Wet Season Rice Research Articles

Farmers’ Management Practices and Grain Yield of Rice in Response to Different Water Environments in Kamping Puoy Irrigation Rehabilitation Area in Northwest Cambodia

The farmers’ management practices and grain yield were examined in the consecutive 4 cropping seasons from wet season rice (WSR) in 2008 to dry season rice (DSR) in 2010 across upstream, midstream and downstream fields, along two secondary drainage canals (located either upstream or downstream side along the main canal) in the Kamping Puoy Irrigation Rehabilitation area (KPIR). In WSR, standing water depth was much deeper in downstream fields where medium and late maturing varieties were planted from May than in upstream fields where early and early medium maturing varieties were planted later (mostly in July and August). In DSR there was less difference in water conditions between upstream and downstream fields and variation in planting and harvesting time was small. As the area percentage of fields where DSR was introduced increased from 2008 (54%) to 2010 (100%), planting time in WSR was later (e.g., from May to July) with declining proportion of dry seeding method and mid-season tillage. Grain yield was low in DSR, particularly in 2010 (287 and 247 g m-2 in 2009 and 2010 on average, respectively), due to insufficient weed control and small amount of fertilizer, and the yield was lowest in fields which practiced DSR for the first time. Grain yield in WSR (286 and 291 g m-2 in 2008 and 2009 respectively) increased by transplanting, use of high yielding Raing Chey variety, and application of a larger amount of N chemical fertilizer. These findings indicated that the agriculture extension support to farmers, particularly in DSR, is a key important factor for rice yield improvement in KPIR.

Flanking Microsatellite Markers for Breeding Varieties Against Asian Rice Gall Midge

The Asian rice gall midge, Orseolia oryzae Wood-Mason (Cecidomyiidae: Diptera) is a serious pest of wet season rice in South and Southeast Asia. Due to internal feeding habit and presence of biotypes of the pest, the most feasible way to control is breeding varieties resistant against multiple biotypes through marker-assisted breeding (MAB). But very few versatile co-dominant markers linked to the gall midge resistance genes are available. We used a set of F9 recombinant inbred lines (RILs) of the cross TN1/PTB10 and identified microsatellite markers for the gall midge resistance gene in cv. PTB10 on short arm of rice chromosome 8. Markers RM22550 and RM547 flank the gene at a distance of 0.9 and 1.9 cM, respectively. Amplification of the markers in gall midge resistant and susceptible cultivars showed that these markers can be successfully used in MAB for development of gall midge resistant varieties.

Monitoring transplanting operation of rice crop using passive microwave radiometer data

This study highlights a methodology to detect the transplanting operation of wetland rice at a regional scale using SSM/I brightness temperature in frequencies like 19, 37 and 85 GHz with vertical polarization. A cloud removal algorithm was used to make weekly composites of the brightness temperature, which were used to estimate the soil wetness index (SWI). Flooding of rice fields with water for transplanting induces very high change in SWI due to contrasting dielectric constant of water (80) and soil (4). Different weather conditions and fractional wet area under the footprint of sensor affect SWI, hence absolute value of SWI was not adequate. Therefore, multi-year SWI anomaly was used to generate a threshold value of SWI change to detect when SWI change between two consecutive weeks was an indicator of transplanting. A minimum SWI increment of 6 between two successive weeks was determined to be an optimal threshold value to detect transplanted fields. Based on the SWI threshold, five transplanting periods (standard meteorological week 21–25) were observed over a large area (Punjab and Haryana states) in the Indo-Gangetic plains of India. The cumulative areas under different rice transplanting periods were of 14%, 19%, 37%, 53% and 100% for the standard meteorological weeks 21, 22, 23, 24 and 25, respectively. The results were validated for the 2007 wet season rice crop. Estimated rice transplanting periods using SSM/I data were found to be in good agreement (90%) with the ground truth observations in the study area.

