Dry Direct-seeded Rice Research Articles

Effect of tillage and crop establishment, residue management and K fertilization on yield, K use efficiency and apparent K balance under rice-maize system in north-western India

The rice-maize cropping system (RMS) is an emerging option for diversification of the prevalent rice-wheat system (RWS) in South Asia. Studies underlined the significance of adequate potassium (K) nutrition for sustainable intensification of the RMS. Although studies on combined effects of tillage, residue retention, and nutrient management on crop yields and nutrient use efficiency for the RWS are plenty, such studies are scarce for the RMS. We, therefore, conducted a 5-year field study on sandy loam (Typic Ustochrept) soil at Modipuram, India to evaluate the effects of tillage and crop establishment, residue management and K fertilization on crop productivity, K use efficiencies, changes in soil K status, and apparent K balance under irrigated RMS in north-western India. Three combinations of tillage and crop establishment methods i.e., puddled transplanted rice (TPR) followed by conventional-till maize (TPR/CTM); conventional-till dry direct-seeded rice (CTDSR) followed by CTM (CTDSR/CTM); and zero-till DSR followed by zero-till maize (ZTDSR/ZTM) were considered as main plots. Sub-plot treatments consisted of two residue management options i.e., removal of residues (-R) of both crops, and partial residue retention (5 Mg ha−1) for rice and maize, either at soil surface in zero till (ZT) plots or incorporated into the soil in conventionally-till (CT) plots (+R). The sub-sub plot treatments were no-K application (-K) and 62 kg K ha−1 application (+K) to both rice and maize. Data summed-up for 5 years revealed that rice grain yield and K uptake under TPR were significantly higher (p < 0.05) compared with CT/ZT DSR, irrespective of residue and K management options. The maize yield and K uptake were highest under the ZTDSR/ZTM treatment. Both rice and maize yields were significantly (p < 0.05) higher with 62 kg ha−1 K application under −R plots, but such effects were not significant under + R plots. Similarly the effect of residue management on yield and K uptake of rice and maize was significant only in the absence of fertilizer K application. Recycling of rice residue in maize had more pronounced effect on K uptake compared with that of maize residue in rice. Agronomic and recovery efficiencies of applied K were lower under +R plots, and agronomic efficiency was further decreased when both rice and maize were grown under ZT conditions (ZTDSR/ZTM). Soil exchangeable K content at 0–0.05 m and 0.05–0.15 m depths was significantly higher (p < 0.05) under ZTDSR/ZTM compared with that under CTDSR/CTM and TPR/CTM treatments, and the values were greater under +R + K compared with −R−K treatments. Soil exchangeable K under −K−R plots dropped to 102 and 90 mg kg−1 at 0–0.05 m and 0.05–0.15 m depth, respectively vis–a-vis the initial K content (122 and 114 mg kg−1, respectively). The apparent K balance, computed as K addition less K off-take by rice and maize during the study period of 5 years, was invariably negative in the absence of K fertilizer i.e., −307 kg ha−1 in TPR/CTM (+R−K) to −1483 kg ha−1 in ZTDSR/ZTM (−R−K) treatments. On contrary, the apparent K balance was positive in +R + K plots under different tillage and crop establishment methods. Positive correlation between soil exchangeable K and K input indicated that soil K mining in the RMS could be mitigated to a great extent with adequate supply of K through residue retention and K fertilization.

PERFORMANCE OF AUS RICE IN DIFFERENT TILLAGE SYSTEMS AND CROP ESTABLISHMENT METHOD IN SOUTHWEST BANGLADESH

High labor wage and irrigation water scarcity are the major constraints to becoming rice production less profitable and unsustainable in Bangladesh. To address these problems, rice production needed less water and less labor consuming production technologies. In traditional rice production systems which is puddled-transplanted rice (PTR), a significant amount of water and labor are used for tillage (wet) and transplanting operations. A farmers’ participatory on-farm trial was conducted to evaluate the performance of aus rice at different tillage systems and crop establishment methods in the southern part of Bangladesh. Wet tillage (puddled systems) to dry-tillage and transplanted rice to direct dry-seeded rice (DSR) may have the potential to reduce production cost by using less labor and water, resulting in higher profit. The trial examined tillage systems (strip tillage, reduced tillage and puddling) and crop establishment methods (direct dry-seeded and transplanted) in six farmers’ fields in aus 2015. Crop established by reduced-and strip-tillage in DSR conditions reduced crop duration by 7 d compared to PTR. Grain yield (4.4-4.6 t ha-1) was similar in DSR which is established by reduced-and strip-tillage conditions and PTR; however, total production cost in DSR was 15-18% lower than the PTR. Slightly higher but significantly similar gross income was recorded in PTR than DSR, however, net profit was significantly lower in PTR and it was due to higher production cost involvement. DSR has the potentiality of similar yield to PTR and reduces production cost which increases the net profit of rice production.

