Direct-seeded Aerobic Rice Research Articles

Influence of iron seed priming on seed germination, growth and iron content in rice seedlings

The area under direct-seeded aerobic rice (DSR) is increasing in Indo-gangetic plains due to labor and water scarcity. However, iron (Fe) deficiency is a severe problem in DSR under coarse-textured soils, resulting in poor germination, interveinal chlorosis, and poor seedling establishment. Fe seed priming is a better option to ensure higher seed germination and optimum supply of Fe at initial growth stages. Hence, the experiment was conducted with seven seed priming treatments i.e. Control (hydropriming), 0.5% Fe through ferrous sulfate (FeSO4 7H2O), 1.0% Fe through FeSO4 7H2O, 0.25% Fe through ethylene diamine tetra acetic acid chelated iron (Fe-EDTA), 0.5% Fe through Fe-EDTA, 0.025% Fe through iron oxide nanoparticle (FeO NPs) and 0.05% Fe through FeO NPs. The Fe seed priming showed a significant increase in Fe content of paddy seeds over the hydropriming treatment. Among different treatments, FeSO4.7H2O (1.0% Fe) showed highest germination percentage (91.3%), root length (8.4%) and shoot length (9.4%) followed by FeSO4.7H2O (0.5% Fe) which was significantly higher over the control. But, the treatment involving Fe-EDTA (0.5% Fe) showed adverse effects on germination and seedling growth. Ferrous (Fe2+) iron and total Fe content in rice seedlings showed similar trends to total Fe content in primed seeds treated with different Fe sources. Thus, Fe seed priming of rice with FeSO4.7H2O (1.0%Fe) for 12 h was effective for higher germination percentage, greater iron content at initial growth stages and ameliorated the Fe deficiency in direct seeded aerobic rice.

Enhancing the accumulation and bioavailability of iron in rice grains via agronomic interventions

Suboptimal or inadequate diet of iron (Fe) represents a latent health problem affecting over two billion people worldwide. To tackle micronutrient deficiency in crops, a short-term approach is agronomic biofortification in which nutrients can be enhanced by their accumulation in food plant tissue either by fertilisation or by other eliciting aspects. The present study evaluated the comparative influence of various Fe application methods, including (i) Fe seed coating (300 mg Fe kg–1 seed), (ii) Fe osmopriming (0.5% Fe solution), (iii) surface broadcasting (8 kg ha–1), (iv) Fe foliar application (0.3% Fe solution), on paddy yield, net benefits, grain Fe accumulation, bioavailability, and Fe-use efficiencies in conventional (puddled transplanted rice, PTR) and conservational (direct-seeded aerobic rice, DSAR) production systems. Hydro-priming and foliar water spray were also included in treatments as a positive control for osmopriming and foliar spray of Fe respectively. Iron application by either method enhanced productivity, profitability, and biofortification in both rice systems. Grain yield improved in both years by the application of Fe in the following order: osmopriming > foliar application > surface broadcasting > seed coating, with the respective increase of 18%, 14%, 10%, 8% relative to no Fe application. Grain Fe concentration was the highest by Fe applied as foliar (37% over control) in both production systems. Similarly, minimum phytate concentration and phytate:Fe molar ratio were recorded with foliar-applied Fe. In crux, Fe application by osmopriming increased the productivity and profitability under PTR and DSAR systems, whereas foliar-applied Fe improved the grain Fe accumulation.

Real-time application of neem-coated urea for enhancing N-use efficiency and minimizing the yield gap between aerobic direct-seeded and puddled transplanted rice

