Rainfed Rice Production Research Articles

Farmers’ knowledge, use and preferences of parasitic weed management strategies in rain-fed rice production systems

Rain-fed rice production in sub-Saharan Africa is often hampered by parasitic weeds. This study assessed farmers’ awareness, use, preference and adoption criteria of parasitic weed management practices in rain-fed rice production environments in Tanzania. Surveys and workshops were organized in three affected rice growing areas in Morogoro-rural, Songea and Kyela district, supplemented with on-farm experiments in Kyela. In all districts, farmers were aware of the locally occurring parasitic weed species, Rhamphicarpa fistulosa (lowland) and Striga asiatica (upland), and they considered these weeds more problematic than non-parasitic weeds. Though they mostly practise hand weeding, farmers were aware of a wide range of control options. Local access, affordability, ease of implementation and control efficacy were considered important criteria for adoption, whereas trade-offs, like lack of preferred grain quality traits in resistant varieties, were mentioned as an important break on adoption. Based on informal discussions with farmers, altered sowing times, resistant rice varieties and soil amendments were marked as feasible control options and tested in a farmer-participatory manner in four years of experimentation in upland and lowland fields. In both types of fields, the contribution of soil amendment to parasitic weed suppression was not evident, but rice husk was marked as a suitable and cheap alternative to inorganic fertilizers. Control of R. fistulosa in lowlands was perceived to be best realized by early crop establishment, escaping major parasite damage due to the relatively slow early development of this weed species. The local variety Supa India, appreciated for its grain qualities and marketability, remained the preferred variety. For the control of S. asiatica, late planting was preferred, requiring a short-duration variety to minimize risk of drought stress during grain filling. The short-duration NERICA-10 was most preferred, as it combined a favourable short cycle length with resistance to S. asiatica and good grain appearance. Farmer participation in technology testing showed to be crucial in defining locally adapted and acceptable parasitic weed control strategies. Yet, it is argued that without lifting important constraints related to credit and input supply, it will be impossible to sustainably solve the parasitic weed problem in rain-fed rice.

DETERMINANTS OF YIELD GAP IN RAINFED AND IRRIGATED RICE PRODUCTION SYSTEMS – EVIDENCE FROM HOUSEHOLD SURVEY IN KWARA STATE, NIGERIA

The actual yield of rice in Nigeria has not been able to reach its potential. Consequently, the cost of rice importation is alarming. However, rice yield varies under various production systems. Therefore, this study examines the determinants of yield gap in rainfed and irrigated rice production systems in Kwara state, Nigeria. Gross Margin Budgetary analysis, Stochastic Frontier, and Linear Regression Model were respectively used to estimate the profitability, technical efficiency, and determinants of yield gap in both production systems. The result shows that rice production is more profitable and efficient under the irrigated rice production system than the rainfed rice production system. It was also discovered that the significant determinants of yield gap in both production systems vary. However, the size of farm cultivated and the rice variety planted are common significant determinants of yield gap in both systems. This research therefore recommends that irrigation facilities and improved rice variety should be made available to farmers. Additionally, policy makers should formulate policies that would enable rice farmers to have access to larger farm lands. (original abstract)

Parasitic weed incidence and related economic losses in rice in Africa

Parasitic weeds pose increasing threats to rain-fed rice production in Africa. Most important species are Striga asiatica, S. aspera and S. hermonthica in rain-fed uplands, and Rhamphicarpa fistulosa in rain-fed lowlands. Information on the regional spread and economic importance of parasitic weeds in cereal production systems is scant. This article presents the first multi-species, multi-country, single-crop impact assessment of parasitic weeds in Africa. A systematic search of public international and national herbaria and the scientific literature was conducted to collect all available data on the regional distribution, incidences and related yield losses of the most important parasitic weeds in rice. Herbaria specimens were geo-referenced and these coordinates were overlapped with rain-fed rice areas. Probabilistic diffusion waves of parasitic weeds were generated to derive most likely incidence values. Estimates from this spatial analysis were then combined with secondary data from the literature into a stochastic impact assessment model to generate a confidence interval of the likely economic impact per country and for sub-Saharan Africa as a whole. Rhamphicarpa fistulosa occurs in at least 36 African countries, 28 of which produce rice in rain-fed lowlands where this species thrives. Striga hermonthica is found in at least 32 countries, Striga asiatica in at least 44 and S. aspera in at least 17. A total of 50 countries have at least one of these three species of Striga, 31 of which produce rice in the rain-fed uplands where these species can be encountered. An estimated 1.34 million ha of rain-fed rice is infested with at least one species of a parasitic weed in Africa. Our stochastic model estimates that annual economic losses inflicted by all parasitic weeds exceeds, with 95% certainty, a minimum value of US $111 million and most likely reaches roughly US $200 million and increases by US $30 million annually. To reverse this trend and support small-holder rice farmers in Africa with effective, sustainable and affordable solutions for control, targeted investments in research, development and capacity building are required. The top-10 priority countries where such investments would probably have the highest return are Nigeria, Guinea, Mali, Côte d’Ivoire, Cameroon, Tanzania, Madagascar, Uganda, Sierra Leone and Burkina Faso.