Planting methods and weed management to improve yield in dry-seeded rice

A field experiment was conducted to evaluate the effect of planting methods and weed management in direct dry-seeded rice during summer season of 2012 and 2013 at Agricultural Research Farm, Institute of Agricultural Sciences Banaras Hindu University, Varanasi (Uttar Pradesh). The treatment comprised of five rice planting treatments, viz. conventional tillage normal spacing [row to row (R x R)-18 cm], conventional tillage square planting (RxR-20 cm, plant to plant (P x P)-20 cm), conventional tillage paired row (9-27-9 cm), reduced tillage paired row (9-27-9 cm), reduced tillage square planting (R x R-20 cm, PxP-20 cm) in main plot and sub-plot consisted of four weed management treatments, viz. weedy, two hand weeding, pendimethalin 1.0 kg/ha fb azimsulfuron 17.5 g/ha + bispyribac 25 g/ha (tank mixed) at 15 DAS fb one hand weeding (HW), oxadiargyl 50 g/ha fb metsulfuron-methyl 2 g/ha + chlorimuron-ethyl 2 g/ha (ready mix) at 20 DAS fb 1 HW. Significant reduction in weed density and biomass was recorded in two hand weeding fb pendimethalin 1.0 kg/ha fb azimsulfuron 17.5 g/ha + bispyribac 25 g/ha (tank mixed) at 15 DAS fb 1 HW which resulted in improved growth and yield attributes and yield of rice. Amongst rice planting methods, conventional tillage normal spacing (R x R-18 cm) and conventional tillage paired row (9-27-9 cm) were able to compete with weeds more as compared to other rice planting methods resulting in lower weed density and weed biomass, enhanced rice growth and yield attributing characters and yield.

Soil biochemical changes at different wheat growth stages in response to conservation agriculture practices in a rice-wheat system of north-western India

Intensive tillage, removal or burning of crop residues, limited organic manure use, declining irrigation water resources and scarcity of labour are the major causes of soil degradation and unsustainability of rice (Oryza sativa L.)–wheat (Triticum aestivum L.) system (RWS) in South Asia.Resource conservation technologies (RCTs) such as zero tillage (ZT), dry direct seeded rice (DSR) and crop residues retained as mulch have shown promise to increase the productivity and profitability of RWS in South Asia. Effects of RCTs on soil biological parameters are unclear and contradictory. We evaluated the effects of conservation agriculture practices on changes in soil biochemical properties at different growth stages of wheat grown as the fifth crop in RWS. Twelve treatment combinations of tillage, crop establishment and crop residue management included four main plot treatments in rice: (1) conventional tillage (CT)-DSR,(2) ZT-DSR, (3) DTR, ZT machine transplanted rice and (4) PTR, conventional puddled transplanted rice. The three subplot treatments were: (i) CTW-R, CT wheat with both rice and wheat residues removed, (ii) ZTW-R, ZT wheat with residues of both the crops removed and (iii) ZTW+R, ZT wheat with rice residue retained as surface mulch in subsequent wheat. Irrespective of rice establishment methods, mean wheat grain yield under ZTW+R was 6% and 10% greater than CTW-R and ZTW-R respectively. Soil enzyme activities increased (5–18%) under ZTW+R compared with ZTW-R and CTW-R at different growth stages of wheat. The residual effect of rice establishment methods was significant on soil enzyme activities during wheat cropping, which were highest under ZT-DSR followed by CT-DSR, DTR and PTR. Soil organic carbon content in the 0–7.5 cm layer was significantly higher (7–9%) under the ZTW+R treatment compared with all the other treatments. Principal component analysis (PCA) identified three enzyme activities (dehydrogenase, fluorescein diacetate and phosphatase), and soil organic carbon content as the most sensitive indicators for assessing soil quality for RWS based on conservation agriculture. The PCA discriminated rice establishment systems with rice residue as surface mulch from rice establishment systems without rice residue and the maximum tillering stage from the other stages of wheat. The present study provided reliable biochemical indicators to monitor soil biological quality changes in response to conservation agriculture practices in RWS.

