Rainfed Ecosystem Research Articles

Development of Guava + Pineapple Two Tier Cropping System under Rain-Fed Ecosystem of Jharkhand Province of India

Development of Guava + Pineapple Two Tier Cropping System under Rain-Fed Ecosystem of Jharkhand Province of India

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.

Can models help to forecast rainwater dynamics for rainfed ecosystem?

Simulation models are important tools to explore and illustrate dynamics of climatic variables in crop based ecosystem. In the rainfed ecosystem (RE), wheat production is impinged on certain climatic events per se high variability in rainfall and increased temperature. These climatic events turn out due to climatic drivers like Sea Surface Temperatures (SSTs) and pressure. Current study is aimed to analyze long term rainfall data (1961–2011) of Pakistan׳s rainfed ecosystem zone (Islamabad, Chakwal and Talagang) by using Agricultural Production Systems Simulator (APSIM) and R model. The principal objective of this analysis was to study the link between SOI phases and SSTs; and thereby understanding the pattern of climate change due to these climatic drivers under rainfed conditions in Pakistan. The results revealed a positive link between July SOI phases and the rainfall variability during October–November (the sowing time of wheat in Pakistan). Long term rainfall data analysis (1961–2011) of Islamabad, Chakwal and Talagang revealed 44%, 40%, 35% possibility of exceeding median rainfall near zero whereas probability of consistently negative SOI phases were 35%, 34% and 33% respectively during July. Similarly, the forecasting results estimated by R using covariates like dry spell, NINO1.2, NINO3, NINO4, NINO3.4 and IOD of different months revealed that prediction of monsoon, wheat early growth, wheat grain filling period and total wheat growing season rainfall, have significant signals with climatic drivers. The study justified the importance of models in the decision making processes and rainfall forecasting as a beneficial and necessary tool for rainfed ecosystem conservation.

Ridge-furrow with full plastic film mulching improves water use efficiency and tuber yields of potato in a semiarid rainfed ecosystem

A planting pattern of alternate ridges and furrows with plastic film mulching has been viewed as a best management practice for crop production in the arid and semiarid regions, but there is a lack of insight into the underlying changes in soil–crop water relations on mulching areas and ridge-furrow shapes for potato (Solanum tuberosum L.) production. A field study with comparisons of three mulching areas and two ridge-furrow shapes was conducted for two years (2009 and 2010) to assess evapotranspiration, water use efficiency, and tuber yields in the semiarid Northwest China. The experiment included five mulching area and ridge-furrow shape combinations: (1) full mulching on double ridges and furrows (DRFFM), (2) full mulching on both ridges and furrows (RFFM), (3) half mulching only on ridges (RFHM), (4) no mulching on ridges and furrows (RFNM), and (5) traditional-flat planting and without mulching as the control (CK). The two full mulching treatments had the best effect on topsoil temperature–moisture, improved emergence rate by 9.3–14.4% and advanced emergence by 8.1–11.7 days (P<0.05). Full mulching treatments reduced evapotranspiration by about 24.0–45.0% during emergence, but increased it by up to 18.7% thereafter, primarily due to rapid increase of LAI under faster development, and also enhanced root/shoot ratio (P<0.05). Full mulching produced the highest tuber yields (57.4–78.2% higher than the CK) with higher cost of mulching material and labour than the half or no mulching treatments. The full mulching also resulted in the highest water use efficiency (increased by 56.8–70.3% than the CK). The beneficiary effects became smaller with the decrease of mulching areas. However, the difference between the two full mulching treatments was not significant (P>0.05) despite there was slightly higher WUE in DRFFM than RFFM. Our results revealed that the full mulching on ridge-furrow planting strategy was effective to increase potato productivity and water use efficiency in the semiarid area of Chinese Loess Plateau.