Teleconnections of ENSO and IOD to summer monsoon and rice production potential of India

Regional trend of summer monsoon precipitation has been analyzed for broad physical regions of India namely, (i) Indo-Gangetic plain, (ii) Central and East India, (iii) Coastal and Peninsular India and (iv) Western India. A significantly drying trend has been found in the two regions namely, Indo-Gangetic plain and Central and East India with comparative seasonal rate of drying higher in the latter region. A complex relation between the regional trend of summer monsoon precipitation, global teleconnection parameters and rice production of the regions have been studied. El Niño-Southern Oscillation (ENSO) and Indian Ocean dipole (IOD) have a significant role in the precipitation anomaly of Indo-Gangetic plain unlike Central and East India where the ENSO only plays role as global teleconnection parameter. Rice production of Central and East India has been found to be affected adversely during the El Nino years. Central and East India is found to be the worst affected region compared to the Indo-Gangetic plain with respect to its fragile rainfed rice production potential and strong adverse teleconnection of El Nino on the rice production in this zone.

Canopy scale CO2 exchange and productivity of transplanted paddy and direct seeded rainfed rice production systems in S. Korea

Rice (Oryza sativa L.) is a primary food crop that supports more than half the world population. Paddy rice accounts for more than 75% of the total global rice production but requires large amounts of water for irrigation. Increasing water scarcity, however, raises concerns regarding the sustainability of paddy rice production and highlights the need for alternative approaches. Improved rice varieties that require less water, are drought tolerant and which can be directly seeded offer promising alternatives. In this study, we evaluated the performance of an improved rice variety (Oryza sativa subsp. Japonica cv. Unkwang) grown under direct seeding and rainfed cultivation. Aboveground biomass and leaf area development were measured every month by destructive harvesting. Canopy net ecosystem CO2 exchange (NEE) and ecosystem respiration (Reco) were measured using chambers. Gross primary production (GPP) was calculated from NEE and Reco. The maximum green leaf area index (GLAI) attained under rainfed agriculture was 4.9±0.5m2m−2 compared to 5.4±1.1m2m−2 in the conventional paddy rice production system. The respective peak total aboveground biomasses were 2.16±0.28 and 1.85±0.27kgm−2 while the corresponding grain weights were 1.19±0.10kgm−2 and 1.16±0.09, amounting to total yields of 6.61±0.22 and 5.99±0.68t/ha−1 for paddy and rainfed rice, respectively. The maximum daily cumulative GPP were 11.1 and 12.0gCm−2d−1, respectively, occurring at peak season, corresponding to maximum photosynthetic active radiation (PAR) and GLAI. On a daily basis, PAR explained >82% of the daily fluctuations in GPP while >90% of the seasonal changes in GPP were due to changes in GLAI and light use efficiency (α). Higher α in rainfed rice was attributed to higher leaf nitrogen (N) content. With adequate soil moisture supply, the Unkwang variety demonstrated the potential to grow under rainfed agriculture with comparatively good amount of yield. Since direct seeding, as in rainfed agriculture, eliminates the need for prior flooding of plots, it maximizes the use of early rainfall, which could be a water saving strategy and a reason to promote the introduction of Unkwang variety in the paddy rice-dominated Asian farming system.