Influence of crop geometry and cultivars on growth, yield and production efficiency of dry direct-seeded rice (Oryza sativa L.)

A field experiment was conducted during kharif (summer) season of 2014, aim of the experiment was to investigate suitable crop geometry and cultivar and their influences on performance of dry direct-seeded rice (Oryza sativa L.), experimental treatments were consisting of 15 treatments, namely, main plots: five cultivars (MTU 7029, NDR 97, HUR 105, HUR 4-3 and PRH-10) and sub-plots: three crop geometry’s (20 x 10, 20 x 20 and 25 x 25 cm2). All the data recorded were statistically analyzed using the standard procedures of split-plot design. The results indicated that amongst cultivars, aromatic rice hybrid PRH-10 recorded significantly more grain yield (5582.32 kg/ha) than cultivar HUR 4-3 (4612.99 kg/ha) and NDR 97 (3397.82 kg/ha), whereas; it was statistically comparable with cultivar MTU 7029 (5489.24 kg/ha) and HUR 105 (5022.03 kg/ha). The cultivar PRH-10 also registered higher gross return (105771.9 `/ha), net return (66389.08 `/ha) and production efficiency (592.76 `/ha/day) than the remaining cultivars. The higher grain yield of PRH-10 over these cultivars was due to considerable improvement in most of its yield attributing characters like panicle length (27.92 cm), a number of grains/panicle (178.70) and test weight (26.35 g). In a case of crop geometry treatment, plant spacing of 25 x 25 cm2 recorded higher grain yield as compared to remaining plant spacing while the plant spacing of 20 x 10 cm2 recorded higher gross return, net return and production efficiency as compared to 20 x 20 and 25 x 25 cm2. Plant geometry plays an imperative role towards improving the grain yield of cultivars in direct seeded rice by optimal utilization of natural resources. Therefore, for getting higher net return and production efficiency, cultivar PRH-10 at plant spacing 20 x 10 cm2 can be raised in dry direct-seeded rice in Varanasi region of Eastern Uttar Pradesh.

Direct-seeded rice increases nitrogen runoff losses in southeastern China

recent years, alternative rice cultivation methods have been widely developed in Asia, and the environmental consequences of these practices on nitrogen (N) runoff losses from intensively cultivated rice fields deserve attention. A two-year field experiment (2013–2014) was conducted in a rice field in southeastern China to evaluate the N losses in runoff resulting from four rice cultivationmethods: (1) conventional, manually transplanted seedling rice (CTSR); (2) mechanically transplanted seedling rice (MTSR); (3) dry direct-seeded rice (DDSR); and (4) wet direct-seeded rice (WDSR). Runoff volumes; runoff concentrations of NH4+-N, NO3−-N, and total N (TN); N uptake; and grain yield were measured. The seasonal runoff volumes varied from 775 to 2397m3ha−1 in 2013 and 2014. Compared with CTSR, WDSR and DDSR significantly increased the total runoff volumes by 76% and 30%in 2013, and by 46% and 26% in 2014, respectively. The seasonal TN losses in runoff from the rice fields ranged from 1.99 to 10.18kgNha−1, accounting for 0.74–3.77% of the seasonal N input during the two years. In contrast with CTSR, WDSR increased TN losses by 169% in 2013 and by 143% in 2014, while DDSR increased TN losses by 31% in 2013 and by 84% in 2014. Direct-seeded rice significantly increased runoff N losses during the early growth period largely by increasing runoff volumes and/or the N concentrations in runoff water. The main forms of N lost in runoff were NH4+-N for CTSR, MTSR and WDSR and NO3−-N for DDSR. The grain yield, N uptake at mid-tillering and panicle initiation stages were similar in WDSR and DDSR and significantly lower than those under CTSR and MTSR. The results show that direct-seeded rice increased N runoff losses from intensively cultivated rice fields in southeastern China.

