Rice Monocropping Research Articles

Rice based farming system models for enhancing profitability of small farm holders in Telangana

Rice is cultivated on an area of about 1.67 million hectares with a production of 4.9 million tonnes in Telangana. The study has assessed the profitability of the major rice based integrated farming systems in Rangareddy district of Telangana. The data for the study were collected from 36 small holder rice farmers of three villages of Rangareddy district during 2016. The rice based integrated farming systems evaluated include, rice-rice, rice-pigeonpea-vegetable, rice-vegetable-dairy, ricecotton-vegetable, rice-vegetable-dairy, rice-vegetable-sheep and rice-vegetable-fodder-dairy. The results indicate that the rice based farming systems allows farmers to realise higher profits than the conventional mono cropping of rice. The integration of rice with vegetable cultivation and pigeonpea cultivation/sheep/dairy resulted in higher B:C ratio than the cultivation of rice alone.

Effects of intercropping rice and water spinach on net yields and pest control: an experiment in southern China

Strategies encouraging the use of fewer agrochemicals while maintaining high yield are highly demanded for smallholder rice farmers. Intercropping helps to suppress pests and disease in upland farming systems. However, information on the role of intercropping in pest suppression and crop productivity in irrigated rice farming systems is sparse. To explore the possibility of establishing diversified agriculture management strategy that requires lower agrochemical inputs, a field study was conducted to evaluate the effect of rice and water spinach intercropping on the occurrence of pests, disease, and land-use efficiency. Results demonstrated that the occurrence of rice blast disease, sheath blight disease, and Cnaphalocrocis medinalis was substantially lower than pure stands. Compared with rice monoculture, the tiller number, net photosynthetic rate, and leaf chlorophyll content were significantly increased in rice at the edge rows adjacent to water spinach in intercropping. Intercropping increased the per unit area yield of rice without significant reduction in that of water spinach. Land equivalent ratio (LER) was 1.13, showing that intercropping was 13% more productive than rice monocropping. Net income for intercropping was 5.04 times higher than for rice monocropping. These findings suggest that rice and water spinach intercropping is a viable alternative for sustainable rice production with a small farming scale in southern China.

Raised and sunken bed land configuration for crop diversification and crop and water productivity enhancement in rice paddies of the north eastern region of India

The crop and water productivity (WP) of monocropped rice in lowland of north-eastern region of India is low mainly due to cultivation of long duration variety, meagre use of fertilizer and manure, and inefficient water management, which needs to be improved for sustaining food security. Raised and sunken bed (RSB) land configuration (removing the surface soil layer from an area and depositing on the adjacent area to a height of about 50 cm by cutting and filling method) was demonstrated in a participatory research mode in farmers’ field during 2010–2012 for promoting crop diversification, enhancing crop and WP, and improving livelihood. The results indicated significant improvement in cropping intensity, productivity, employment, and income of farmers due to adoption of RSB land configuration compared to farmers’ practice (FP) of rice monocropping. The average rice equivalent yield (REY) of RSB land configuration was 16.20 t ha−1 compared to 3.24 t ha−1 under FP. The enhancement in employment and water-use efficiency were 445 and 291 % due to RSB over FP, respectively. The WP enhanced by four times due to RSB (0.69 kg m−3 water) compared to FP (0.18 kg m−3 water). In raised beds, the highest gross (USD 7,346 ha−1) and net returns (USD 4,524 ha−1) were recorded under tomato–okra–broccoli sequence, while in sunken beds, the highest gross and net returns were obtained under rice–pea (USD 2,633 and 1,590 ha−1, respectively) and these were substantially higher than those observed under FP (USD 775 ha−1 and USD 383 ha−1, respectively). Multiple cropping index, cultivated land utilization index, and diversity index also increased substantially due to RSB land configuration.

