EFFECT OF DISTANCE FROM DRAIN LINE ON WHEAT CROP UNDER DIFFERENT RATES OF NITROGEN FERTILIZATION IN CLAY SOIL

This study was carried out to evaluate the influence of distance from drain line on response of wheat (Giza 168 variety) to different levels of N-fertilizer. Two field experiments were conducted during 2003/2004 and 2004/2005 successive seasons. The experimental field provided with pipe drain network spaced at 20 m. with 1.2 m depth. N-fertilizer in the form of urea was added in three levels (50, 75 and 100 kg N/fed.) at U4 and U2 distance from drain line in two equal doses after the first and second irrigation, respectively.
Results showed that 1000 grain weight (gm), grain yield (ardab/fed.) and straw yield (Heml/fed.) significantly increased as the distance from drain line decreased from U2 to U4 in both studied seasons. These increases were equivalent to 1.37 and 1.16 (gm), 1.43 and 1.89 (ardab/fed.) and 1.69 and 1.3 (Heml/fed.) in the first and second season, respectively. Nitrogen uptake (%) by wheat at booting stage increased by decreasing distance from drain line from L/2 to U4 and the increase was significant in the second season with high wheat yield.
Data also indicated that wheat grain and straw yield significantly increased with increasing applied nitrogen rate up to 100 kg N/fed. in both studied seasons.
Weight of 1000 grain (gm) and nitrogen uptake °/o at booting stage responsed to the increment of nitrogen applied rate with a significant increase at the highest nitrogen rate (100 kg N/fed.).
Results also showed that the interaction between distance from drain line and N-fertilization rate on wheat yield characteristics was positive. The highest values of wheat yield characteristics and N-uptake (%) were obtained at L14 distance from drain line and 100 kg N/fed. applied rate. In the first season, the effect of interaction on increasing wheat characteristics was significant at a rate of 100 kg N/fed., where it significantly increased 1000 grain weight (gm) and wheat grain yield (ardab/fed.) in the second season at the same nitrogen applied rate.
The obtained results revealed also that 20 m spacing in clay soils is not the proper but may be economic. In addition, distance from drain line must be taken into consideration when distributing fertilizer treatments and their replicates in fertilization experiments to obtain reliable results.