Abstract An appropriate nitrogen (N) management strategy is required for minimizing the yield loss incurred in aerobic direct-seeded rice (ADR) due to moisture stress. Field experiments for two consecutive years were conducted to evaluate comparative performance of real-time application of neem-coated urea (NCU) and prilled urea (PU) using a customized leaf color chart (CLCC) on growth, yield and N use efficiency of both ADR and puddled transplanted rice (PTR). Six treatments were tested with cultivar ‘Apo’:0 N (T1) as control, 100 kg N ha−1 as prilled urea (PU) applied conventionally (T2), 100 kg N ha−1 as NCU applied conventionally (T3), 100 kg N ha−1 as PU applied on the basis of CLCC recommendation (T4), 100 kg N ha−1 as NCU applied on the basis of CLCC recommendation (T5), and 50 kg N ha−1 as PU and 50 kg N ha−1 as farm yard manure (FYM) (T6). Results of the field experiments showed significant effects (p ≤ 0.05) of both cultivation method and N management on yield. The ADR produced 22.5–46.0% less yield as compared to PTR mainly due to substantial reductions in leaf area, biomass and sink size. As compared to PU, the conventional application of NCU increased yields by 7.1–13.4 % and 6.8–10.0 %,in ADR and PTR, respectively and the differences were significant (p ≤ 0.05). But when applied using CLCC, yield enhancements from PU increased to 21.2–22.9 % and 14.6–15.9 %, respectively. The NCU resulted in 6.6–8.9 and 6.2–6.5 % higher N recovery efficiency as compared to PU, which was further increased to 16.3–18.0 and 11.4–14.6 % in ADR and PTR, respectively when applied using CLCC. Hence, our results indicate that optimization of N application combining both a real-time N management tool (CLCC) and enhanced efficiency N fertilizer (NCU) could help minimize yield losses, which was more visible under ADR by improving growth and yield parameters. The findings of the present study can be proposed as a suitable alternative to the existing N-fertilizer management for rice farmers of both aerobic dry-seeded and puddled transplanted conditions, while more yield advantage was realized in the former.

Foliar Manganese Supply Enhances Crop Productivity, Net Benefits, and Grain Manganese Accumulation in Direct-Seeded and Puddled Transplanted Rice

Manganese (Mn) deficiency in human nutrition is widespread in the rice–wheat cropping system where cereal grains are the staple food. Agronomic biofortification is an innovative and pragmatic approach to tackle Mn malnutrition. A 2-year field study was conducted to investigate the comparative effect of different Mn application methods: (1) No Mn application, (2) Mn seed coating (2 g kg−1 seed), (3) hydro-priming, (4) Mn seed priming (0.1 M Mn solution), (5) soil application (0.5 kg ha−1), (6) foliar water spray, and (7) foliar Mn spray (0.02 M Mn solution) in improving the productivity, profitability, biofortification and Mn-use efficiencies of rice in puddled transplanted flooded rice (FR) and direct-seeded aerobic rice (AR) production systems. Under AR system, soil physical and biological properties, as well as nutrient dynamics were improved. Averaged across 2 years, improvement in total soil porosity (9%), soil organic carbon (12%), soil microbial biomass carbon (6%), soil microbial biomass nitrogen (3%), total nitrogen (13.6%), available phosphorus (10.98%), and exchangeable potassium (7.1%) were noted in AR system over FR system. Regardless of application methods, Mn nutrition substantially improved the yield and related traits and grain Mn concentration in both production systems. Averaged across 2 years, the increase in grain yield under different Mn application treatments was in the order: foliar application (22%) > seed priming (16%) > soil application (12%) > seed coating (12%). Grain Mn concentration was the highest with foliar application of Mn (27% over control) in both production systems. Moreover, the maximum net benefits and benefit–cost ratio were obtained through Mn-foliar application in both production systems. In conclusion, Mn application by either method improved the productivity, profitability, biofortification and Mn-use efficiencies under FR and AR systems; nevertheless, foliar Mn application performed better for all the studied traits.