Crop diversification, crop and energy productivity under raised and sunken beds: results from a seven-year study in a high rainfall organic production system

Low productivity, crop diversification, employment and income are the major constraints of existing production systems of the high-rainfall north-eastern hill region (NEHR) of India. Field experiments were conducted for seven consecutive years to evaluate crop performance, production and energy balance of cropping sequences under raised and sunken bed (RSB) systems in mid-hills (950 m above mean sea level) of subtropical Meghalaya, India. Five vegetable-based cropping sequences on raised beds and six rice-based sequences on sunken beds were tested and compared with rice monocropping (control) under an organic production system. On raised beds, tomato–okra–French bean gave highest rice equivalent yield (REY; 44.7 t ha− 1) followed by carrot–okra–French bean (42.5 t ha− 1). Rice (cv. Shahsarang 1)-pea (cv. Prakash) gave highest REY (17.3 t ha− 1) on sunken beds. Among raised bed sequences, tomato–okra–French bean recorded greatest production efficiency (162 kg ha− 1 day− 1) and carrot–okra–French bean recorded highest land use efficiency (77%). Employment was enhanced by 187% with potato–okra–French bean and 181% with tomato–okra–French bean on raised beds, whereas rice–pea sequence on sunken beds enhanced employment by 62% over monocropping of rice. The energy productivity (energy output/input) was also higher with these cropping sequences. The adoption of RSB land configuration facilitated 244% cropping intensity (gross cultivated area/net cultivated area × 100) compared with 100% in rice monocropping. There was a significant improvement in soil chemical and biological parameters due to continuous organic production under RSB land configuration, indicating potential for organic farming in the subtropical hill ecosystem of India.

Effect of Intercropping of Sesbania rostrata with Transplant Aman Rice on Yield and Profitability

The effect of intercropping of Sesbania rostrata with Transplant Aman rice on yield and profitability was determined at the Agronomy Field Laboratory, Bangladesh Agricultural University, Mymensingh, from July to December 2009. The experiment consisted of five treatments viz.; i) intercropping Sesbania in between two rows of rice, ii) intercropping Sesbania in two rows interval of rice , iii) intercropping Sesbania around the rice field, iv) sole rice and v) sole Sesbania rostrata. The results revealed that rice grain yield decreased to a significant level by Sebania intercropping compared to sole rice which varied from 11.43 to 28.21%, with the maximum (28.21%) by intercropping Sesbania in between two rows of rice followed by intercropping Sesbania in two rows interval of rice (12.5%) against the minimum (11.43%) by intercropping Sesbania around the rice field. In terms of total rice grain yield equivalent (TRGYE), the highest TRGYE (6.88 ton ha -1 ) was recorded for the treatment of intercropping Sesbania in two rows interval of rice followed by intercropping Sesbania in between two rows of rice (6.00 ton ha -1 ) and intercropping Sesbania around the rice field (5.87 ton ha -1 ) against the minimum (5.60 ton ha -1 ) for sole rice clearly indicating yield advantages of intercropping over monocropping of rice. Similarly the net field benefits obtained from different intercropping systems were considerably higher than the sole cropping of rice. The maximum net benefit of Tk.73531 ha -1 was recorded for intercropping Sesbania in two rows interval of rice which is 26.68% more than sole rice (Tk. 59620 ha -1 ).

Synergic Effect of Flooding and Nitrogen Application on Alleviation of Soil Sickness Caused by Aerobic Rice Monocropping

The “aerobic rice” system is the cultivation of high yielding rice cultivars under non-flooded conditions in non-puddled (aerobic) soil with supplemental irrigation. The major constraint in wide adoption of aerobic rice technology is soil sickness caused by continuous monocropping due to still unknown factors. The possible role of flooding and nitrogen application in alleviating the soil sickness caused by continuous monocropping of aerobic rice was examined by pot experiments. Plants were grown aerobically or anaerobically on the soil collected from a field grown with aerobic rice for 12 consecutive seasons. The results showed that flooding alleviated soil sickness, but not as much as soil oven-heating treatment (120ºC for 12 hr). Application of ammonium sulfate improved plant growth up to the level of oven-heating treatment, while ammonium sulfate application and flooding exceeded the soil oven-heating treatment significantly. The synergy of flooding with ammonium sulfate application was greater than that with urea. These results suggest that soil sickness caused by continuous aerobic monocropping can be alleviated by flooding and ammonium sulfate application.