Knowledge, attitudes and practices of farmers on rodent pests and their management in the lowlands of the Sierra Madre Biodiversity Corridor, Philippines

A survey of the knowledge, attitudes and practices (KAP) of 100 rice farmers and 50 coconut farmers was conducted in the coastal lowland agro-ecosystems of the Sierra Madre Biodiversity Corridor, Luzon, Philippines to identify current rodent management practices and to understand the extent of rat damage and the attitudes of farmers to community actions for rodent management. Pests were most commonly listed as one of the three most important rice and coconut production constraints. Other major crop production constraints were typhoons and insufficient water. Farmers consider rats to be the major pest of coconut and of rice during the wet season rice crop, with average yield losses of 3.0% and 13.2%, respectively. Rice and coconut farmers practised a wide range of rodent management techniques. These included scrub clearance, hunting and trapping. Of the 42 rice farmers and 3 coconut farmers that applied rodenticides to control rodents, all used the acute rodenticide, zinc phosphide. However, only ten rice farmers (23.8%) applied rodenticides prior to the booting stage and only seven farmers (15.6%) conducted pre-baiting before applying zinc phosphide. The majority of farmers belonged to farmer organisations and believed that rat control can only be done by farmers working together. However, during the last cropping season, less than a third of rice farmers (31.2%) applied rodent management as a group. In order to reduce the impact of rodents on the farmers of the coastal lowlands of the Sierra Madre Biodiversity Corridor, integrated management strategies need to be developed that specifically target the pest rodents in a sustainable manner, and community actions for rodent management should be promoted.

Biology of the African rice gall midge Orseolia oryzivora (Diptera: Cecidomyiidae) and its incidence on wet-season rice in Nigeria

The biology of the African rice gall midge Orseolia oryzivora Harris and Gagne was investigated in screenhouse and laboratory studies, and its incidence on cultivated wet-season rice was studied in farmers’ fields during the 2006 and 2007 rice-growing seasons at two localities in Nigeria. This insect is nocturnal, and mating takes place immediately after emergence. Both mated and unmated females lay eggs, with mated females laying on average 389 eggs each, and unmated females laying about 87 sterile eggs. The egg stage takes on average 2.5 days. Larval development takes 3.6, 3.3 and 3.0 days for the first, second and third instars, respectively, while the pre-pupal and pupal stages take 2.8 and 6.1 days, respectively. Adult females live for 48–78 h, while males live for 24–30 h. The life cycle of O. oryzivora is completed within 21–24 days under screenhouse conditions. The adult male is slender and about 3 mm long, while the female is more rounded with a 4 mm long body and a bright red abdomen. The insect produces unisexual progeny. Field incidence is low at the beginning of the rainy season, peaking with the peak in rainfall and humidity that concurs with the vegetative stage of the crop. The population of the midge declines as temperatures rise. In conclusion, prediction models may be developed based on weather parameters, to aid in forecasting the field incidence of O. oryzivora and its management strategies. Furthermore, it maybe possible to reduce the damage caused by O. oryzivora to rice crops by altering planting period and taking into account environmental factors.

■Enriched Coal Ash Utilization for Augmenting Production of Rice Under Acid Lateritic Soil

The use of industrial wastes such as fly ash (FA) or rice husk ash (RHA), along with paper factory sludge (PFS), farmyard manure (FYM), and chemical fertilizers (CF), under integrated nutrient management, was studied in acid lateritic soil on rice. Application of combined fertilization sources increased growth, yield attributes, and yield (up to 92.3 and 9.7% over control and CF, respectively) of wet season rice. The uptake of N, P, K, Ca, Mg, Fe, Mn, Zn, Cu, and Co was increased under combined fertilization sources. The study also indicated that such integrated plant nutrition system improved physico-chemical properties of soil with respect to bulk density, pH, electrical conductivity, organic carbon, and available nutrient content. Utilization of these wastes saved chemical fertilizers to the extent of 37.8, 59.7, and 86.5% N, P, and K respectively, with an added advantage of minimizing environmental pollution. f 2010 The University of Kentucky Center for Applied Energy Research and the American Coal Ash Association All rights reserved. A R T I C L E I N F O Article history: Received 15 March 2010; Received in revised form 29 May 2010; Accepted 14 June 2010