Residual zinc improves soil health, productivity and grain quality of rice in conventional and conservation tillage wheat-based systems

Zinc (Zn) deficiency in rotations of rice (Oryza sativa L.) and wheat (Triticum aestivum L.) impedes the productivity of both component crops. Fertilisation with Zn and switching to conservation tillage systems may help to improve soil health and the productivity of both rice and wheat. However, it is not clear whether, in conservation tillage systems, Zn application to either crop will fulfil the requirement of the following crop through a residual effect. This study was designed to evaluate the influence of Zn applied to wheat on the performance of rice under conventional (puddled transplanted rice, PuTR) and conservation (direct-seeded aerobic rice, DSAR) tillage. As a part of a long-term experiment, Zn was applied as foliage spray (FA, 0.025 M), by seed priming (SP, 0.5 M) and by soil application (SA, 10 kg ha–1) in plough-till wheat (PTW) and no-till wheat (NTW). Controls without Zn application were included (PTW-C, NTW-C). After wheat harvest, rice was planted as PuTR and DSAR in each of the eight Zn application × wheat tillage treatment combinations. Compared with PuTR, DSAR significantly improved soil fertility (nitrogen, phosphorus, Zn), soil organic matter (1.5–4.5%), soil organic carbon (3%), soil microbial biomass carbon (2.5%) and grain yield (5.6%). Overall, DSAR preceded by NTW had higher soil organic carbon (4.3%), soil microbial biomass nitrogen (1.6%) and soil microbial biomass carbon (3.7%) than PuTR sown after either PTW or NTW. Residual Zn enhanced grain Zn concentration by 15% in rice planted after PTW-SA and 12% after NTW-SA. Overall order of improvement in rice-grain Zn concentration was PTW-SA = NTW-SA > NTW-C = NTW-SP. Likewise, higher grain yield with residual Zn availability was in the order DSAR-NTW-SA > PuTR-PTW-SA during 2018. Highest economic return with high benefit:cost ratio was recorded for DSAR-NTW-SA. Zinc application to the wheat crop effectively improved crop performance and grain quality of the following rice crop in both conventional and conservation tillage systems. However, the conservation system DSAR-NTW-SA may be chosen for improved soil health, and for increased harvest grain yield with better grain quality.

Rice–wheat cropping systems in South Asia: issues, options and opportunities

The rice (Oryza sativa L.)–wheat (Triticum aestivum L.) cropping system is the largest agricultural production system worldwide, and is practised on 24 Mha in Asia. Many factors have threatened the long-term sustainability of conventional rice–wheat cropping systems, including degradation of soil health, water scarcity, labour/energy crises, nutrient imbalances, low soil organic matter contents, complex weed and insect flora, the emergence of herbicide-resistant weeds, and greenhouse-gas emissions. Options for improving the yield and sustainability of the rice–wheat cropping system include the use of resource-conservation technologies such as no-till wheat, laser-assisted land levelling, and direct-seeded aerobic rice. However, these technologies are site- and situation-specific; for example, direct-seeded aerobic rice is successful on heavy-textured soils but not sandy soils. Other useful strategies include seed priming, carbon trading and payment, the inclusion of legumes, and eco-friendly and biological methods of weed control. Irrigation based on soil matric potential using tensiometers can be useful for saving surplus water in direct-seeded, aerobic rice. These options and strategies will contribute to resolving water scarcity, saving labour and energy resources, reducing greenhouse-gas emissions, increasing soil organic matter contents, and improving the soil-quality index. Seed priming with various substances that supplement osmotic pressure (osmotica) is a viable option for addressing poor stand establishment in conservation rice–wheat cropping systems and for increasing crop yields. To strengthen the campaign for using resource-conservation technologies in rice–wheat cropping systems, carbon-payment schemes could be introduced and machinery should be offered at affordable prices. The persistent issue of burning crop residues could be resolved by incorporating these residues into biogas/ethanol and biochar production. Because rice and wheat are staple foods in South Asia, agronomic biofortification is a useful option for enhancing micronutrient contents in grains to help to reduce malnutrition.

