Browsing by Author "Yadvinder Singh"

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How extensive are yield declines in long-term rice-wheat experiments in Asia?
(2003) J.K. Ladha; D. Dawe; H. Pathak; A.T. Padre; R.L. Yadav; Bijay Singh; Yadvinder Singh; Y. Singh; P. Singh; A.L. Kundu; R. Sakal; N. Ram; A.P. Regmi; S.K. Gami; A.L. Bhandari; R. Amin; C.R. Yadav; E.M. Bhattarai; S. Das; H.P. Aggarwal; R.K. Gupta; P.R. Hobbs
The rice-wheat cropping system, occupying 24 million hectares of the productive area in South Asia and China, is important for food security. Monitoring long-term changes in crop yields and identifying the factors associated with such changes are essential to maintain and/or improve crop productivity. Long-term experiments (LTE) provide these opportunities. We analyzed 33 rice-wheat LTE in the Indo-Gangetic Plains (IGP) of South Asia, non-IGP in India, and China to investigate the extent of yield stagnation or decline and identify possible causes of yield decline. In treatments where recommended rates of N, P and K were applied, yields of rice and wheat stagnated in 72 and 85% of the LTE, respectively, while 22 and 6% of the LTE showed a significant (P < 0.05) declining trend for rice and wheat yields, respectively. In the rice-wheat system, particularly in the IGP, rice yields are declining more rapidly than wheat. The causes of yield decline are mostly location-specific but depletion of soil K seems to be a general cause. In over 90% of the LTE, the fertilizer K rates used were not sufficient to sustain a neutral K input-output balance. Depletion of soil C, N and Zn and reduced availability of P, delays in planting, decreases in solar radiation and increases in minimum temperatures are the other potential causes of yield decline. A more efficient, integrated strategy with detailed data collection is required to identify the specific causes of yield decline. Constant monitoring of LTEs and analysis of the data using improved statistical and simulation tools should be done to unravel the cause-effect relationships of productivity and sustainability of rice-wheat systems. © 2002 Elsevier Science B.V. All rights reserved.
Trends of climatic potential and on-farm yields of rice and wheat in the Indo-Gangetic Plains
(2003) H. Pathak; J.K. Ladha; P.K. Aggarwal; S. Peng; S. Das; Yadvinder Singh; Bijay Singh; S.K. Kamra; B. Mishra; A.S.R.A.S. Sastri; H.P. Aggarwal; D.K. Das; R.K. Gupta
Rice and wheat are the two most important cereals in the Indo-Gangetic Plains (IGP) and are responsible for the food security of the region. To understand the productivity trends in the transects of the IGP: (1) the climatic potential yields of rice and wheat were simulated using a crop simulation modeling approach and (2) the long-term trends of potential and on-farm yields were compared. The potential yields of rice and wheat in the IGP ranged from 7.7 to 10.7 and 5.2 to 7.9 Mg ha-1, respectively. The upper transects of the IGP are more productive and yield decreases by 27% for rice and by 32% for wheat from transect 2 to transect 5. The rate of change in the potential yield trend of rice from 1985 to 2000 ranged from -0.12 to 0.05 Mg ha-1 per year. Negative yield trends were observed at six of the nine sites, four of which were statistically significant (P < 0.05). The decrease in radiation and increase in minimum temperature were the reasons for the yield decline. The potential yield trend of wheat, however, appeared to be stable. On-farm yields of rice also showed a negative trend but for wheat the trend was mostly positive. The adverse changes in the weather parameters and declining trends of potential and on-farm yields of rice should be taken as an indication of a future problem. Regular on-farm monitoring of crops and climatic factors is urgently needed for predicting problems and allowing measures to be taken to improve productivity. © 2002 Elsevier Science B.V. All rights reserved.