Consistency of genotypic performance of lowland rice in wet and dry season in Lao PDR

Lowland rice in Laos as in some other SE Asian countries is grown mostly under rainfed conditions in wet season (WS), but some crops are grown under irrigated conditions in dry season (DS). In Laos, the rice breeding program is concentrating on development of photoperiod insensitive varieties which can be grown in both WS and DS, nevertheless most selection is conducted in WS. In order to determine consistency of genotypic performance between WS and DS, 23 advanced breeding lines and varieties were grown in both seasons for 2–3 years at four locations in the country. All experiments in DS showed significant genotypic variation for grain yield, while genotypic variation was smaller and often not significant in each experiment in WS. The heritability was also higher in DS than in WS. Significant genotype-by-environment interaction was found, and some of this interaction was due to long duration genotypes being affected by extreme temperature conditions in DS particularly at a high altitude location in Northern Laos. Cluster analyses indicate that the genotypic discrimination was large in experiments with intermediate yield levels (mean yield of 2.9–3.8 t/ha). It is concluded that the use of DS trials should be increased to improve the efficiency of selection for widely adapted varieties in the lowland rice breeding program in Laos and other countries of similar growing conditions.

Rice Growth, Grain Yield, and Floodwater Nutrient Dynamics as Affected by Nutrient Placement Method and Rate

The loss of major nutrients can be high in rice (Oryza sativa L.) fields, particularly rainfed rice, where water flowing from field to field during periods of high rainfall not only reduces the nutrient use efficiencies but also has the potential for environmental degradation. We examined the influence of deep point placement of N, P, and K briquettes compared to broadcast incorporation of N, P, and K on floodwater nutrient loads after fertilizer application and on the performance of wet season rice in a Vertisol. Broadcast application of N as urea resulted in an average 10 times higher amounts of ammonium N in floodwater compared to deep placement of urea briquette. The broadcast application of single superphosphate resulted in 67 times higher amounts of P in floodwater than plots receiving deep placed P. The floodwater NH4+–N and P content in the deep placement treatments were negligible—similar to floodwater N and P content without fertilizer application. The floodwater K amounts were also significantly lower with deep placed N–P–K briquettes. Significantly higher grain and straw yields, total N, P, and K uptake, and N and P use efficiencies were observed with deep placement of N–P–K compared to broadcast application of N–P–K. Deep placed N–P briquettes gave significantly higher grain yield, straw biomass, total P and K uptake, apparent P recovery, and agronomic N and P use efficiencies when plant spacing was reduced from 20 by 20 cm to 20 by 10 cm. Closer plant spacing led to better utilization of P and K and provided opportunities for deep placement of N–P or N–P–K briquettes in soils with low available P. Combining site specific characteristics (high soil pH, low percolation rate, high rainfall and surface runoffs) with plant spacing and N–P–K briquettes prepared based on site‐specific nutrient requirements offers potential for higher yields, improved fertilizer use efficiency, balanced fertilization, and reduced nutrient losses.

Impacts of water cycle changes on the rice market in Cambodia: stochastic supply and demand model analysis

A supply and demand model for rice in Cambodia, which includes among other factors evapotranspiration as a water supply variable impacting regional yields and planted areas, is developed to aid in the design of agricultural policies and planning. Impacts are determined stochastically by drawing on water cycle distributions and evaluating the resulting variation in production and price bands for local rice markets. The results of the baseline analyses indicate that production of wet and dry season rice steadily increases and the consumption per capita slightly decreases due to the negative income elasticity. Results of a partial stochastic analyses show that the production of rice in regions where elevations are high and the land vulnerable to flooding are the most sensitive to increased fluctuations in water supply. The changes also affect the rice market through equilibrium price changes. The upper price band, which is the width between average and 90th percentile, is larger than the lower band, which is the width between average and tenth percentile, suggesting that the situation of low income consumers could grow worse under an unstable environment with relatively larger upward price spikes. The results imply that development of irrigation facilities and water management systems maybe required for Cambodian provinces which rely heavily on agriculture, particularly rice production, under increasing climatic variation.