Effects of Stocking Density on Production and Economics of All-Male Tilapia (Oreochromis niloticus) Culture in a Rain Fed Rice-Fish Ecosystem

Effects of stocking density on the growth, production, and economics of all-male tilapia (Oreochromis niloticus) were investigated in a rain-fed rice-fish ecosystem for a period of 120 days. Fish were stocked at the rate of 4000, 5000, and 6000 ha−1 in treatments T1, T2, and T3, respectively. Water quality was suitable for fish culture. Significantly higher growth was observed in T1 as compared to other treatments. SGR ranged from 1.26 to 1.51. Survival varied between 79% and 88% with treatment T1 producing the highest survival. The highest benefit:cost ratio was obtained in T2 followed by T1 and T3. The best fish production (457.21 kg ha−1) and economic return for the culture period was obtained at 5000 fish ha−1.

On-Farm Participatory Technology Development Effects on Resource Conservation Technologies in Rainfed Upland Paddy in Himachal Pradesh, India

Rice is a major cereal crop in Himachal Pradesh, a Himalayan state of India, where paddy acreage is about 78,000 ha with a low average yield of 19.62 q ha−1 due to rainfed upland farming. High seeding rates and poor resource-use efficiency of conventional fertilizer nitrogen (N) management practices in rainfed upland paddy have also been major production constraints in rainfed upland ecosystems. To validate and refine the production technology on seed rate and fertilizer N management, the Farm Science Centre, Sundernagar, India, conducted numerous on-farm trials (OFTs) during 2006–2010 under an on-farm participatory technology development approach to enhance resource use efficiency through these resource conservation technologies and boost the paddy productivity in the region. Results of two OFTs conducted during Kharif 2006 in the Mandi District of Himachal Pradesh on different seed rates under different sowing methods on VL Dhan-221 and Sukaradhan-1 (HPR-1156) cultivars suitable for rainfed upland conditions revealed that the seed rate at 80 kg ha−1 sown in rows 20 cm apart resulted in the greatest average paddy productivity to the tune of 25.6 q ha−1 besides greater profitability, followed by a seed rate at 60 kg ha−1 sown in rows 20 cm apart (25.2 q ha−1), over the earlier State Agricultural University (SAU)–recommended practice, that is, seed rate at 100 kg ha−1 in rows 20 cm apart. This refinement in the seed rate was accepted by the participating farmers of the region. The greatest average benefit/cost (B/C) ratio was observed in plots with seed rate at 60 kg ha−1 sown in rows 20 cm apart. Based on these results and data compilation from other locations of the state, now the SAU has refined the seed rate from earlier recommendation of 100 kg ha−1 to 60 kg ha−1 in rows 20 cm apart as well as 80 kg ha−1 through broadcast method under rainfed upland paddy in Himachal Pradesh. Results of two OFTs conducted during Kharif 2009 on integrated nutrient management in rainfed upland paddy revealed that farmyard manure (FYM) at 10 t ha−1 + nitrogen, phosphorus, and potassium (N, P, K) at 15:30:30 kg ha−1 at sowing followed by 15 kg N ha−1 15 days after sowing (DAS) and remaining the N [i.e., 30 kg N ha−1] at tillering (45–50 DAS) resulted in the greatest grain yield of 29.85 and 31.67 q ha−1 in VL Dhan-221 and HPR-1156, respectively, with respective greater yields of 35.99 and 36.51% over farmers’ practice, besides better profitability. To further standardize fertilizer N split doses and assess their effect on paddy productivity, another OFT was conducted during Kharif 2010 under rainfed upland paddy conditions in HPR-1156. The results revealed that NPK at 60:30:30 kg ha−1 (whole of P and K as basal, 50% N at 15 DAS, 25% N each at 45–50 DAS and 70–75 DAS splits) resulted in better grain yield (34.3 q ha−1) and net profitability (₹29,786 ha−1) over other treatments. Overall, it is concluded that these resource conservation technologies developed under the OFT participatory approach can enhance the rainfed upland paddy productivity and strongly show that there is dire need to split the N requirement of rainfed upland paddy in 2–3 splits to reduce the fertilizer N losses, enhance resource-use efficiency, and increase productivity and profitability in Himachal Pradesh, India.