Integrated Rice-Fish Farming: Safeguarding Biodiversity and Ecosystem Services for Sustainable Food Production in the Mekong Delta

A comparison of agricultural practices, with a specific focus on pesticide use, between rice and rice-fish farmers in the Cần Thơ and Tiền Giang provinces of the Mekong Delta in 2007, shows that integrated rice-fish farming can provide a competitive alternative to intensive rice mono-cropping, if the farmer restricts the use of pesticides and takes full advantage of the ecosystem services provided by the rice-field ecosystem. In Cần Thơ, rice-fish farmers had significantly higher income (43.6 million dong ha−1 year−1) than other farmer groups, while this was not seen among rice-fish famers in Tiền Giang (32.4 million dong ha−1 year−1), which partly could be due to a high use of insecticides (0.9 kg active ingredient ha−1 crop−1) and comparatively low fish yield among these farmers. The study emphasizes the need to rethink current agricultural systems and to provide opportunities for more diverse systems that maintain and enhance a range of ecosystem services and protect human health. Future production systems should not be optimized to only provide a single ecosystem service, such as rice, but designed to deliver a variety of interlinked ecosystem service such as rice, fish, pest control, and nutrient recycling.

Different farming and water regimes in Italian rice fields affect arbuscular mycorrhizal fungal soil communities

Arbuscular mycorrhizal fungi (AMF) comprise one of the main components of soil microbiota in most agroecosystems. These obligate mutualistic symbionts colonize the roots of most plants, including crop plants. Many papers have indicated that different crop management practices could affect AMF communities and their root colonization. However, there is little knowledge available on the influence of conventional and low-input agriculture on root colonization and AMF molecular diversity in rice fields. Two different agroecosystems (continuous conventional high-input rice monocropping and organic farming with a five-year crop rotation) and two different water management regimes have been considered in this study. Both morphological and molecular analyses were performed. The soil mycorrhizal potential, estimated using clover trap cultures, was high and similar in the two agroecosystems. The diversity of the AMF community in the soil, calculated by means of PCR-RFLP (polymerase chain reaction-restriction fragment length polymorphism) and 18S rDNA sequencing on clover trap cultures roots, was higher for the organic cultivation. The rice roots cultivated in the conventional agrosystem or under permanent flooding showed no AMF colonization, while the rice plants grown under the organic agriculture system showed typical mycorrhization patterns. Considered together, our data suggest that a high-input cropping system and conventional flooding depress AMF colonization in rice roots and that organic managements could help maintain a higher diversity of AMF communities in soil.

Crop diversification in Thailand: Status, determinants, and effects on income and use of inputs

Following the national policy, the Department of Agriculture of Thailand has implemented a crop diversification program in several provinces of the country. This study, which was conducted in Nakhon Pathom Province, analyzed the extent of crop diversification and its determinants using primary information collected from 245 farm households using a structured questionnaire, and from selected farmer leaders and agricultural development officials. The study also assessed the effects of crop diversification on income and the inputs used. The findings of the study revealed that nearly three fourths of the land is still being used for rice mono-cropping, indicating little success in the promotion of the crop diversification program. Paddy fields, including farms for cultivating rice under mono-cropping and diversified system, still account for 90% of the total farmland in the country. The limited impact of the program on the farming sector is attributed primarily to the variation in land and labor resources available at the farmers’ disposal as well as soil suitability. The farmers’ attendance in training and interaction with farmer groups are the other influential factors. Although cropping diversification has provided attractive financial return particularly to the small farmers, it has also accelerated the use of inorganic fertilizers and pesticides. Broad policy instruments are therefore suggested for the effective implementation of future crop diversification programs in Thailand and perhaps elsewhere in Southeast Asia.