Long‐Term Integrated Nutrient Management for Rice‐Based Cropping Pattern: Effect on Growth, Yield, Nutrient Uptake, Nutrient Balance Sheet, and Soil Fertility

A 7‐year‐long field trial was conducted on integrated nutrient management for a dry season rice (Boro)–green manure (GM)–wet season rice (T. Aman) cropping system at the Bangladesh Rice Research Institute Farm, Gazipur during 1993–1999. Five packages of inorganic fertilizers, cow dung (CD), and GM dhaincha (Sesbania aculeata) were evaluated for immediate and residual effect on crop productivity, nutrient uptake, soil‐nutrient balance sheet, and soil‐fertility status. Plant height, active tiller production, and grain and straw yields were significantly increased as a result of the application of inorganic fertilizer and organic manure. Usually, the soil‐test‐based (STB) fertilizer doses for a high‐yield goal produced the highest grain yield of 6.39 t ha−1 (average of 7 years) in Boro rice. Application of CD at the rate of 5 t ha−1 (oven‐dry basis) once a year at the time of Boro transplanting supplemented 50% of the fertilizer nutrients other than nitrogen (N) in the subsequent crop of the cropping pattern. A positive effect of GM on the yield of T. Aman rice was observed. Following GM, the application of reduced doses of phosphorus (P), potassium (K), sulfur (S), and zinc (Zn) to the second crop (T. Aman) did not reduce yield, indicating the beneficial residual effect of fertilizer applied to the first crop (Boro rice) of the cropping pattern. The comparable yield of T. Aman was also observed with reduced fertilizer dose in CD‐treated plots. The total P, K, and S uptake (kg/ha/yr) in the unfertilized plot under an irrigated rice system gradually decreased over the years. The partial nutrient balance in the unfertilized plot (T1) was negative for all the nutrients. In the fertilized plots, there was an apparent positive balance of P, S, and Zn but a negative balance of N and K. This study showed that the addition of organic manure (CD, dhaincha) gave more positive balances. In the T4c treatment at 0–15 cm, the application of chemical fertilizers along with the organic manures increased soil organic carbon by (C) 0.71%. The highest concentration of total N was observed with T4c followed by T4d and T4b, where CD was applied in Boro season and dhaincha GM was incorporated in T. Aman season. The sixfold increase in soil‐available P in T4b‐, T4c‐, T4a‐treated plots was due to the addition of CD. Dhaincha GM with the combination of chemical fertilizer helps to mobilize soil‐available P by 3 to 6 ppm. The highest amount of soil‐available S was found in T4c‐ and T4a‐treated plots. It was 2.5 times higher than that of the initial soil. The application of CD and dhaincha GM along with chemical fertilizers not only increased organic C, total N, available P, and available S but also increased exchangeable K, available Zn, available iron (Fe), and available manganese (Mn) in soil.

Temporal Origin of Nitrogen in the Grain of Tropical Wet‐Season Rice

The total N in the grain is the integral of the product of the total N absorbed at any instant and the fraction of that N eventually allocated to the grain. We investigated the temporal origin of N in the grain of a wet season rice crop and tested the suitability of 15N nitrate (NH4 15NO3) as a label for that purpose. The total N content of rice (Oryza sativa L.) plants was measured by growth analysis throughout the duration of the crop and the measurements were used to calculate the rate of total N uptake. A point‐placement technique was used to deliver small amounts of 15N nitrate to roots of the rice plant and this enabled the eventual fate of the total N absorbed at any time to be determined. The rate at which N was acquired by the panicle exceeded that by the whole plant at 64 d after transplanting (DAT); thereafter, N was transferred from the leaves to the panicle. About 60% of N in the grain was acquired before panicle initiation and was transferred from leaves during grain filling. A comparison between the uptake and retention of labeled nitrate and urea applied separately at 35 DAT showed that 21 and 58% of the 15N nitrate and 15N urea, respectively, were recovered. There were no advantages of using 15N nitrate as opposed to 15N urea as a label in such research of irrigated rice.