Optimal rate and schedule of nitrogen fertilizer application for enhanced yield and nitrogen use efficiency in dry-seeded rice in north-western India

ABSTRACTDry direct-seeded aerobic rice (DSR) is an emerging attractive alternative to traditional puddled transplanted rice (PTR) production system for reducing labour and irrigation water requirements in the Indo-Gangetic plains (IGP) of India. The fertilizer N requirement of DSR grown with alternate wetting and drying water management may differ from that of PTR grown under continuous flooding due to differences in N dynamics in the soil/water system and crop growth patterns. Limited studies have been conducted on optimizing N management and application schedule for enhanced N use efficiency in DSR. Therefore, field experiments were conducted over 3 years in NW India to evaluate the effects of N rate and timing of its application on crop performance and N use efficiency. Interaction effects of four N rates (0, 120, 150, and 180 kg ha−1) as urea and four schedules of N application on yield and N use efficiency were evaluated in DSR. The N schedules included N application in three equal split doses (0, 35 and 63, and 14, 35 and 63 days after sowing, DAS) and four equal split doses (0, 28, 49 and 70; 14, 28, 49 and 70 DAS). There was no significant interaction between N rate and schedules on grain yield. Significant response to fertilizer N was observed at 120 kg N ha−1 and economic optimum dose for three equal split doses and skipping N at sowing was 130 kg N ha−1. Highest mean grain yield of 6.60 t ha−1 was obtained when N was applied in three equal split doses at 14, 35 and 63 DAS which was about 8.5% higher compared with N applied in four equal split doses at 14, 28, 49 and 70 DAS. Under the best N application schedule, agronomic N use efficiency (26 kg grain kg−1), recovery efficiency (49%) and physiological efficiency (53 kg kg−1) were comparable to the values reported in Asia for PTR. Results from our study will help to achieve high yields and N use efficiency in DSR to replace resource intensive PTR.

Comparison of conventional and conservation rice-wheat systems in Punjab, Pakistan

Adoption of resource conservation technologies such as direct seeded aerobic rice (DSAR) and no-till wheat (NTW) seems to be a farmer and ecofriendly option to sustain the productivity of rice (Oryza sativa L.)–wheat (Triticum aestivum L.) cropping systems (RWCS) on long term basis. This study was conducted to evaluate the impact of conventional and conservation rice-wheat cropping systems on soil properties, grain yield, and water/system productivities established at two experimental sites (Nankana Sahib and Sheikhupura). There were two rice production systems viz. DSAR, and puddled transplanted flooded rice (PudTR). After rice harvest, wheat was planted after plough tillage (PTW) or through no-till. The study was repeated over time and space. At both sites, higher total nitrogen (N), soil organic carbon (SOC), soil microbial biomass carbon (MBC) and soil microbial biomass nitrogen (MBN) were recorded in DSAR than PudTR. The DSAR yielded 3.8Mgha−1, against 3.6Mgha−1 in PudTR at Sheikhupura, while the similar paddy yield of 4.2Mgha−1 was harvested in DSAR and PudTR at Nankana Sahib. Overall, the adoption of DSAR saved 19% water compared with PudTR. Net benefits of US $729 and 601ha−1 were obtained from DSAR, against US $604 and 403ha−1 in PudTR, at Nankana Sahib and Sheikhupura, respectively. The highest water productivity of 3.01 and 3.43kgha−1mm−1 was recorded in DSAR compared to 2.41 and 2.50kgha−1mm−1 in PudTR at Nankana Sahib and Sheikhupura, respectively. The performance of wheat was better when grown after DSAR than PudTR for both experimental sites during both years. The higher total N (0.32gkg−1), SOC (3.75gkg−1), soil MBC (165μgg−1) and soil MBN (611.4μgg−1) were recorded for DSAR-NTW at both sites. The system productivity (output: input ratio) was 1.89 for DSAR-PTW at Nankana Sahib, and 1.87 for DSAR-NTW at Sheikhupura. In conclusion, DSAR followed by NTW was the best resource conservation technology to sustain the productivity of RWCS, and improve the net profit and the soil properties.

