| Autor: |
Shukla, Arvind K., Ladha, Jagdish K., Singh, V. K., Dwivedi, B. S., Balasubramanian, Vethaiya, Gupta, Raj K., Sharma, S. K., Singh, Yogendra, Pathak, H., Pandey, P. S., Padre, Agnes T., Yadav, R. L. |
| Zdroj: |
Agronomy Journal; November 2004, Vol. 96 Issue: 6 p1606-1621, 16p |
| Abstrakt: |
Low N use efficiency (NUE) continues to be a problem in the rice (Oryza sativaL.)–wheat (Triticum aestivumL.) cropping system. The leaf color chart (LCC)–based real‐time N management can be used to optimize/synchronize N application with crop demand or to improve existing fixed split N recommendations. We conducted a field experiment during 2001–2003 at Modipuram, India, to determine the threshold LCC values for N application in rice and wheat, assess the need for basal N application, calibrate the LCC with a chlorophyll meter (SPAD), and work out the economics of rice–wheat systems. Treatments consisted of LCC scores of 2 to 5 for different cultivars of rice and wheat and were compared with the zero‐N control and a recommended fixed‐time N splitting. In rice, LCC ≤ 3 for ‘Basmati‐370’, 4 for ‘Saket‐4’, and 5 for ‘Hybrid 6111/PHB‐71’ produced higher yield and NUE than recommended N splits. In wheat, maintenance of LCC ≤ 4 required 120 kg N ha−1, which produced higher grain yield, N uptake, and NUE than that of recommended N splits. Chlorophyll meter reading and crop growth rate (g m−2day−1) at 15 d after transplanting in rice and 21 d after seeding in wheat were not significantly different with or without basal N application, indicating that basal N application in rice and wheat was not necessary in soils having relatively high indigenous N supply. Both LCC and SPAD readings (r= 0.84 to 0.91) were highly correlated in rice and wheat. Net returns were 19 to 31% higher in LCC‐based N management than in fixed‐time N application for rice–wheat cropping. |
| Databáze: |
Supplemental Index |
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