Integrating rice and wheat productivity trends using the SAS mixed-procedure and meta-analysis

Long-term trends of crop yields have been used as a means to evaluate the sustainability of intensive agriculture. Previous studies have measured yield trends from long-term rice–rice and rice–wheat experiments in different sites from the slopes of individual site regressions of yield over time. The statistical significance of each site regression was determined but not that of the aggregate trend, which could give an indication of the magnitude and significance of global yield change. The random regression coefficient analysis (RRCA) and meta-analysis were used in this study to analyze the aggregate yield trend from several long-term experiments (LTE) across the Indo-Gangetic Plains (IGP) and outside the IGP. Both methods show that there has been a significant ( p < 0.05) declining trend in rice yield in rice–wheat LTEs in South Asia including China with the recommended rates of nutrients, but that there has been no significant change in wheat and system (rice + wheat) yields. There was no significant year × region (IGP versus non-IGP) interaction in rice and wheat yields. However, RRCA showed that the average yield trend was significantly negative (−41.0 kg ha −1 yr −1) only in the IGP. In the rice–rice LTEs, there was a significant year × site (IRRI versus non-IRRI sites) interaction during the dry season but not the wet season. Rice yields declined throughout Asia in the wet season. The average system (dry + wet season rice) yield trends were significantly negative in both IRRI and non-IRRI sites (−170.1 and −52.8 kg ha −1 yr −1, respectively) but the magnitude of yield decline was significantly greater in the IRRI sites than in the non-IRRI sites. Rice in the rice–wheat LTEs showed a significantly positive yield trend with the addition of farmyard manure (FYM) but the initial yield was generally lower with FYM than without FYM. After 15 years, yield increase due to FYM was not evident in most of the LTE.

Rice establishment method affects nitrogen use and crop production of rice–legume systems in drought-prone eastern India

The inclusion of grain legumes in rainfed lowland rice farming systems provides an opportunity to increase food production, household income, and human nutrition of impoverished rice farmers in Asia. We examined the effect of rice establishment method on the performance of wet season rice ( Oryza sativa L.) and post-rice crops of either chickpea ( Cicer arietinum L.) or moong [ Vigna radiata (L.) Wilczek] on an Udic Haplustalf in the drought-prone, rainfed lowlands of eastern India. Rice was either direct seeded in lines on moist soil immediately after the onset of wet season rain or transplanted after sufficient rainwater accumulated for soil submergence. Crop establishment method had no effect on rice performance in a season (2001) with normal rainfall. In a drought season (2002), direct seeding resulted in mean rice grain yield of 2.3 t ha −1, whereas the transplanted rice crop failed. The agronomic efficiency of N fertilizer applied to direct-seeded rice was comparable for the 2 years (18 and 24 kg grain per kg N applied). Topsoil inorganic N was markedly higher following chickpea and moong than following a post-rice fallow. Direct-seeded rice had higher yield and accumulation of N following a post-rice legume than following fallow, but transplanted rice derived no such benefit from the legume. Direct-seeded rice was established 1–2 months before transplanted rice, and direct-seeded rice matured before transplanted rice by 8 days in the favorable season and by 26 days in the drought season. The soil nitrate present after legumes and fallow rapidly disappeared, presumably by denitrification, following the onset of rains and soil flooding prior to transplanting. A portion of this accumulated soil nitrate was taken up by the direct-seeded rice before it could be lost. But transplanted rice did not benefit from this inorganic N derived from legumes because virtually all soil nitrate was lost before transplanting. Direct seeding of rice ensured better use of residual and applied N, reduced risk due to drought, and favored intensification with post-rice legumes in drought-prone lowland systems.