Effect of soil test based nutrient management approaches on growth and yield of dry direct seeded rice (DryDSR)

Effect of soil test based nutrient management approaches on growth and yield of dry direct seeded rice (DryDSR)

Molecular Mapping of QTLs Associated with Lodging Resistance in Dry Direct-Seeded Rice (Oryza sativa L.).

Dry direct-seeded rice (DSR) is an alternative crop establishment method with less water and labor requirement through mechanization. It provides better opportunities for a second crop during the cropping season and therefore, a feasible alternative system to transplanted lowland rice. However, lodging is one of the major constraints in attaining high yield in DSR. Identification of QTLs for lodging resistance and their subsequent use in improving varieties under DSR will be an efficient breeding strategy to address the problem. In order to map the QTLs associated with lodging resistance, a set of 253 BC3F4 lines derived from a backcross between Swarna and Moroberekan were evaluated in two consecutive years. A total of 12 QTLs associated with lodging resistance traits [culm length (qCL), culm diameter (qCD), and culm strength (qCS)] were mapped on chromosomes 1, 2, 6, and 7 using 193 polymorphic SNP markers. Two major and consistent effect QTLs, namely qCD1.1 (with R2 of 10%) and qCS1.1 (with R2 of 14%) on chromosome 1 with id1003559 being the peak SNP marker (flanking markers; id1001973-id1006772) were identified as a common genomic region associated with important lodging resistance traits. In silico analysis revealed the presence of Gibberellic Acid 3 beta-hydroxylase along with 34 other putative candidate genes in the marker interval region of id1001973-id1006772. The positive alleles for culm length, culm diameter, and culm strength were contributed by the upland adaptive parent Moroberekan. Our results identified significant positive correlation between lodging related traits (culm length diameter and strength) and grain yield under DSR, indicating the role of lodging resistant traits in grain yield improvement under DSR. Deployment of the identified alleles influencing the culm strength and culm diameter in marker assisted introgression program may facilitate the lodging resistance under DSR.

Screening of water-efficient rice genotypes for dry direct seeding in South Asia

ABSTRACTRice genotypes having high crop water productivity in dry direct-seeded rice (DDSR) need to be assessed while promoting labor- and water-saving technology. The objective of this study was to evaluate the ability of several selection indices to identify genotypes with high crop water productivity in DDSR. A set of 16 genotypes [13 recombinant inbred lines (RILs) and three genotypes as check for control] were evaluated under DDSR for two consecutive years (2013 and 2014) using two irrigation regimes [-10 kPa (non-stress) and -20 kPa (stress)]. Grain yield varied from 5.3 to 8.4 t ha-1 and 5.9 to 8.7 t ha-1 for irrigation regimes of -20 and -10 kPa, respectively. Yield reductions caused by water stress ranged from 2.9 to 25.1%; being lowest in RIL1649 and highest in hybrid SVH-127. The genotypes with high stress-tolerance index (STI), mean productivity (MP), geometric mean productivity (GMP) and harmonic mean productivity (HAR) were identified as the most productive genotypes for high crop water productivity in DDSR. The results implied that selection based on stress tolerance indices likes STI, MP, GMP and HAR was useful in identifying genotypes with high crop water productivity under DDSR and RIL 1649 and SVH-127 were identified as superior genotypes in this regard.

Influence of crop establishment methods on yield, economics and water productivity of rice cultivars under upland and lowland production ecologies of Eastern Indo-Gangetic Plains

