The study was designed to investigate the effect of cold irrigation water on rice growth and on uptake of N, P, K and Zn applied ca. 50, 20, 35 and 5 mg kg−1 soil, respectively. Cold temperature of irrigation water reduced rice shoot and root dry weight and plant height, significantly compared to hot temperature treatment. Under low temperature stress N was a major rice growth determinant. Increased shoot concentrations of both P and Zn allevated the low temperature stress. The uptake of N, P, K and Zn reduced significantly at low temperature (16.5–20 °C soil and 20–24 °C flood water) compared to high temperature (24.5–27 °C soil and 26.5–29.0 °C), with the strongest effect being noticed for N, followed by P, K and Zn. Application of N, P, K and Zn increased their uptake in rice shoots. Nitrogen and K had synergistic effect on their uptake. Responses to N and K application and their uptake behavior were well marked at higher than at low temperature whereas reverse was true for P and Zn.

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With a view to develop simpler techniques for improving the efficiency of nitrogen fertilizer use for lowland rice, field studies were conducted in 1986 and 1987. During 1986, dry soil incorporation of urea was compared with puddled soil application of urea and calcium ammonium nitrate (CAN) and deep placement of urea super granule (USG). In 1987, the application of urea in puddled soil without standing water (soil saturation) was compared with the application in standing water and deep placement of USG. The results revealed that deep placement of USG and dry soil incorporation of urea were comparable in their effect on the increase of the number of productive tillers, straw and paddy yield, and agronomic efficiency. Consequently N utilization and recovery efficiency were higher with these methods of fertilizer application than with the application of urea and CAN in puddled soil. Application of urea fertilizer under soil saturation conditions and deep placement of USG were found to be comparable in the production of tillers, straw and grain yield and both gave similar agronomic and N recovery efficiencies to the application of urea on the Miranpur soil under standing water conditions.

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