Rice yields under Rhamphicarpa fistulosa-infested field conditions, and variety selection criteria for resistance and tolerance

The facultative parasitic weed Rhamphicarpa fistulosa, is a widespread problem in rain-fed rice production systems in Africa. Little is known about rice varietal differences in infection level and yields in fields infested by this root hemi-parasite. During three cropping seasons (2012–2014), an experiment was conducted to address these knowledge gaps and to identify suitable variety selection criteria for R. fistulosa resistance and tolerance. Sixty-four adapted lowland rice varieties, including all interspecific lowland varieties of NERICAs, their most common parents – IR64 and TOG5681 – and two locally popular varieties – Mwangulu and Supa India – were grown in an R. fistulosa-infested field in southern Tanzania. As expected from a facultative parasite, host plant varieties had no effect on R. fistulosa numbers. Consistent varietal differences in R. fistulosa biomass were however observed, with no Year×Variety effects, and this parameter can therefore be used to select for resistance. Parasite-free observation plots were established in the last year. Due to the facultative nature of the parasite, creating such R. fistulosa-free plots was simply obtained by regular early weeding. The presence of parasite-free control plots enabled assessment of worthwhile additional information such as parasite-free yield, parasite-inflicted yield losses (RYLR) and varietal differences in tolerance. Under R. fistulosa-infested conditions (3-season averages, no Year×Variety interaction effect), rice grain yields ranged from 1.2tha−1 for the worst performing variety (TOG5681) to 2.4tha−1 for the best performing varieties (NERICA-L-39, -20). Under R. fistulosa-free conditions (2014 only) rice grain yields ranged from 2.4 (NERICA-L-22) to 5.4tha−1 (NERICA-L-17). Tolerant varieties were characterized by a low RYLR and a high parasite biomass (e.g. Supa India, NERICA-L-20). The selection measures identified are effective, easy and practical under field conditions. They facilitated identification of thirteen varieties with high resistance, sixteen varieties with low RYLR and two varieties with high tolerance. These varieties would be invaluable for future rice breeding programs. For farmers in R. fistulosa-endemic areas the most promising varieties are probably NERICA-L-40 and -31, as they combine good yields under infested conditions with low levels of parasite infection.

Socioeconomic Determinants of Rain-fed Rice Production among Small-scale Farmers in the Shama-Ahanta East District of Ghana

Socioeconomic Determinants of Rain-fed Rice Production among Small-scale Farmers in the Shama-Ahanta East District of Ghana

Drought stress impacts of climate change on rainfed rice in South Asia

Rice production is threatened by climate change and the productivity of rainfed rice is increasingly challenged. A better understanding of the future trends of rice production associated with climate change is important for improving food security. Rice production under irrigated and rainfed conditions was simulated using the rice crop model ORYZA2000. Simulated rice yield representing crop and environment interaction was used to evaluate the drought impact of climate change on rainfed rice in South Asia. If rainfed rice system was applied in all current rice cultivating areas in South Asia, drought stress could result to yield losses of more than 80 in 22 %, but crop failure was lower than 40 in 73 % of the areas under mild and severe SRES A1B and A2. The spatial patterns of drought stress on rainfed rice were similar under both A1B and A2, and the yield loss and crop failure decreased slightly in the far future (2045 to 2074) in areas where drought risk was high in the near future (2015 to 2044), but the impacts would gradually increase over initially low-impact areas. Both A1B and A2 would shift the best sowing season of rainfed rice to be earlier or later by up to 90 days in 30 years. Appropriate adjustment of sowing season is a major adaptation strategy for rainfed rice production in South Asia to benefit from climate change. In this case, rainfed rice yield could potentially increase by about 10 % in most areas of South Asia associated with 10 to 50 % lower inter-annual variation and slightly higher risk for crop failure.

Fine mapping of consistent quantitative trait loci for yield under drought stress using rice (Oryza sativa) recombinant inbred lines adapted to rainfed environment

Drought stress is a serious constraint, especially in rainfed rice production, and breeding for drought tolerance by selection based on yield under stress, though effective, is slow Mapping quantitative trait loci (QTLs) for yield and its components under drought stress predominant in rainfed target populations of environment (TPE) will help overcome this limitation. In the present study, a subset of 143 F8 and F9 recombinant inbred (RI) lines derived from IR62266-42-6-2 (IR62266), a high-yielding indica ecotype and Norungan, a landrace from TPE, was used to map QTLs for yield and its components under drought predominant in TPE. A large effect yield QTL observed under drought stress in TPE was consistent across two years with a phenotypic variation of 31.3% and 37.9% and additive effect of 629.2 and 424.9 kg/ha Further, this region was fine-mapped to 94.0 kb with positive effect on grain yield under stress.

Mapping Consistent Rice (Oryza sativa L.) Yield QTLs under Drought Stress in Target Rainfed Environments.