Performance evaluation of concurrent rice-fish-prawn culture with and without cull harvesting

This study was carried out in farmers' fields for three experimental culture cycles to evaluate the performance of rice–fish–prawn culture. The treatments carried out were deepwater rice mono-cropping (R), and rice–fish–prawn culture with cull harvesting (R–FC) and without cull harvesting (R–F). Water pH and total alkalinity were significantly higher (P<0.05) in R–FC than in R–F, while the concentrations of total suspended solids, plankton and chlorophyll a were higher in R–F. Cull harvesting in R–FC had no marked influence on the concentrations of dissolved oxygen, NH4+, nitrite, nitrate and phosphate compared with the R–F treatment. The significantly higher fish and prawn yields (P<0.05) and species-wise faster individual growth performance in R–FC than in R–F were probably due to periodic cull harvesting, which minimized the competition for food and space as well as physiological stress at reduced density. The paddy yield and percentage increase in paddy yield over rice mono-crop was significantly higher (P<0.05) in R–FC (25%), followed by R–F (16.9%), probably due to lower chlorophyll a (36.7 mg m−3) and plankton density (1.4 × 104 L−1), which minimized the competition for nutrients with rice plants. The highest rice equivalent yield (38.5), output value–cultivation cost ratio (1.56) and enhanced net return (28%) in deepwater rice–fish culture were recorded when cull harvesting was practiced.

Evaluation of comprehensive benefit of rice-fish agriculture and rice monocropping—A case study of Qingtian County, Zhejiang Province

农业是整个国民经济发展的基础, 不可否认现代化大规模农业生产在保障粮食数量安全方面贡献巨大, 但在一些适合小规模耕作的山区, 经典的传统农业模式比常规农业耕作方式更具优势。本文基于生态价值观, 以浙江省青田县稻鱼共生系统和常规稻作系统为例, 针对农户和国家两个不同层次主体, 综合计算了上述两种农业生产模式的效益。结果表明, 就直接经济收入而言, 稻鱼共生系统的净收入比常规稻作系统高2 184元·hm^-2, 投入多1 453元·hm^-2, 其投入产出比和投资利润率较低; 但若考虑社会-经济-生态综合效益, 稻鱼共生系统的生态系统服务价值比常规稻作系统高7 447元·hm^-2, 平均每公顷的综合价值高9 631元, 同时其投入产出比和投资利润率优于常规稻作系统。基于效益分析, 稻鱼共生系统的补偿标准下限为6 532元·hm^-2, 上限为16 045元·hm^-2, 政府可以通过对农户的补贴实现直接经济价值和社会综合效益的双赢。

Impact of high-density stocking and selective harvesting on yield and water productivity of deepwater rice–fish systems

We examine the productivity of deepwater rice�fish systems and management strategies that include high-density initial stocking and selective harvesting. All species of fish and prawns grow faster after 120 days of rearing, probably due to periodic selective harvesting that minimizes the competition for food and space, as well as physiological stress at reduced density. We observe a higher survival rate, a lower apparent feed conversion ratio (1.77) and higher fish yield (14.1%) in rice�fish culture with selective harvesting (T1) than in rice�fish culture without selective harvesting (T2). The highest paddy yield was recorded in T1, primarily due to the higher number of panicles per m2 (139.5) and the number of filled grains per panicle (111.5). The increase in paddy yield over rice mono-cropping was higher in T1 (25%) than T2 (16.9%). The smaller number of panicles (122.2/m2) and filled grains (98.5 per panicle) in rice mono-cropping was probably due to the absence of fish and prawns in the field as fish and prawns improve soil fertility, recover lost energy, and adjust energy flow by consuming plankton, weeds, insects and bacteria that compete with rice for nutrients. The highest rice equivalent yield (38.5 t ha-1), the output value-cultivation cost ratio (1.56) and net water productivity (Rs. 7.30/m3) in deepwater rice�fish culture was recorded when selective harvesting was practiced. This eco-friendly dual production system (rice and fish) and on-dyke horticulture, which generate near-term lucrative returns and generates employment opportunities, can be adopted and expanded in lowlands and waterlogged areas

Effect of Organic Residue Management on Soil Hydro-Physical Characteristics and Rice Yield in Eastern Himalayan Region, India