Genotypic Differences in Nitrogen Uptake and Utilization of Wet and Dry Season Rice as Influenced by Nitrogen Rate and Application Schedule

Genotypic Differences in Nitrogen Uptake and Utilization of Wet and Dry Season Rice as Influenced by Nitrogen Rate and Application Schedule

Long-term effects of inorganic and organic fertilizer sources on yield and nutrient accumulation of lowland rice

Deceleration in rice ( Oryza sativa L.) yield over time under fixed management conditions is a concern for countries like Bangladesh, where rice is the primary source of calories for the human population. Field experiments were conducted from 1990 to 1999 on a Chhiata clay loam soil (Hyperthermic Vertic Endoaquept) in Bangladesh, to determine the effect of different doses of chemical fertilizers alone or in combination with cow dung (CD) and rice husk ash (ash) on yield of lowland rice. Two rice crops—dry season rice (December–May) and wet season rice (July–November) were grown in each year. Six treatments—absolute control (T 1), one-third of recommended fertilizer doses (T 2), two-thirds of recommended fertilizer doses (T 3), full doses of recommended fertilizers (T 4), T 2+5 t CD and 2.5 t ash ha −1 (T 5) and T 3+5 t CD and 2.5 t ash ha −1 (T 6) were compared. The CD and ash were applied on dry season rice only. The 10-year mean grain yield of rice with T 1 was 5.33 t ha −1 per year, while the yield with T 2 was 6.86 t ha −1 per year. Increased fertilizer doses with T 3 increased the grain yield to 8.07 t ha −1 per year, while the application of recommended chemical fertilizer doses (T 4) gave 8.87 t ha −1 per year. The application of CD and ash (T 5 and T 6) increased rice yield by about 1 t ha −1 per year over that obtained with chemical fertilizer alone (T 2 and T 3, respectively). Over 10 years, the grain yield trend with the control plots was negative, but not significantly, both in the dry and wet seasons. Under T 3 through T 6, the yield trend was significantly positive in the dry season, but no significant trend was observed in the wet season. The treatments, which showed positive yield trend, also showed positive total P uptake trend. Positive yield trends were attributed to the increasing P supplying power of the soil.

Effect of rice straw management on nitrogen balance and residual effect of urea-N in an annual lowland rice cropping sequence

Two field experiments were conducted in 1999 (wet season) and 2000 (dry season) on a Ustic Endoaquerts in central Thailand to examine the impact of rice straw management practices on rice yield, N uptake and fertilizer-N use efficiency. Treatments included a combination of urea broadcast at a rate of 70 kg N ha−1 with either straw or compost which were incorporated at a rate of 5 Mg ha−1. At maturity of the wet season rice, 15N recovery by the grain was low (11–14%) as well as straw-N derived from labeled N (5–7%). After harvest, 25–29% of applied N still remained in the soil, mainly in the 0 to 5-cm layer. Large amounts of fertilizer-N (53–55%) were lost (unaccounted for) from the soil/plant system during the first crop. Residual fertilizer-N recovery in the second rice crop was less than 3% from the original application. During both fallow seasons NO3−-N remained the dominant form of mineral N (NO3− + NH4+) in the soil but its concentration was low. In the wet season grain yield response to N application was significant (P =0.05). Organic material sources did not significantly change grain yield and N accumulation in rice. In terms of grain yield and N uptake at maturity, there was no significant residual effect of fertilizer-N on the subsequent rice crop. These results indicated that the combined use of organic residues with urea did not decrease total N losses or increase crop yield or uptake of N compared to urea alone.

Nitrate pollution in groundwater and strategies to reduce pollution

The input-intensive rainfed tropical ecosystem, where wet season (WS) rice (Oriza sativa L.)-dry season (DS) diversified high-value upland crops like vegetables predominate, has resulted in a problem of a large leakage of N into the environment, thereby polluting the water. Excessive use of N fertilizer in high-value crops grown in DS is economically motivated. Out of twenty water sources evaluated in a watershed with a total area of 265 ha located in Magnuang, Ilocos Norte, Philippines, twelve had near or above the World Health Organization's (WHO) NO3-N limit for drinking water of 10 ppm. Soil mineral N (upper 100 cm) observed in seven rice-sweet pepper (Capsicum annuum L.) farmers' fields ranged from 111 to 694 kg ha(-1) which decreased by 10 to 68% in plots with dry-to-wet (DTW) crops like indigo, indigo+mungo and corn. In fallow plots where mineral N was either maintained or increased, it showed movement to lower soil profiles demonstrating NO3 leaching without a crop. On average, maize (Zea mays L.) captured 176 kg N ha(-1) and indigo (Indigofera tinctoria L.) 194 kg N ha(-1). In both fallow and planted plots, mineral N declined to low levels at 100% water-filled pore spaces (WFPS) before rice transplanting. A strategy for including indigo plus maize as a N-catch crop is proposed to decrease NO3 leaching and maximize N use efficiency in a rice-sweet pepper cropping system.