Land degradation and integrated watershed management in India

In view of the stagnating productivity levels of irrigated agriculture, the contribution from rainfed agriculture should be increased to meet the requirements from the ever growing human and animal population of India. Land degradation is a major threat to our food and environment security and the extent of degradation problems are more pronounced in rainfed regions. Large potential of rainfed agriculture is untapped largely due to lack of enabling policy support and investments. In drought-prone rainfed areas, watershed management has shown the potential of doubling the agricultural productivity, increase in water availability, restoration of ecological balance in the degraded rainfed ecosystems by greening these areas and diversification of cropping farming systems. Impact of various watershed programmes can be substantially enhanced by developing new approaches and enabling policies new paradigm based on learnings over last 30 years for people-centric holistic watershed management involving convergence, collective action, consortium approach, capacity development to address equity, efficiency, environment and economic concerns is urgently needed. However, this can be used as entry point activity for improving livelihood for rural community.It has been realized that for sustainable developments of degraded lands, involvement of people (land less and beneficiaries) is very much essential. For the last decade efforts have been made institutionalize the organizations of the community & beneficiaries and ensuring their involvement in planning project formulation, implementation and maintenance.Government of India has launched various centre-sector, state-sector and foreign aided schemes for prevention of land degradation, reclamation of special problem areas for ensuring productivity of the land, preservation of land resources and improvement of ecology and environment. These schemes are being implemented on watershed basis in rainfed areas. Soil conservation measures and reclamation of degraded lands are decided considering the land capability and land uses. The efforts made so far resulted in enhancement of agricultural production and productivity of lands, increase in employment generation, improving the environment of the areas and socio-economic upgradation of the people. Integrated watershed management approach has been adopted as a key national strategy for sustainable development of rural areas. This has been proved by conducting monitoring and impact evaluation studies of the integrated watershed projects by external agencies.

ABIOTIC STRESS RESPONSES IN TEA [&lt;i&gt;Camellia sinensis&lt;/i&gt; L (O) Kuntze]: AN OVERVIEW

Abiotic stress is limiting to tea productivity. The severity and duration of the abiotic stress are critical, as it has multifarious effectson crop plants. The tea plant is commonly grown in rain-fed ecosystems and thus it encounters seasonal water deficit conditions thatinduce loss in crop yield. In this review, we have highlighted the effects of abiotic stress (drought, metal etc.) on the growth, mineralnutrition, reactive oxygen species (ROS), and antioxidant metabolism in tea plants. This article also highlights the mechanism ofdrought stress amelioration in tea plants on a physiological and biochemical basis. Drought stress caused increased water loss rate (WLR)and decrease in relative water content (RWC), dry mass, chlorophyll, carotenoid, and total phenolic contents of leaf and antioxidantslike ascorbate and glutathione in tea. Leaf antioxidant enzymes (e.g., SOD, CAT, GR, etc.) showed differential activities whereas therewas increase in ROS and lipid peroxidation with decreased POX activities with progressive stress. Drought stress altered antioxidativeresponse with apparent decrease in mineral nutrient (Zn, Ca, Na, Fe, Mg, and K) contents of leaves suggesting that mineral deficiencymediated drought stress induced oxidative damage in tea. Tea plants exposed to heavy metals (e.g., Cd, Cu, Al) also showed reductionin growth and antioxidative responses. Further, a post-drought recovery study in tea also reveals that drought induced biochemicaldamages are not permanent, as the plant recovers on rehydration. Mineral nutrients play an important role in post-drought recovery intea. The process of recovery was significantly influenced by foliar spray of K, Ca, Zn etc., leading to improved antioxidant potential.Thus, drought tolerance and post-drought recovery can be improved by application of nutrients like K, Ca, Zn, B etc. However,molecular mechanisms of abiotic stress amelioration and post stress recovery mediated by these nutrients need to be explored in future.