Monocropping of lowland rice is the predominant system in valley land and high-rainfall regions of northeastern India. Recently, the unsustainability of this system has owing to soil structural deterioration and nutrient depletion, become evident, resulting from continuous puddling on the same piece of land even if recommended inorganic fertilizers have been applying regularly. To regenerate and maintain soil structure in rice fields, farmers in this region frequently use farm yard manure (FYM), but low availability of FYM because of its other uses indicates that it could not meet the organic matter requirements of this system. We evaluated the long-term effects of different locally available jungle grasses and weeds on soil hydro-physical properties and rice yield through a 5-year field experiment (2000 to 2005) at the Indian Council of Agricultural Research (ICAR) Complex for North Eastern Hilly (NEH) Region, Umiam, Meghalaya, India and also compared their negative or positive effects with FYM in acidic, Typic Hapludalf soil. The objective was to determine whether locally available grasses (Jungle grass) and weeds (Ambrosia sp.) could be used as alternative sources of organic materials for lowland rice in scarcity of FYM. Results showed that incorporation of FYM or jungle grass or Ambrosia sp., continuously for 5 years in puddled rice soil improved soil organic carbon (SOC) by 21.1%; the stability of micro-aggregates, moisture retention capacity, and infiltration rate of the soil by 82.5, 10, and 31.3%, respectively; and soil bulk density decreased by 12.6%. Application of FYM produced better soil physical environment than that under jungle grass and Ambrosia sp. However, as these grasses and weeds contained higher nutrient levels than FYM and increased the SOC slowly, these organics may serve as alternative to FYM and may have a dramatic effect on long-term productivity of rice. The gradual improvement in soil physical properties led to a significantly higher yield of rice. We conclude that applying organic manure or organic residue annually may mitigate the negative effect of puddling and related properties and therefore could contribute to the sustainability of the wetland rice ecosystem.

METHANE EMISSION FROM TWO DIFFERENT RICE ECOSYSTEMS ( AHU AND SALI ) AT LOWER BRAHMAPUTRA VALLEY ZONE OF NORTH EAST INDIA

Monocropping of rice is practiced in Assam (situated at north east part of India) throughout the year in different agro-ecosystems (upland and lowland) primarily under rainfed conditions. The estimation of methane emission has been realized investigating high yielding rice varieties viz. Ranjit and Mahsuri, grown under two different agro-ecosystems at Lower Brahmaputra Valley Zone of Assam with sandy to sandy loam type of soil. Variety 'Ranjit' grown at monsoon ( Sali ) rice ecosystem at lowland rainfed condition showed higher seasonal integrated methane flux value compared to variety 'Mahsuri' grown at pre monsoon ( Ahu ) rice ecosystem. Both varieties showed two methane peaks, one at the active tillering stage and the second at the reproductive stage of the crop. The observed variation in methane emission peaks are contributed mainly by physiological characteristics of the rice plant such as leaf numbers, tiller numbers, plant height, root shoot biomass and leaf area index. Statistical analysis of these parameters showed a positive correlation with methane emission. These physiological parameters are in turn governed by plant genotypes and environment i.e., the field water availability and climatological factors (rainfall and temperature) during the growing season. While comparing the two ecosystems it was found that methane emission is significantly less from upland rainfed rice ecosystem and this ecosystem can be considered a suitable option for biological mitigation of methane from rice paddies.

Alleviating soil sickness caused by aerobic monocropping: Responses of aerobic rice to nutrient supply

Yield decline is a major constraint in the adoption of monocropping of aerobic rice. The causes of the yield decline in the continuous aerobic rice system are still unknown. The objective of this study was to determine if nutrient application can mitigate the yield decline caused by continuous cropping of aerobic rice. Micro-plot experiment was conducted in 2005 dry season (DS) in a field where aerobic rice has been grown continuously for eight seasons from 2001 DS at the International Rice Research Institute (IRRI) farm. Pot experiments were done with the soil from the same field where the micro-plot experiment was conducted and aerobic rice has been grown continuously for 10 seasons. Apo, an upland rice variety, was grown under aerobic conditions with different nutrient inputs in field and pot experiments. The field micro-plot experiment showed that micronutrients had insignificant effect on plant growth under continuous aerobic rice cultivation but the combination of N, P, and K mitigated the yield decline of continuous aerobic rice. A series of pot experiments studying the individual effects of nutrients indicated that N application improved plant growth under continuous aerobic rice cropping, while P, K, and micronutrients had no effect. Increasing the rate of N application from 0.23 to 0.90 g per pot in the continuous aerobic rice soil increased the vegetative growth parameters, chlorophyll meter readings, and aboveground N uptake consistently. Our results suggested that N deficiency due to poor soil N availability or reduced plant N uptake might cause the yield decline of continuous cropping of aerobic rice.

