest value (240 mm) in high-compaction treatment. Irrigation water use efficiency increased with decreased irrigation water and the values were higher than water use efficiencies. While the highest yield (94.78 kg da(-1)) was observed in control treatment of the year 2006, conventional furrow system had the highest yield (209.93 kg da(-1)) in the year 2007. While effects of compaction and irrigation on harvest index were insignificant, nitrogen doses were found to be significant. Results revealed that KanSched irrigation model could be used for irrigation scheduling but plant coefficients to be used in the model should be determined properly based on climate conditions. Negative impacts of soil compaction in agricultural fields due to traffic and various other reasons can be eliminated with proper irrigation and fertilization implementations. However, yield losses at high-compaction levels may reach up to 45%