BackgroundDrought stress is a major limitation to rainfed rice production and yield stability. Identifying yield-associated quantitative trait loci (QTLs) that are consistent under drought stress predominant in target production environments, as well as across different genetic backgrounds, will help to develop high-yielding rice cultivars suitable for water-limited environments through marker-assisted breeding (MAB). Considerable progress has been made in mapping QTLs for drought resistance traits in rice; however, few have been successfully used in MAB.ResultsRecombinant inbred lines of IR20 × Nootripathu, two indica cultivars adapted to rainfed target populations of environments (TPEs), were evaluated in one and two seasons under managed stress and in a rainfed target drought stress environment, respectively. In the managed stress environment, the severity of the stress meant that measurements could be made only on secondary traits and biomass. In the target environment, the lines experienced varying timings, durations, and intensities of drought stress. The rice recombinant inbred lines exhibited significant genotypic variation for physio-morphological, phenological, and plant production traits under drought. Nine and 24 QTLs for physio-morphological and plant production traits were identified in managed and natural drought stress conditions in the TPEs, respectively. Yield QTLs that were consistent in the target environment over seasons were identified on chromosomes 1, 4, and 6, which could stabilize the productivity in high-yielding rice lines in a water-limited rainfed ecosystem. These yield QTLs also govern highly heritable key secondary traits, such as leaf drying, canopy temperature, panicle harvest index and harvest index.ConclusionThree QTL regions on chromosome 1 (RM8085), chromosome 4 (I12S), and chromosome 6 (RM6836) harbor significant additive QTLs for various physiological and yield traits under drought stress. The similar chromosomal region on 4 and 6 were found to harbor QTLs for canopy temperature and leaf drying under drought stress conditions. Thus, the identified large effect yield QTLs could be introgressed to develop rice lines with stable yields under varying natural drought stress predominant in TPEs.Electronic supplementary materialThe online version of this article (doi:10.1186/s12284-015-0053-6) contains supplementary material, which is available to authorized users.

Energy balance and energy economic analyses of rice production systems in Ayeyarwaddy Region of Myanmar

The status of energy balance and energy economics of irrigated and rain-fed rice production systems is studied and compared for highlighting the effect of farm size. Primary data were collected from 51 irrigated and 54 rain-fed rice farms in Northern Ayeyarwaddy Region, Myanmar. Farm classes were identified as small (<2.5 ha) and large (2.5–25 ha). Energy estimates were calculated from actual amount of inputs and outputs and corresponding conversion factors. Results showed that the total energy inputs were 19,170.5 and 11,031.1 MJ/ha, respectively, in irrigated and rain-fed rice systems, while the total energy outputs were 104,162.7 and 65,033.5 MJ/ha in the two systems, respectively. Energy efficiency ratios, defined as output-to-input energy values, were 5.6 and 5.9 in irrigated and rain-fed rice production systems. Interestingly, the two systems were not statistically different for their energy efficiencies. Similarly, the energy efficiency ratios for different farm classes under both rice production systems were also not statistically different. Energy productivity and specific energy were 0.27 and 3.8 kg/MJ; 0.29 and 3.9 MJ/kg in irrigated and rain-fed systems, respectively. The energy benefit–cost ratio was higher in rain-fed rice (1.1) than in irrigated rice (0.9) system. Rain-fed system seems to have potential of further increasing yield through the increased yet appropriate use of energy inputs.

Analysis of rainfall for rainfed rice production in Chhattisgarh state

Analysis of rainfall for rainfed rice production in Chhattisgarh state

Analysis of Rainfall Probabilities for Strategic Crop Planning in Raipur District of Chhattisgarh State

Rainfall data of recent forty three years (1971-2013) of Labhandi station, Indira Gandhi Krishi Vishwavidhyalaya Raipur, Chhattisgarh was analysed with the method of incomplete gamma probability. The data revealed that the average rainfall of labhandi station is 1202 mm spread over 61 rainy days. Out of this 1055, 68, 53 and 27 mm received from south west monsoon (June-September), north east (October-December), summer (March-May) and winter season (January -February) respectively. Probability for receiving more than 100 mm of rainfall can be expected only at 25% probability level and that too in four weeks which is leading to the interpretation that rainfed rice production is a challenging task in this region. it has been found that at 75 per cent assured probability level rainfall of more than 200 mms can be expected only in July and August months and this rainfall is hardly sufficient for meeting the water requirement in upland situations. However at 50 per cent probability which is equivalent to average condition, cultivation of rice is possible under well water management conditions. On seasonal basis rainfall at assured probability level of 75% is not sufficient as the quantity is 795 mm rainfall in south-western monsoon season.