Alleviating soil sickness caused by aerobic monocropping: responses of aerobic rice to soil oven-heating

“Aerobic rice” system is the cultivation of nutrient-responsive cultivars in nonflooded and nonsaturated soil under supplemental irrigation. It is intended for lowland areas with water shortage and for favorable upland areas with access to supplementary irrigation. Yield decline caused by soil sickness has been reported with continuous monocropping of aerobic rice grown under nonflooded conditions. The objective of this study was to determine the growth response of rice plant to oven heating of soil with a monocropping history of aerobic rice. A series of pot experiments was conducted with soils from fields where rice has been grown continuously under aerobic or anaerobic (flooded) conditions. Soil was oven heated at different temperatures and for various durations. Plants of Apo, an upland variety that does relatively well under the aerobic conditions of lowland, were grown aerobically without fertilizer inputs in all six experiments. Plants were sampled during vegetative stage to determine stem number, plant height, leaf area, and total biomass. Heating of soil increased plant growth greatly in soils with an aerobic history but a relatively small increase was observed in soils with a flooded history as these plants nearly reached optimum growth. A growth increase with continuous aerobic soil was already observed with heating at 90°C for 12 h and at 120°C for as short as 3 h. Maximum plant growth response was observed with heating at 120°C for 12 h. Leaf area was most sensitive to soil heating, followed by total biomass and stem number. We conclude that soil heating provides a simple and quick test to determine whether a soil has any sign of sickness that is caused by continuous cropping of aerobic rice.

Nitrogen fixation and N transfer from peanut to rice cultivated in aerobic soil in an intercropping system and its effect on soil N fertility

The novel cultivation of paddy rice in aerobic soil reveals the great potential not only for water-saving agriculture, but also for rice intercropping with legumes and both are important for the development of sustainable agriculture. A two-year field experiment was carried out to investigate the yield advantage of intercropping peanut (Arachis hypogaea L., Zhenyuanza 9102) and rice (Oryza sativa L., Wuyujing 99-15) in aerobic soil, and its effect on soil nitrogen (N) fertility. A pot experiment was also conducted to examine the N2-fixation by peanut and N transfer from peanut to rice at three N fertilizer application rates, i.e., 15, 75 and 150 kg N ha−1 using a 15N isotope dilution method. The results showed that the relative advantage of intercropping, expressed as land equivalent ratio (LER), was 1.41 in 2001 and 1.36 in 2002. Both area-adjusted yield and N content of rice were significantly increased in the intercropping system while those of peanut were not significantly different between intercropping and monocropping systems. The yields of rice grain and peanut, for example, were increased by 29–37% and 4–7% in the intercropping system when compared to the crop grown in the monocropping system. The intercropping advantage was mainly due to the sparing effect of soil inorganic N contributed by the peanut. This result was proved by the higher soil mineral N concentration under peanut monocropping and intercropping than under the rice monocropping system.%Ndfa (nitrogen derived from atmosphere) by peanut was 72.8, 56.5 and 35.4% under monocropping and 76.1, 53.3 and 50.7% under the intercropping system at N fertilizer application rates of 15, 75 and 150 kg ha−1, respectively. The 15N-based estimates of N transfer from peanut (%NTFL) was 12.2, 9.2 and 6.2% at the three N fertilizer application rates. N transferred from peanut accounted for 11.9, 6.4 and 5.5% of the total N accumulated in the rice plants in intercropping at the same three N fertilizer application rates, suggesting that the transferred N from peanut in the intercropping system made a contribution to the N nutrition of rice, especially in low-N soil.

Does Tephrosia candida as fallow species, hedgerow or mulch improve nutrient cycling and prevent nutrient losses by erosion on slopes in northern Viet Nam?

