Carbon sequestration in tropical soils has potential for mitigating global warming and increasing agricultural productivity. We analyzed 26 long-term experiments (LTEs) in different agro-climatic zones (ACZs) of India to assess the potential and cost of C sequestration. Data on initial and final soil organic C (SOC) concentration in the recommended N, P and K (NPK); recommended N, P and K plus farmyard manure (NPK + FYM) and unfertilized (control) treatments were used to calculate carbon sequestration potential (CSP) i.e., capacity to sequester atmospheric carbon dioxide (CO 2) by increasing SOC stock, under different nutrient management scenarios. In most of the LTEs wheat equivalent yields were higher in the NPK + FYM treatment than the NPK treatment. However, partial factor productivity (PFP) was more with the NPK treatment. Average SOC concentration of the control treatment was 0.54%, which increased to 0.65% in the NPK treatment and 0.82% in the NPK + FYM treatment. Compared to the control treatment the NPK + FYM treatment sequestered 0.33 Mg C ha −1 yr −1 whereas the NPK treatment sequestered 0.16 Mg C ha −1 yr −1. The CSP in different nutrient management scenarios ranged from 2.1 to 4.8 Mg C ha −1 during the study period (average 16.9 yr) of the LTEs. In 17 out of 26 LTEs, the NPK + FYM treatment had higher SOC and also higher net return than that of the NPK treatment. In the remaining 9 LTEs SOC sequestration in the NPK + FYM treatment was accomplished with decreased net return suggesting that these are economically not attractive and farmers have to incur into additional cost to achieve C sequestration. The feasibility of SOC sequestration in terms of availability of FYM and other organic sources has been discussed in the paper.
Increasing temperature is likely to affect productivity of wheat and chickpea crop. A field experiment was conducted for two consecutive years with wheat and chickpea crop raised inside the temperature gradient tunnel (TGT). Results showed that high temperature reduced crop growth duration in both the crops. Days to 50 % flowering reduced by 4-5 days in wheat with 1.8-2.9°C increase in temperature. Photosynthesis rate, stomatal conductance and leaf area index reduced with the rise in temperature. High temperature inside the TGT caused reduction in both biomass and grain yield of wheat crop in both the years and the reductions in yield per degree temperature rise was 10.4-10.5 % in wheat crop. Number of spikes per plant, number of grains per spike, 1,000 seed weight was also affected with increased temperature. In case of chickpea crop, yield declined with the increase in temperature during the [2008][2009] year and the decline per degree temperature rise was 6.8 %. During the year 2007-2008, 1.7°C increase in temperature showed improvement in biomass and grain yield in chickpea. Low air temperature during the crop growth period in 2007-2008 could be responsible for increased growth of chickpea under high temperature. This suggests that rise in temperature in future climatic change scenario will adversely affect wheat and chickpea crop but the response will be crop and region specific depending upon the existing climate conditions.
Increased temperature due to global warming may reduce pollen germination and induce spikelet sterility in rice crops. Anthesis is the most sensitive stage in rice and exposure to high temperature during this period may cause reduction in floral reproduction. Increased temperature will have different effects on different rice varieties. In the present study the effect of high temperature on pollen as well as on spikelet sterility in basmati (aromatic) and non-basmati (non-aromatic) rice varieties was quantified. Rice varieties were grown at 11 different sowing dates, to see the effect of varying temperature on pollen and spikelet sterility. Rise in temperature increased pollen sterility and reduced germination of pollen grains on the stigma. Temperature above 338C during anthesis gradually increased pollen sterility in all rice cultivars. At 35.58C, variety Pusa Sugandh 2 (basmati) recorded a pollen sterility of 17% and 26% reduction in pollen germination. The principal cause of sterility was reduced anther dehiscence and less pollen deposition on the stigma at higher temperature. Increased temperature during the grain-filling period also increased spikelet sterility in rice and variety Pusa Sugandh 2 was most affected. Nonbasmati rice varieties were less affected by increased temperature than basmati types. The study indicated that increasing temperature could limit rice yield by affecting pollen germination and grain formation. It also suggested that sensitivity of pollen grains to temperature damage could be taken as one of the most important parameters for predicting rice yield in warmer climates.Additional keywords: pollen sterility, basmati rice.
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