Monsoon variability, crop water requirement, and crop planning for kharif rice in Sagar Island, India.

In the Sagar Island of Bay of Bengal, rainfed lowland rice is the major crop, grown solely depending on erratic distribution of southwest monsoon (SM) rainfall. Lack of information on SM rainfall variability and absence of crop scheduling accordingly results in frequent occurrence of intermittent water stress and occasional crop failure. In the present study, we analyzed long period (1982-2010) SM rainfall behavior (onset, withdrawal, rainfall and wetness indices, dry and wet spells), crop water requirement (CWR, by Food and Agriculture Organization (FAO) 56), and probability of weekly rainfall occurrence (by two-parameter gamma distribution) to assess the variability and impact on water availability, CWR, and rice productivity. Finally, crop planning was suggested to overcome monsoon uncertainties on water availability and rice productivity. Study revealed that the normal onset and withdrawal weeks for SM rainfall were 22nd ± 1 and 43rd ± 2 meteorological weeks (MW), respectively. However, effective monsoon rainfall started at 24th MW (rainfall 92.7 mm, p > 56.7 % for 50 mm rainfall) and was terminated by the end of 40th MW (rainfall 90.7 mm, p < 59.6 % for 50 mm rainfall). During crop growth periods (seed to seed, 21st to 45th MW), the island received an average weekly rainfall of 65.1 ± 25.9 mm, while the corresponding weekly CWR was 47.8 ± 5.4 mm. Despite net water surplus of 353.9 mm during crop growth periods, there was a deficit of 159.5 mm water during MW of 18-23 (seedling raising) and MW of 41-45 (flowering to maturity stages). Water stress was observed in early lag vegetative stage of crop growth (32nd MW). The total dry spell frequency during panicle initiation and heading stage was computed as 40 of which 6 dry spells were >7 days in duration and reflected a significant (p < 0.05) increasing trend (at 0.22 days year(-1)) over the years (1982-2010). The present study highlights the adaptive capacity of crop planning including abiotic stress-tolerant cultivars to monsoon rainfall variability for sustaining rainfed rice production vis-à-vis food and livelihood security in vulnerable islands of coastal ecosystem.

Quantifying production losses due to drought and submergence of rainfed rice at the household level using remotely sensed MODIS data

Combining remotely sensed Moderate Resolution Imaging Spectroradiometer (MODIS) data with Bangladesh Household Income and Expenditure Survey (HIES) data, this study estimates losses in rainfed rice production at the household level. In particular, we estimated the rice areas affected by drought and submergence from remotely sensed MODIS data and rice production from Household Income and Expenditure Survey (HIES) data for 2000, 2005 and 2010. Applying two limit Tobit estimation method, this study demonstrated that both drought and submergence significantly affected rice production. Findings reveal that on average, a one percent increase in drought affected area at district level reduces Aman season rice production by approximately 1382 kilograms per household on average, annually. Similarly, a one percent increase in drought area reduces rainfed Aus season rice production by approximately 693 kilograms per household, on average, annually. Based on the findings the paper suggests disseminating and developing drought and submergence tolerant rice and also short duration rice varieties to minimize loss caused by drought and submergence in Aus and Aman rice seasons.

A decision-making model for rice paddy cropping in an urbanizing area of the Lao PDR

In Southeast Asia, economic and population growth are expected in the near future. Rapid change is anticipated especially in the Lao PDR. Concern has been expressed that population growth will lead to an increased demand for food and economic growth to changes in the use of land. For food production to keep pace with the growth of population, it is very important to understand decision-making in rice paddy cultivation in urbanizing areas; for this reason, this study with the SEM model was conducted. The original data were collected by a questionnaire survey in some Lao villages; the survey included questions on various conditions, such as the availability of water in the dry season (irrigation), the access to a city, and job opportunities other than farming. The findings of the study demonstrate that the planting of a second rice crop was related to such factors as the productivity of rain-fed rice and cash crops and, most importantly, job opportunities other than farming.