Identification of Superior Segregants for Drought Tolerance and Productivity Traits in Backcross Inbred Lines (BILs) Derived from NERICA Introgression under Rainfed Ecosystem

The aim of this study was to identify promising genotypes for upland rice ecosystem especially in drought prone areas. Backcross inbred line (BC 1 F 6 ) developed from inter varietal cross of Swarna X NERICA were evaluated under water stressed environment for physiological and productivity related traits in the pot experiment. The result showed a clear expression of donor (NERICA) genome on the background of the recurrent parent (Swarna) in the BILs evaluated. Performance of BILs is generally lower under water stressed treatment when compared with non-stressed treatment for all the traits studied except leaf temperature which was higher under water stressed condition. Except for traits like leaf area and plant height, percentage reduction in performance of BILs for physiological and productivity component traits under water stress treatment are generally lower than the recurrent parent Swarna indicating their superiority over recurrent parent for drought tolerance.

Evaluation of rice (Oryza sativa L.) near iso-genic lines with root QTLs for plant production and root traits in rainfed target populations of environment

Drought stress is the major constraint in rainfed rice production. Deep and thick roots are thought to contribute in drought resilience. Selection for root traits is hampered by difficulty in phenotypic measurements. Mapping quantitative trait loci (QTLs) for root traits and their use in marker assisted breeding (MAB) will hasten the development of genotypes with improved root system. Consistent QTLs for root traits have been mapped in rice. Developing and testing near iso-genic lines (NILs) with QTLs for root traits in target populations of environment (TPE) will help to verify the agronomic value of the QTLs. NILs were developed by introgression of three root QTLs from CT9993, an upland japonica into IR20, a lowland indica cultivar through MAB. Considerable variation in drought response and grain yield under rainfed condition in TPE was observed among the NILs. Five out of 41 NILs gave higher yields under rain-fed and irrigated conditions as compared to IR20. Two NILs viz., 212 and 297, with three and two root QTLs, respectively had thicker and longer nodal roots and higher total and deep nodal root weights than IR20. In addition, NIL 297 had more nodal root volume and surface area, while NIL 212 had more number of nodal roots compared to IR20. Further evaluation of the NILs with farmers for yield and grain quality may help in identification of high-yielding, resilient rice suitable for drought-prone rainfed ecosystems. The NILs may also be useful to study the genes underlying the QTLs and their functions for drought resilience improvement in rice.

A CRITICAL ASSESSMENT OF THE IMPORTANCE OF SEEDLING AGE IN THE SYSTEM OF RICE INTENSIFICATION (SRI) IN EASTERN INDIA

SUMMARYA survey of the system of rice intensification (SRI)-related literature indicates that different authors have drawn conflicting inferences about rice yield performances under the SRI, chiefly because the SRI methodology has been variously advocated, interpreted and implemented in the field using different rice varieties, seedling ages at transplantation, cultivation seasons and nutrient management regimes. In particular, the SRI method of single-seedling transplantation (SST) has potential economic advantage due to reduced seed costs, but it is not clear whether SST is an effective management strategy across a range of seedling ages, and whether there is any specific seedling age that is optimal for yield improvement of a given rice variety. This is an important consideration in rain-fed ecosystems where variable rainfall patterns and lack of controlled irrigation make it difficult to reliably transplant at a specific seedling age as recommended for the SRI. We conducted a five year-long experiment on a rain-fed organic farm using a short-duration upland and a medium-duration lowland landrace, following the SRI methodology. Rice seedlings of different ages (6, 10, 14, 18 and 28 days after establishment) were transplanted at 25 cm × 25 cm spacing in three replicated plots. The performance for each landrace was examined with respect to productive tillers, panicle density, total grain counts per hill and grain yield per unit area. Performances of seedlings of different ages were compared with that of control plots that employed all SRI practices with the exception that 28-day-old seedlings were transplanted with three seedlings per hill. The results indicate that (1) the SRI can improve mean panicle density if seedling age ≤ 18 days, but that responses differ between varieties; (2) the number of productive tillers per hill is significantly less in SST than that of multiple seedling transplants (MST) of 28-day-old seedlings of both upland and lowland varieties; (3) the total grain numbers per hill of the lowland variety is significantly greater for 14-day-old SST than 28-day-old MST; (4) the grain yield per unit area from young SRI transplants is significantly greater than that from 28-day-old MST for the lowland variety, although the magnitude of the improvement was small; (5) for the upland variety, grain yields declined with the oldest seedlings, but planting multiple seedlings per hill made the yield of the oldest transplants on par with that of younger seedlings planted singly. Our findings suggest that transplanting younger seedlings under the SRI management may not necessarily enhance grain yields.

