Contents & Foreword, Characterizing And ... - IRRI books

1. There are possibilities of growing a second crop after rice with the conservedmoisture and nutrients.2. Though the productivity of a second crop (chickpea or linseed or lathyrus) ishigher in short-duration rice fields than in medium-duration rice fields, theoverall rice equivalent productivity of the crop sequence (total cash value ofproduce from both the crops, based on prevailing price) is higher in the caseof medium-duration rice followed by a second crop, indicating that this systemis more suitable.3. The rice equivalent productivity (cash value) of chickpea produce is higherthan that of either lathyrus or linseed.Table 5 indicates that in general chickpea yield was higher in the short-durationrice-chickpea crop sequence, but the average total income in this sequence is Rs16,230,whereas, in the medium-duration rice-chickpea crop sequence, the average total incomeis Rs20,784. It is therefore recommended that, in view of the higher productionpotential, the medium-duration rice-chickpea system should be followed in heavy(black) soils of the drought-prone lowland rice ecosystem. Year-to-year fluctuationsin the productivity of both crops occur, however. During 1996-97, which happened tobe a severe drought year, the chickpea crop could not be sown due to dry soil conditionsand the rice yields were the lowest of the four years. The period 1995-96 was agood rainfall year and both the chickpea and rice yields were the highest of the fouryears. A risk analysis on the cropping systems over time is essential in such cases.In drought-prone lowland ecosystems, the ill effects of drought can be alleviatedwith timely and proper crop management practices. In the on-farm experimentsconducted at Raipur during 1995-96 to 1998-99, the highest, lowest, and median riceproductivity across fields and its standard deviation are shown in Table 6.Table 6 shows that, even in bad (drought) years such as 1996, the highest yieldsof rice varieties Mahamaya and Poornima were 3.6 and 2.7 t ha –1 , respectively, whereastheir lowest yields during 1996 were 1.8 and 0.4 t ha –1 , respectively. Such a variationin yields across fields is a clear indication of crop management differences, which inthis case were mainly related to the timeliness of crop establishment, “beushening”(dry-sown crop then plowed and laddered 30–35 d after sowing with 10–15 cm ofstanding water), and weed control operations. The beneficial effects of proper managementcan also be realized even in good rainfall years such as 1995 (Table 6).An analysis of the dry weeks (weeks receiving less than 50 mm rainfall) indicatesthat 1999 had a continuous dry spell of 10 wk from 27 August to November, thatis, from the 35th to the 44th standard meteorological week (SMW). This resulted insevere drought conditions. In light soils, the rice crop failed completely. In heavysoils, some farmers provided a small supplementary life-saving irrigation from thewater collected in roadside ditches, which benefited those farmers considerably (Table7).Technologies for the submergence-prone rainfed lowland ecosystemThe agroecological analysis of rainfed lowland rice areas in Jorhat District of Assamindicated that submergence proneness was one of the major causes of low and un-Planning and managing rice farming through environmental analysis 205