Influence of Sesbania Brown Manuring and Rice Residue Mulch on Soil Health, Weeds and System Productivity of Conservation Rice–Wheat Systems

AbstractThe sustainability of rice–wheat cropping system (RWCS) is threatened by increasing labor, water, and energy crises in the region. Conservation RWCSs offers an ecofriendly alternate option. This study was aimed to evaluate the impact of sesbania brown manuring in direct‐seeded aerobic rice (DSAR) and of rice residue mulch in no‐tilled wheat (NTW) on soil health, weed dynamics and system productivity. The experiment was composed of five RWCS systems: (i) DSAR‐NTW; (ii) DSAR + sesbania brown manuring‐NTW; (iii) DSAR‐NTW + rice residue mulch; (iv) puddled transplanted flooded rice (PudTR)‐NTW; and (v) PudTR‐plow‐tilled wheat. Sesbania brown manuring in direct‐seeded rice decreased the weed density and dry biomass 41–56% and 62–75%, respectively, than the sole direct‐seeded rice crop. At rice harvest, better soil health, in terms of total nitrogen (N), soil organic carbon, soil microbial biomass carbon, and soil microbial biomass nitrogen, was noted with DSAR + sesbania brown manuring‐NTW. Rice residue mulch retention in NTW decreased weed density and dry weight by 60 and 69%, respectively, than those under NTW with no mulch. At wheat harvest, highest total N, soil organic carbon, and soil microbial biomass carbon were recorded with DSAR‐NTW + rice residue mulch, followed by DSAR + sesbania brown manuring‐NTW. Overall, NTW grown after DSAR + sesbania brown manuring produced more grain yield than PudTR‐NTW and PudTR‐plow‐tilled wheat systems. In conclusion, sesbania brown manuring in DSAR and residue mulch retention in NTW may be opted to improve soil properties, suppress weeds, and to harvest better grain yield and achieve higher system productivity in conservation RWCSs. Copyright © 2016 John Wiley & Sons, Ltd.

Crop establishment method and irrigation schedule effect on water productivity, quality, economics and energetics of aerobic direct-seeded rice (Oryza sativa L.)

Rice is cultivated through transplanting of seedling in submerged field which is a cumbersome, labour intensive and water-guzzling practice. A field experiment was conducted to study the effect of crop establishment methods and irrigation schedules on water productivity, economics and energetics of aerobic direct-seeded rice at Punjab Agricultural University, Ludhiana, India, during Kharif 2012–2013. The experiment was laid out in split plot design, keeping combinations of two tillage system (no-tillage and conventional tillage) and two methods of sowing (uni-directional and bi-directional) in main plots and four irrigation schedule [(30, 45, 60 and 75 mm CPE (cumulative pan evaporation)] in sub plots. Aerobic direct-seeded rice sown after conventional tillage gave significantly higher grain yield than no-till with 15.4 % higher water expense efficiency. The energy gain and net monetary returns were 13.2 and 21.2 % higher in conventional sown crop than no-till, respectively. Bi-directional sowing resulted in 26.5 % higher grain yield than uni-directional with no effect on quality traits of grains. The net energy gain and net monetary returns were 26.5 thousands MJ/ha and 125.3 $/ha higher from bi-directional sown crop than uni-directional sown crop. Crop irrigated at 30 mm CPE schedule resulted in significantly higher grain yield than that irrigated at 45, 60 and 75 mm CPE. The energy gain, energy use efficiency and net returns were also maximum at 30 CPE schedule than at 45, 60 or 75 CPE. However, brown, milled and head rice recoveries were statistically at par between irrigation scheduling at 30 and 45 mm CPE but significantly better than 60 and 75 mm CPE. Bi-directional sowing with conventional tillage and irrigation at 30 CPE is an energy efficient and economical viable technique for direct-seeded rice.

Nitrogen and weed management in direct-seeded aerobic rice

Nitrogen and weed management in direct-seeded aerobic rice

Efficacy and economics of weed management strategies in aerobic rice (Oryza sativaL.)