Effect of nutrient management and straw mulching on crop yield, uptake and soil fertility in rapeseed (Brassica campestris)–greengram (Vigna radiata)–rice (Oryza sativa) cropping system under Gangetic plains of India

An experiment was conducted at Bidhan Chandra Krishi Viswavidyalaya, West Bengal, India during 2001–2003 to study the effect of levels of fertility and straw mulch on a rapeseed (Brassica campestris var yellow sarson)–greengram (Vigna radiata)–rice (Oryza sativa) cropping system under a rainfed upland ecosystem. The experiment was laid out in a split-plot design having 14 treatment combinations of organic and inorganic nutrients along with straw mulch in three replicates. The results revealed that conjunctive use of organic and inorganic nutrients as well as paddy straw mulch resulted higher yield in both rapeseed and greengram, and the residual effects of different levels of fertilization and mulching also gave rise to higher grain yield in the succeeding rice crop. The uptake of nutrients, by the cropping system as a whole, to the tune of 204.29 and 183.00 kg ha−1 of N, 72.84 and 74.07 kg ha−1 of P and 179.95 and 175.41 kg ha−1 of K took place, with the treatment receiving 10 t ha−1 of farmyard manure (FYM) applied (to rapeseed) along with 50% recommended dose (RD) of NPK to all the crops in the sequence in two consecutive years, respectively. The same treatment resulted in a higher percentage of porosity vis-à-vis lower bulk density. Soil physico-chemical properties were superior in mulch-treated plots compared with no mulch treatment. Application of organic and inorganic nutrients along with proper moisture conservation practices can enhance the yields maintaining a good soil health.

Identification of genotypes resistant to blast, bacterial leaf blight, sheath blight and tungro and efficacy of seed treating fungicides against blast disease of rice

A total of 35 inbred and 13 hybrid varieties including susceptible checks were screened against the 4 major diseases of rice (blast, bacterial leaf blight, sheath blight and tungro) as well as experiments on management of blast were conducted in the rain-fed and irrigated rice ecosystems during 1999 to 2003. Results showed that none of the tested high yielding varieties (HYV) were resistant to blast, while the hybrids, sonarbangla1, aalock6201, KRH2, IR71101H, IR68877H and IR76901H, and inbreds BR12, BR15 and IR72 were moderately resistant in the irrigated rice ecosystem. On the other hand, all the varieties tested against bacterial leaf blight (BLB) and sheath blight (ShB) were moderately susceptible in the same ecosystem. The inbred varieties BR22, BR25, BRRI dhan31, BRRI dhan32, BRRI dhan33, BRRI dhan34, BRRI dhan38 and BRRI dhan39 demonstrated moderately resistant reactions but all the hybrids were moderately susceptible to BLB in the rain-fed ecosystem. Eight inbreds, predominantly, BR22, BR23, BRRI dhan27, BRRI dhan31, BRRI dhan32, BRRI dhan37, BRRI dhan38 and BRRI dhan40 were moderately resistant to tungro disease. Among the 3 fungicides tested in 2 different trials, adivistin and haydazim 50 WP (carbendazim) at the rate of 0.4% were more effective as seed-treating fungicides for the control of rice blast disease. Key words: Hybrids, inbreds, screening genotypes, major rice diseases, seed-treating fungicides.