RAAIS: Rapid Appraisal of Agricultural Innovation Systems (Part II). Integrated analysis of parasitic weed problems in rice in Tanzania

Parasitic weeds such as Striga spp and Rhamphicarpa fistulosa in smallholder rice production systems form an increasing problem for food and income security in sub-Saharan Africa. In this paper we implement the Rapid Appraisal of Agricultural Innovation Systems (RAAIS) as a diagnostic tool to identify specific and generic entry points for innovations to address parasitic weeds in rain-fed rice production in Tanzania. Data were gathered across three study sites in Tanzania where parasitic weeds are eminent (Kyela, Songea Rural and Morogoro Rural districts). The results demonstrate that in Tanzania, weeds in general and parasitic weeds in particular receive little attention in agricultural research, training and education curricula. Crop protection policies mainly focus on the control of (insect) pest and diseases and there is relatively little attention for weed prevention, which is essential for addressing parasitic weed problems effectively. Specific entry points for innovation include increasing awareness of parasitic weed problems among farmers, extension and crop protection officers and policymakers. In regions where awareness is relatively high, participatory research approaches can provide a basis for developing locally adapted parasitic weed management strategies. Generic entry points for innovation include enhanced collaboration and interaction between stakeholders across different levels, for example in multi-stakeholder platforms. This can provide the basis for developing and implementing coherent policy and development strategies to address structural constraints in the agricultural system, including the promotion of clean local seed systems, investments in physical and knowledge infrastructure development, adequate backstopping of agricultural extension officers, agribusiness training for farmers, quality control of agricultural inputs, timely access to agricultural inputs, and improved access to markets for farmers. Together the specific and generic entry points can strengthen the innovation capacity of Tanzania's agricultural system to address parasitic weed problems, as well as other complex agricultural problems.

Rainfall Variability in Chhattisgarh State Using GIS

Chhattisgarh state located in central India covers total area of about 13.5 million hectares. The region has a great variety and diversity of weather conditions. Three major agro-climatic zones has been demarcated in the state viz., Chhattisgarh plains zone, Bastar plateau ACZ and Northern hill region. Here an analysis of rainfall for 16 districts has been made and interpretation drawn regarding pre-dominant crop rice cultivation. Further stress has been made to conserve surplus monsoonal rainfall in On Farm Reservoirs (OFR’s) as rainfall is occurring in intense storms and utilize this rainwater for sustainable crop production and also for enhancing cropping intensity. The high potential of OFR’s and other harvesting structures in alleviating drought, increasing productivity and stability of rainfed ricelands has been tested in this region for meeting this challenge of rainfed rice production.

Determinants of parasitic weed infestation in rainfed lowland rice in Benin

The parasitic weed Rhamphicarpa fistulosa is threatening rainfed lowland rice production in Benin. The aim of this study was to explore factors (such as biophysical characters of the rice growing environment, farmers’ management practices, and socioeconomic characteristics) that affect the infestation of rainfed lowland rice fields by R. fistulosa and farmers’ ability to cope with the problem. Data were collected from 231 rice plots located in 12 inland valleys infested by Rhamphicarpa in Benin. Data were analyzed using a double hurdle model, which analyses both the likelihood (of occurrence) and the severity of infestation. Results showed that 72% of the surveyed rice plots were infested by R. fistulosa and the average severity was 109 plants m−2. The likelihood of infestation was higher on poorly fertile soils and fields located in the inland-valley bottom, and it decreases through timely use of herbicides and ploughing. Severity of infestation was higher on rice plots cultivated by female-headed households farmers and reduced through management practices such as late sowing, timely application of post-emergence herbicide, three hoe or hand weeding operations, medium-rate fertilizer application and prolonged fallow. Likelihood and severity of infestation were found to be negatively correlated. These findings suggest that farmers can reduce the likelihood and the severity of infestation of their plot as long as they are aware of factors causing the problem given their access to and management capacity of production resources.

Incidence of drought in relation to rainfed rice production: An analysis

The distribution of rainfall during a season is more important than its amount. It is therefore, the progressive balance between the receipt and expenditure of the moisture during the growing season, which creates favourable or unfavourable conditions for successful crop production. Several research workers have attempted to study the various aspects of drought on this basis. Their studies have not taken into account the crop yields in determining the agricultural drought. In this paper, the data on rainfall (1945 to 1993) and yield of a crop like rainfed rice in Midnapore district of West Bengal (India) have been analyzed for determining drought threshold value and characterizing agricultural drought. An amount of 20 mm rainfall for two consecutive weeks was identified as drought threshold value in the test location. During drought period, high negative correlation between grain yield and maximum rainfall was observed. The recurrence of drought in relation to rainfed rice has also been studied.