Aerobic rice is a new concept of rice (Oryza sativa L.) cultivation to decrease water requirements in rice. Weeds are perceived to be the most severe constraint to the direct-seeded aerobic rice as compared to transplanted rice. The investigation was undertaken, primarily to identify the most suitable method for managing weed problem in aerobic rice during summer 2013 at College of Agriculture, Vellayani. Weeds resulted in 45.46% reduction in grain yield of rice under aerobic condition. Broadleaved weeds were the most dominant group followed by sedges and grasses. Preemergence application of oxyfluorfen @ 0.15 kg a.i ha−1 + one hand weeding at 20 DAS recorded the highest weed control efficiency (89.43%), higher grain yield (3500 kg ha−1), net income ( 31967 ha−1) and benefit: cost ratio (1.62). The grain yield recorded by this treatment remained at par with hand weeding (3889 kg ha−1). The net income and benefit: cost ratio were 44.6 and 22.7% higher than hand weeding, respectively.

Potentially toxic elements concentration in milled rice differ among various planting patterns

Soil contamination with potentially toxic elements (PTEs) due to rapid development of industry and agriculture has threatened the food security. Rice, the staple food of more than half of the world's population is thought as the prominent source for intake of PTEs by human beings. In present study, we compared different rice planting patterns, viz., dry direct-seeded aerobic rice (DSA), dry direct-seeded flooded rice (DSF) and transplanted-flooded rice (TFR) regarding PTEs (Mn, Co, Ni, Cu, Zn, Mo, Cd and As) concentration in milled rice and milled rice yield. Two inbred (Lvhan1, Huanghuazhan) and two hybrid (Hanyou3, Yangliangyou6) cultivars were used in present study. We found that Mn, Co, Ni, Cu, Zn and Cd concentrations in milled rice under DSF were lower than that in DSA, and were comparable with that under TFR. Furthermore, Mo and As in milled rice under DSF were lower than that under TFR and a little higher than DSA. Our results also depicted that on average, there were no significant differences in milled rice yield among various planting patterns across cultivars and years. None of the PTE exceeded the critical limits for milled rice except Cd in DSA and As in TFR. Along with the benefits of higher resource use efficiency and less labor requirement; comparable yield with TFR and moderate PTEs accumulation indicated that DSF is a more suitable planting pattern in the context of environmental sustainability. Cultivar variations were also apparent regarding PTEs concentration in milled rice and milled rice yield, which suggested that future studies should focus on breeding/selection of high yielding cultivars with low PTEs accumulation.

Comparison of Morpho-physiological Traits and Yield Attributes in Direct-seeded Aerobic and Conventional Transplanted Rice

Water stress is one of the main environmental stresses responsible for reducing crop productivity. Vital biochemical processes including photosynthesis, respiration, protein synthesis and assimilation of organic nitrogen have been demonstrated to be adversely affected by water stress. Traditionally, rice is grown by transplanting 3-to-5 week old seedlings into puddled fields. But in recent years, direct-seeded aerobic cultivation is being adopted by farmers because of its water saving potential. However, lower grain yield has been recorded in direct-seeded aerobic rice as compared with conventional transplanted crop. The susceptibility of rice crop to water stress varies with the variety, degree, duration of stress and its coincidence with different growth stages. The adverse effect of rice to water stress is more pronounced at reproductive stage and leads to a reduction in yield and yield attributes. Irrigation management strategies under direct-seeded aerobic condition can be developed to reverse the yield decline only after the causes of yield decline are identified. This article reviews the physiological and biochemical basis of yield gaps between rice crop grown under direct-seeded aerobic and conventional transplanted conditions.

Yield of aerobic rice affected by high temperature stress during summer season -A study from red and laterite zone of West Bengal, India

Field experiment on the performance of aerobic direct seeded rice (ADSR) under red and laterite zone of West Bengal was conducted at Rice Research Station, Bankura, West Bengal, India during summer season, 2012. The experimental soil was sandy loam with acidic in nature (pH: 5.2). The results exhibited that the grain yield (1 t ha-1) of rice in aerobic situation was low. This might be due to high atmospheric temperature during flowering period, which results in poor grain setting in panicle and most of them became chaffy due to spikelet sterility. Ultimately, it produced low grain yield of rice in aerobic situation during summer season due to high temperature at flowering period, grain formation and grain ripening stages. Thus, aerobic rice system of cultivation needed good management practices.