Soil temperature, water use and yield of yellow sarson ( Brassica napus L. var. glauca) in relation to tillage intensity and mulch management under rainfed lowland ecosystem in eastern India

The rainfed, lowland ecosystem in the Lower Gangetic Plain of eastern India is characterized by fine-textured soils, bowl shaped topography, stagnation of rainwater and chances of flash floods. The area is mostly covered with long duration (≥150 days) rice varieties during the rainy season and thereafter the land remains fallow. The uncropped fallow period represents a waste of resources and a new crop management package would be desirable to encourage effective utilization of soil and water resources. A study was carried out on a Gayeshpur clay loam soil (fine loamy Aeric Haplaquept) during the winter months of 1996–1997 and 1997–1998 to evaluate the role of tillage intensity and mulch management on the temperature of upper soil layers (0.0–0.2 m), moisture depletion pattern and yield and water use efficiency of yellow sarson ( Brassica napus L. var. glauca). Zero-till (ZT) and conventional tillage (CT, two cross-wise passes with a rotary power tiller) were main plots and three mulch treatments were sub-plots: no mulch (NM), dry water hyacinth mulch (HM) and rice straw mulch (SM). Morning soil temperature at 0.0–0.2 m depth was 0.1–0.8 °C higher under CT than under ZT. The difference was only 0.1–0.4 °C at 14:00 h. Seed yield of yellow sarson under ZT was 1175 kg ha −1, which was 25% higher than under CT. Highest (1212 kg ha −1) seed yield was obtained under SM, which was 7 and 41% higher than under HM and NM, respectively. Water use efficiency (WUE) under ZT was 17% greater than under CT. The WUE was enhanced 45 and 37% under SM and HM, respectively, when compared with NM. In a lowland rainfed ecosystem, adoption of ZT and organic mulching would utilize the residual soil moisture following rice, resulting in rice–yellow sarson as a viable profitable cropping system.

Nitrogen fertilizer optimization and cultivar selection for rice grown near mountainous slopes in Orissa, India

Degradation of the natural resource base has led to decline in crop yields or stagnation that caused food shortages at varying degrees among mountain families. Rice, the major staple food in Asia, is suffering from lack of suitable cultivar and N fertilizer management, when grown near mountainous slopes under rain-fed agro-ecosystem. An investigation through a field experiment and simulation study was conducted at United Nations University, Tokyo to select suitable rice cultivars and N fertilizer level for the rice grown near mountainous slopes in Orissa, India. The field experiment was conducted during wet season (June to November) of 2001 at Kasiadihi village of Dhenkanal district, Orissa, India with eight popular rice cultivars of medium (120–130 d) and long duration (135–150 d) group and four N levels (0, 40, 80 and 120 kg·ha−1). Highest grain yield of 5,680 kg·ha−1 was obtained from cultivar Ranjit of long duration group followed by 4,730 kg·ha−1 from cultivar Mahamaya of medium duration group, across N levels. CERES-Rice model was used to simulated grain yield of these two selected cultivars using historical weather data of the past 18 years (1983–2000). Long duration cultivar Ranjit registered higher yield with lower stability as compared medium duration cultivar Mahamaya over the past 18 years. An optimum N fertilizer level of 80 kg·ha−1 was recommended for rice grown under rain-fed ecosystem near mountainous slopes in Orissa, India to attain optimum yield potential of cultivar.

Methane emission from rice fields at Cuttack, India.

Methane (CH4) emission from rice fields at Cuttack (State of Orissa, eastern India) has been recorded using an automatic measurement system (closed chamber method) from 1995–1998. Experiments were laid out to test the impact of water regime, organic amendment, inorganic amendment and rice cultivars. Organic amendments in conjunction with chemical N (urea) effected higher CH4 flux over that of chemical N alone. Application of Sesbania, Azolla and compost resulted in 132, 65 and 68 kg CH4 ha−1 in the wet season of 1996 when pure urea application resulted in 42 kg CH4 ha−1. Intermittent irrigation reduced emissions by 15% as compared to continuous flooding in the dry season of 1996. In the wet season of 1995, four cultivars were tested under rainfed conditions resulting in a range of emissions from 20 to 44 kg CH4 ha−1. Application of nitrification inhibitor dicyandiamide (DCD) inhibited while Nimin stimulated CH4 flux from flooded rice compared to that of urea N alone. Wide variation in CH4 production and oxidation potentials was observed in rice soils tested. Methane oxidation decreased with soil depth, fertilizer-N and nitrification inhibitors while organic amendment stimulated it. The results indicate that CH4 emission from the representative rainfed ecosystem at the experimental site averaged to 32 kg CH4 ha−1 yr−1.