Cultivar, Nitrogen, and Water Effects on Productivity, and Nitrogen-Use Efficiency and Balance for Rice- Wheat Sequences of Bangladesh
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Date
2001-06-12
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Abstract
Rice (Oryza sativa L.) and wheat (Triticum aestivum L.) are often grown in sequences under a range of nitrogen (N), water (W), and planting date in South Asia. Field experiments were conducted from 1994-1995 to 1996-1997 to define the effects of two W and three N regimes on growth and productivity, N uptake and Nouse efficiencies, and N halance for rice-wheat systems of northern Bangladesh. Mean grain yields of rice and wheat were greatest (4.9 and 3.1 t ha", respectively) during the first and smallest (2.2 and 241 ha respectively) during the third year. The cuhivars of rice and wheat responded to imigation and to N, with greater response to irrigation in rice, but to N in wheat. Delayed wheat seeding redaced wheat yields in all years. Agronomic N-use efficiency (kg grain yield per kg N applied), physiological efficiency (kg grain yield per kg N ahsurbed), and fertilizer N-recovery efficiency (kg N absorbed per kg N applied, expressed as ) for rice across treatments ranged from 2.8 to 10.8, 5.2 to 27.5, and 33 to 61, respectively, and all were greater for N application at 90 compared with 135 kg Nha For wheat, those values ranged from 15 to 27, 33 to 51, and 45 to 63, respectively, and were greater at 120 compared with 180 kg Nha, and under irrigation than rainfed. All those parameters had greater values under irrigation than rainfed. Total soil N increased slightly after 3 years of cropping, while organic carbon and plt decreased slightly in all treatments. There was a net increase of soil ammonium N (80 kg ha) and a zero balance of N after the fest year of cropping under imgation with high N (135 and 180 kg ha for rice and wheat, respectively), but without N there was a decrease of soil mineral N (70 kg ha) with a balance of +16 kg ha. Biological N fixation accounted for N halance in N-omitted as well as N-applied treatments. The results emphasize the need for regular monitoring of weather, crop performance, imgation water, and soil and plant mineral N for further understanding the growth, productivity, N-use efficiencies, and balance in rice-wheat system.
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Keywords
Water, Nitrogen, Cultivators, Productivity
Citation
Timsina, J., U. Singh, M. Badaruddin,C. Meisner and M.R. Amin. 2001. “Cultivar, Nitrogen, and Water Effects on Productivity, and Nitrogen-Use Efficiency and Balance for Rice- Wheat Sequences of Bangladesh,” Field Crops Research, 72:143-161.