Agroforestry is considered to be a promising alternative to short-fallow shifting cultivation or other monocropping systems. An on-farm experiment was established in 1996 in northern Viet Nam to examine the contribution of the leguminous bush Tephrosia candida (Roxb.) D.C. as a fallow or hedgerow species and as a mulch producer to improve nutrient cycling and prevent nutrient losses by erosion. The systems tested were upland rice monocropping (Mono), natural fallow (NaFa), fallow of Tephrosia (TepFa), hedgerow intercropping with upland rice ( Oryza sativa L.) and internal mulching using pruned Tephrosia biomass (TepAl), and upland rice with external mulching using Tephrosia biomass (TepMu). Over two cropping seasons, from April 1996 to April 1998, nutrients recycled and inputs and exports were recorded, as well as changes in C-, N- and P-pools, and in pH in the 0–5 cm topsoil layer. The Tephrosia systems (TepFa, TepAl, TepMu) prevented nutrient losses by erosion effectively. Compared to the NaFa system, the TepFa system accumulated 34% more N in the above-ground plant parts and increased topsoil N by 20%, probably due to N-fixation. There was a trend that the less labile P-pools (NaOH-P) were reallocated into the more labile P-pools (Bicarb-P) in the soil of the TepFa system. Burning released significant amounts of the inorganic P-pools in both the NaFa and TepFa systems and this effect seemed to be more pronounced in the TepFa than in the NaFa. Organic input to crop export ratios for N and P were >1 in the TepAl and TepMu treatments. This was due to a sufficient quantity and quality of the Tephrosia mulching material. However, moderately labile NaOH-extractable organic P seemed to be depleted in the topsoil due to high P uptake in the TepMu treatment. Thus, nutrient cycling and nutrient balances were improved under the Tephrosia systems. But for long-term P sustainability, there is a belief that a combined use of mulching and mineral P fertiliser is needed.

Pesticide use in rice and rice–fish farms in the Mekong Delta, Vietnam

Pest management practices among rice and rice–fish farmers and their perception of problems related to pests and pesticides were surveyed in the Mekong Delta. A total number of 64 different pesticides were identified during the survey. Approximately 50% were insecticides, 25% were fungicides and 25% were herbicides. The main insecticides used were pyrethroids (42%) carbamates (23%) and cartap (19%). Non-IPM farmers used twice as many pesticides as IPM farmers. Their application frequency and the amount of active ingredient used were 2–3 times higher per crop, as compared to IPM farmers. During the last three years IPM farmers estimated that they had decreased the amount of pesticides used by approximately 65%, while non-IPM farmers said that they had increased the amount of pesticide used by 40% . Also, farmers growing fish in their rice fields used less pesticide than farmers growing only rice, as pesticides adversely affect cultures of fish. Taking a long-term perspective integrated rice–fish farming with IPM practices provides a sustainable alternative to intensive rice mono-cropping, both from an economic as well as an ecological point of view.

Farming system options for small and marginal holdings in different topographies of Goa

A field experiment was conducted during 1998 2001 at the ICAR Research Complex for Goa, Old Goa, to evaluate suitable integrated farming systems in different topographies. The results revealed that monocropping of rice (Oryza sativa L.) and coconut (Cocos nucifera L.) was not productive in comparison to improved cropping, i.e. rice brinjal (Solanum melongena L.) or coconut forage grass combinations, respectively, and their integrated farming systems (poultry along with mushroom and dairy integration, respectively). Gross returns from lowlands predominated by rice and rice based copping systems were relatively higher (Rs 34,600lha) than from uplands with cashew (Rs 31,4201ha) or midlands and valleys with coconut (Rs 18,3701ha). However, the net returns (Rs 25,020lha) and benefit : cost ratio (3.91) were higher with cashew system, particularly with nut shelling. lntegration of mushroom and poultry production in rice and coconut systems with dairy and value addition in cashew through farming system approach resulted in gross return of R s 98,690lha and net returns of R s 48,00O/ha, although the investment cost was also enhanced substantially (Rs 50,680lha). lntegration of dairy with coconut and forage in tercropping through farming system enhanced the gross returns (Rs 94,870lha) and net returns (Rs 32,335lha) by 5 times over monocropping of coconut, indicating the superiority of the systems approach.