Performance and Water-use Efficiency of Rice Relative to Establishment Methods in Northwestern Indo-Gangetic Plains

Gains or losses in grain yield and water-use efficiency of aerobic direct-seeded rice (Oryza sativa L.) must be considered before promoting this technology in areas where this is not common. In the northwestern Indo-Gangetic Plains (IGP) of South Asia, irrigation water for rice production is becoming scarce because of depleting surface and groundwater resources. The objective of this study was to compare the crop performance and water-use efficiency of 10 selected rice cultivars between aerobic direct-seeded rice (ADSR) and conventional puddled transplanted rice (CPTR) on a sandy loam soil in Punjab Agricultural University (PAU), Ludhiana, India. Grain yields were similar between ADSR and CPTR for cultivars PR-120, Punjab Mehak 1, Fang-ai-zan, and RH-664. Grain yields of the other cultivars decreased significantly in ADSR compared with CPTR. PAU-201, a medium-duration cultivar, had the highest grain yields in each crop establishment method, followed by PR-120. Water-use efficiency (WUE) values for Fang-ai-zan, RH-257 (hybrid), PAU-201, and PR-120 were significantly higher than the WUE of any other cultivar, and they also had high values for stress-tolerance index (STI). Averaged across cultivars, WUE was similar in ADSR and CPTR as yield reduction in ADSR overweighed the benefit of water saving. We recommend that for more economic water use in the northwestern part of IGP, growing cultivars such as Fang-ai-zan, RH-257, PR-120, and PAU-201 in ADSR because of their lower water requirement, yield maintenance, and relatively higher STI. Correlation coefficients between STIs revealed that STI, mean productivity (MP), and geometric mean productivity (GMP) were the best criteria for the selection of high-yielding cultivars under ADSR and CPTR.

Optimizing Seed Rate to Suppress Weeds and to Increase Yield in Aerobic Direct-seeded Rice in Northwestern Indo-Gangetic Plains

Weed infestation is a major constraint to widespread adoption of aerobic, direct-seeded rice (Oryza sativa L.). Higher than optimum initial seeding density for obtaining more panicles/m2 is often accompanied by reduced panicle size and 1,000-grain weight, and high rate of spikelet sterility. On the other hand, weeds in plots with a lower seeding rate have a better chance to emerge, grow and build up a strong population and thus pose a serious crop-weed competition. Experiments were conducted during kharif (rainy season) 2008 and 2009 to determine the optimum seed rate that can substantially reduce rice-yield loss caused by weed competition under aerobic conditions. A factorial-treatment arrangement was used with factors consisting of five seed rates (15, 30, 60, 120, and 240 kg/ha) and two weed-pressure treatments (weedy-check and weed-free). Weed pressure caused a significant reduction in yield; there was up to 36.2% reduction in yield for weedy check as compared with the weed-free treatment. Seeding rat...

Weed Management in Aerobic Rice in Northwestern Indo-Gangetic Plains

Aerobic rice systems, wherein the crop is established via direct seeding in non-puddled, non-flooded fields, are among the most promising approaches for saving water and labor. However, aerobic systems are subject to much higher weed pressure than conventionally puddled transplanted rice (CPTR). Experiments were conducted for two years to develop effective and economical methods for managing weeds in aerobic rice grown by direct seeding rather than by conventional transplanting method. The proportion of mean grass-weed dry matter was 28.3% more in aerobic direct-seeded rice (ADSR) as compared to CPTR. Both weed density and dry weight were negatively correlated with rice grain yield. ADSR treatment produced yield similar to CPTR treatment when weeds were controlled effectively. Post-emergence application of bispyribac Na 25 g/ha and penoxsulam 25 g/ha could effectively control all the weeds in ADSR. Irrigation water productivity remained statistically the same in both ADSR and CPTR under the weed-free situation or when bispyribac Na herbicide was applied as post-emergence because of effective weed control in ADSR. The variation in net profitability between the ADSR and CPTR decreased with herbicide treatments, viz., Bispyribac Na, followed by penoxsulam and sequential application of pretilachlor and metsulfuron.

