Nitrogen requirements of rice crop are met from both soil and fertilizers. Because of acute N deficiency in most rice soils, fertilizer N must be applied to meet the crop demand. A field experiment was carried out at Rice Research and Training center (RRTC), Sakha, Kafr El-Sheikh, Egypt during two summer seasons 2011 and 2012 to study the yield and yield component of Sakha 106 rice cultivars as well as nitrogen uptake in rice grains and soil organic matter percentage as affected by integrated use of composted rice straw and urea fertilizers. The treatments derived from the combination of 4 N fertilizer rates (0, 55, 110 and 165 Kg N/ha) and 3 composted rice straw rates (0, 5 and 7 tons composted rice straw/ha).
The obtained results revealed that, panicle weight, number of panicles, and 1000 grain weight and number of filled grains per panicle increased and reached the maximum values when the treatment of 165 Kg N/ha plus 5 tons composted rice straw/ha was applied but the opposite trend was observed with unfilled grains.
From the results under this study, it could be concluded that the application of 165 Kg N/ha plus 5 tons composted rice straw/ha produced the highest grain yield but the application of 165 Kg N/ha plus 7 tons gave the highest straw yields without any significant difference with the treatment of 110 Kg N/ha plus 7 tons composted rice straw for both of rice grain and straw yield.
The obtained data indicated also, that N uptake in rice grain of Sakha 106 was increased when the treatment of 165 Kg N/ha plus 5 tons composted rice straw was applied but N uptake by straw yield increased when the treatments of 165 Kg N/ha plus 7 tons composted rice straw was applied. The percentage of soil organic matter was increased with the addition composted rice straw.
Multiple linear regressions showed that the prediction equation for grain yield was formulated as follows:-
Grain yield = 1.33 + 0.0794 Nitrogen Uptake (2011)
(R2=97.8% and the adj. R2=97.6%)
Grain yield = 1.55 + 0.0798 Nitrogen uptake (2012)
(R2=99.0% and the adj. R2=98.9%)