A field study on assessment of crop establishment methods on yield, economics and water productivity of rice cultivars under upland and lowland production ecologies was conducted during wet seasons (June–November) of 2012 and 2013 in Eastern Indo-Gangetic Plains of India. The experiment was laid-out in a split-plot design (SPD) and replicated four times. The main-plot treatments included three crop establishment methods, viz. dry direct-seeded rice (DSR), system of rice intensification (SRI) and puddled transplanted rice (PTR). In sub-plots, five rice cultivars of different groups like aromatic (Improved Pusa Basmati 1 and Pusa Sugandh 5), inbreds (PNR 381 and Pusa 834) and hybrid (Arize 6444) were taken for their evaluations. These two sets of treatments were laid-out simultaneously in two production ecologies, upland and lowland during both years. In general, lowland ecology was found favourable for rice growth and yield and resulted in 13.2% higher grain yield as compared to upland ecology. Rice grown with SRI method produced 19.4 and 7.0% higher grain yield in 2012 and 20.6 and 7.1% higher in 2013, over DSR and PTR. However, PTR yielded 13.1 and 14.5% higher grain over DSR during 2012 and 2013, respectively. On an average, Arize 6444 produced 26.4, 26.9, 28.9 and 54.7% higher grain yield as compared to PS 5, P 834, PNR 381 and IPB1, respectively. Further, the interaction of production ecologies × crop establishment methods revealed that, in upland ecology, SRI recorded significantly higher grain yield as compared to PTR and DSR, but in lowland, grain yield resulting from SRI was similar to the yield obtained with PTR and significantly higher than DSR. The latter two methods (PTR and DSR) yielded alike in lowland ecology in both study years. The production ecologies × crop establishment methods × cultivars interaction on grain yield showed that the growing of Arize 6444 cultivar using SRI method in upland ecology resulted in the higher grain yield (8.87 t/ha). But the cost of production was also highest in SRI followed by PTR and DSR across production ecologies and cultivars. Cultivation of hybrid (Arize 6444) involved higher cost of production than all other cultivars. Irrespective of crop establishment methods and cultivars, gross returns, net returns and B:C ratio were significantly higher in lowland compared to upland ecology. Owing to higher grain yield, SRI method fetched significantly higher gross returns and net returns over PTR and DSR. Average increase in net return with Arize 6444 was 68.8, 41.0, 37.7 and 33.1% over IPB 1, PNR 381, P 834 and PS 5, respectively. There was a saving of 30.7% water in SRI and 19.9% in DSR over PTR under upland ecology. Similarly in lowland ecology, water saving of 30.2% was observed in SRI and 21.2% in DSR over PTR. Due to higher yield and saving on water, SRI returned significantly higher total water productivity (TWP) (5.9 kg/ha-mm) as compared to DSR (3.5 kg/ha-mm) and PTR (3.6 kg/ha-mm) under upland ecology. In lowland ecology, also SRI (6.2 kg/ha-mm) resulted in higher TWP as compared to other two methods. However, DSR gave significantly higher TWP as compared to PTR. Among cultivars, hybrid Arize 6444 recorded the highest TWP in both upland and lowland production ecologies across crop establishment methods. Hence, growing of hybrid Arize 6444 with SRI method can enhance rice productivity and water-use efficiency in lowland and upland production ecologies of Eastern Indo-Gangetic Plains and in other similar regions.

QTL Hotspots for Early Vigor and Related Traits under Dry Direct-Seeded System in Rice (Oryza sativa L.).

Strong seedling vigor is desirable trait in dry direct-seeded rice (DSR) for enhancing crop establishment and the ability to compete against weeds. A set of 253 BC3F4 lines derived from cross between Swarna and Moroberekan was phenotyped for early vigor (EV) and 8 related traits viz., early uniform emergence (EUE), shoot length (SHL), stem length (SL), shoot fresh weight (SFW), total fresh weight (TFW), shoot dry weight (SDW), total dry weight (TDW), and root dry weight (RDW). Composite interval mapping analysis using genotypic data from 194 SNP markers identified six genomic regions associated with traits on chromosomes 3, 4, 5, and 6 with phenotypic variance ranging from 2.5 to 18.6%. Among them 2 QTL regions; one on chr3 (id3001701-id300833) and the other on chr5 (wd5002636-id5001470) were identified as QTL hotspots A and B respectively and expressed consistently in field as well as glasshouse condition. The majority of QTLs identified for early vigor, and related traits were clustered in the QTL hotspots A (qEV3.1, qEUE3.1, qSHL3.1, qSL3.1, qSFW3.1, qTFW3.1, qRDW3.1) and QTL hotspot B (qEV5.1, qEUE5.1, qSHL5.1, qSL5.1, qSFW5.1, qSDW5.1, qTDW5.1). Ten putative candidate genes viz., 1-alpha-amylase precursor, 2-glutamate decarboxylase, 1-ethylene-insensitive 3, 3-expansin precursor, and 3-phenylalanine ammonia-lyase associated with the target traits were identified in the selected QTL regions. Mutations were identified in the coding region of alpha-amylase precursor and ethylene-insensitive 3 gene between the parents which can be utilized in marker assisted breeding. Trait relationships among the agro-physiological traits were examined to select the best genotypes for the given traits for use in future breeding programs.