Weed management in aerobic rice systems under varying establishment methods

Aerobic rice systems, wherein the crop is established via direct-seeding in non-puddled, non-flooded fields, are among the most promising approaches for saving water and labour. However, aerobic systems are subject to much higher weed pressure than conventionally puddled transplanted rice (CPTR). Experiments were conducted for 2 years to develop effective and economical methods for managing weeds in aerobic rice grown by direct-seeding or transplanting on flat land or furrow-irrigated raised-bed systems (FIRBS). Total weed dry weight and weed density were lower with CPTR and highest with aerobic direct-seeded rice on a FIRBS (ADSB), followed by aerobic direct-seeded rice (ADSR). In terms of weight grassy weed constituted 78–96% of total weed weight in all systems of rice establishment. Loss of grain yield of rice due to weed competition ranged from 38% to 92%, being the highest in ADSB. Both weed density and dry weight were negatively correlated with rice grain yield. ADSR treatment produced yield and net economic returns similar to CPTR treatment when weeds were controlled. Pretilachlor with safener at 500 g a.i. ha −1 applied 3 days after sowing (DAS)/ days after transplanting (DAT) followed by chlorimuron+metsulfuron at 4 g a.i. ha −1 applied 21 DAS/DAT followed by hand-weeding at 35 DAS/DAT could effectively control all the weeds. The next best treatment was cyhalofop-butyl at 120 g a.i. ha −1 applied 14 DAS/DAT followed by chlorimuron+metsulfuron at 4 g a.i. ha −1 applied 21 DAS/DAT followed by hand-weeding at 35 DAS/DAT. The ADSR was as effective as conventionally puddle-transplanted rice in attaining higher rice grain yield and net returns when weeds were kept under control.

Stand establishment techniques of rice in conjunction with nutrient sources for soil health and productivity of rice (Oryza sativa)wheat (Triticum aestivum) cropping system

A field experiment was conducted during 201012 at Pantnagar, Uttarakhand, to study the effect of varying nu- trient sources and methods of rice (Oryza sativa L.) cultivation on the growth, yield attributes, productivity, eco- nomics of rice and soil fertility and its carry-over effect on wheat [Triticum aestivum (L.) emend. Fiori & Paol.]. The treatment comprised 3 rice-establishment methods, viz. conventional transplanting (CT), system of rice intensifica- tion (SRI) and direct-seeded aerobic rice (DSR) in main-plots, and 4 nutrient sources, viz. N +N 25(FYM) 95(urea), N +N N +N and N , in sub-plots, with 4 replications. Significantly higher number of panicles/ 50(FYM) 70(urea), 75(FYM) 45(urea) 120(urea) m2, leaf-area index (LAI), chlorophyll content of leaf, root dry weight and panicle weight of rice were obtained with system of rice intensification (SRI) compared to conventional transplanting and aerobic methods of cultivation. This method also recorded significantly higher grain yield (5.49 t/ha, pooled over 2 years), being 11% higher than conventional transplanting. The lowest grain yield (4.63 t/ha, pooled over 2 years) was recorded under direct- seeded aerobic rice, being 7% lower than conventional transplanting. System of rice intensification, among 3 rice establishment methods was more advantageous in terms of net return (23%) and grain yield (11%) than conven- tional transplanting. The total productivity (pooled over 2 years) was also higher (9.44t/ha,) under system of rice intensification (SRI) treatment. Among the nutrient sources, N + N produced higher number of panicles/ 75 (FYM) 45 (urea) m2, leaf-area index (LAI), chlorophyll content of leaf, root dry weight, root volume, panicle weight and pooled (over 2 years) grain yield of rice (5.17 t/ha) and wheat (3.77 t/ha). The higher net monetary returns ( 41,450/ha average of 2 years) as well as benefit: cost ratio (1.59; average of 2 years) of the system was also observed under this treatment. N (FYM) + N (urea) kg/ha was found best in improving the yield and yield attributes of wheat after 75 45 rice.