Application des indicateurs “approvisionnement relatif en eau” et “productivité de l'eau” à l'analyse des performances des petits périmètres irrigués au Burkina Faso

AbstractThe performance of three small irrigation systems located in the central and the centre eastern regions of Burkina Faso has been analysed at the field level, using two performance indicators: Relative water supply (RWS) to assess the adequacy of “irrigation supply and effective rainfall” and the crop water requirement; Water productivity (Pe) to assess water use efficiency. The results show that the average value of RWS of wet‐season rice fields is very high (1.3) at Gorgo, medium (1.04) at Mogtedo and very low (0.75) at Itenga. The average value of water productivity is high (0.88 kg m−3) at Itenga, medium (0.65 kg m−3) at Mogtedo and low (0.34 kg m−3) at Gorgo.The relationship of RWS to water productivity shows that it would be possible to save irrigation water without decreasing rice yields significantly. However, no significant correlation has been found between the RWS values and the yield values. Copyright © 2001 John Wiley &amp; Sons, Ltd.

Effect of soil enrichment in conjunction with organics and chemical fertilizer on rice (Oryza sativa)-chickpea (Cicer arietinum) cropping system

A field experiment was undertaken at Raipur (M.P.) during wet and dry seasons of 1993-94 and 1994-95 to study the direct effect of urea-N with or without organic materials (paddy straw, farmyard manure and green manure) on productivity of rice (Oryza sativa L.) and its residual effect on yield of chickpea (Cicer ari~tinum L.) grown after rice under rainfed low land vertisol. Application of fertilized green manure as Sesbania rostrata proved superior as compared to paddy straw and farmyard manure. Rice yield and N-uptake were significantly higher under combined application of green manure and urea on an equivalent N basis. Thus, urea-N can be substituted up to 50% by applying Sesbania rostrata . in rice. Residual fert~lity in terms of organic carbon was pronounced under ;s farmyard manure and paddy straw which reflected in terms of higher grain yield of chickpea grown after harvest of wet season rice. Direct application of N up to the recommended level (20 kg Nlha) increased the grain yield of chickpea considerably. However, N-use efficiency decreased with the increasing levels of N from 0 to 20 kg Nltia.

Effect of mixing black clay soil and organic amendment on properties of coarse-textured soil and rice yield

In Tamil Nadu, rice is grown on coarse-textured soils across a significant area with marginal yields. To improve soil, water, and nutrient retention and to enhance rice yields, a field experiment was conducted during the wet seasons of 1996-97 and 1997-98 (October-January), with each season trial done in one of two adjacent fields. Treatments used were different incorporation levels of black clay soil (0, 20, 40, 60, 80, and 100 t ha -1 ), with or without 25 t raw coir pith ha -1 , replicated thrice in a randomized block design. The black clay soil and coir pith were mixed with the puddled soil up to 20 cm depth by trampling and leveling before transplanting. At the beginning of the experiment, soil in control plots had comparable properties such as contents of clay, silt, organic carbon, total N, P, K, Ca, and Mg, available N, P, K, and exchangeable Ca and Mg, electrical conductivity (EC), pH, and cation exchange capacity (CEC) as the soil in the rest of the field. Rice varieties IR60 and ADT36 (parentage: local variety, Triveni/ IR20) were grown in the first and second croppings, respectively. Grain and straw yield were recorded. Neither field supported any crop other than the wet-season rice crop under study. The soil was coarse-textured throughout the solum of 2 m and was classified as a coarse loamy, kaolinitic, nonacid, isomegathermic Typic Ustipsamment.