Comparison of Weed Seedbanks in Different Rice Planting Systems

Core Ideas Weed seedbanks were compared in three rice planting systems: machine‐transplanted rice, water direct‐seeded rice, and dry direct‐seeded rice. Weed seedbanks were mainly distributed in soil within a depth of 10 cm. Dry direct‐seeded rice tended to maintain larger seedbanks of sedges, grasses, and some upland weeds. Water direct‐seeded rice contained the smallest weed seedbank overall. Machine‐transplanted rice had larger seedbanks of broadleaf weeds and some traditional rice weeds. Machine‐transplanted rice (Oryza sativa L.) (MTR), water direct‐seeded rice (WDSR), and dry direct‐seeded rice (DDSR) are three important alternatives to traditional manual transplantation of rice. Weed infestation is a pervasive problem in all rice planting systems. The weed seedbanks under different rice planting systems have seldom been compared. Thus, we sampled weed seeds in fields employing MTR, WDSR, and DDSR consecutively for at least 5 yr in Wujin County, eastern China. Seeds of 26 companion weed species of rice, comprising 16 families, were observed. Most weed seeds, 82.5% in MTR, 75.3% in WDSR, and 81.7% in DDSR, were distributed in soil 0‐ to 10‐cm deep. As soil depth increased, the seedbanks of total weeds, broadleaf weeds, grasses, and sedges all significantly decreased under the different rice planting systems, except for sedges under WDSR. The DDSR tended to maintain larger seedbanks of sedges and grasses, as well as some upland weeds, such as Digitaria sanguinalis (L.) Scop. and Eleusine indica Gaertn. The WDSR system contained the smallest weed seedbank overall but tended to have larger seedbanks of several weeds, such as Ammannia arenaria H. B. K. and Lindernia procumbens (Krock.) Philcox. Weedy rice and Cyperus difformis L. tended to maintain larger seedbanks in DSR fields. The MTR fields tended to have larger seedbanks of broadleaf weeds and some traditional rice weeds, with significantly lower richness of weed species in the seedbank. Therefore, to downsize the weed seedbank, WDSR or MTR should be employed rather than DDSR when possible. Moreover, the influences rotation of different rice planting systems on the weed seedbank merit more studies.

Physical and Chemical Properties of a Sandy Loam Soil Under Irrigated Rice-Wheat Sequence in the Indo-Gangetic Plains of South Asia

Resource conservation technologies (RCTs) such as zero tillage (ZT), dry direct seeded rice (DSR) and crop residues as mulch are known to increase productivity and profitability of rice-wheat system (RWS) in South Asia. There are, however, few studies on assessing the effect of RCTs on physical and chemical properties of soil under RWS. A field experiment on a sandy loam soil was conducted on RWS for two years at Modipuram, India involving six treatment combinations of three tillage and crop establishment methods in rice, (i) conventional puddled transplanted rice (CT-PTR), (ii) conventional dry tillage followed by direct seeding of rice (CT-DSR), and (iii) zero tillage followed by direct seeding of rice (ZT-DSR), and two green manuring options (with and without intercropping of Sesbania aculeata, -S or +S). In the succeeding wheat, rice residue (RR) was retained in sesbania green manure treatments and it was removed from no sesbania plots. Wheat was direct sown after ZT (DSW) in all the plots. Substituting PTR/ DSW without crop residues with ZT-DSR/DSW plus residue cycling reduced electrical conductivity from 0.146 dS mA¢Â€Â’1 to 0.128 dS mA¢Â€Â’1 and increased soil organic C from 5.72 g kg-1 to 6.25 g kg-1 in 0-15 cm layer. Similarly, water-stable aggregates (WSAs) >0.25 mm were 28% higher and their mean weight diameter increased by 11.9% in ZT-DSR/ DSW plus residues compared to PTR/DSW without crop residues plots. On average, there was a 23.6% increase in large (4.75-8.00 mm) aggregates and a reduction of 15.8% in finer (0.106A¢Â€Â’0.25 mm) aggregates in residue retention treatments over the no-residue treatments. In plots without puddling (ZT-DSR), the infiltration rates were higher (2.97-3.34 mmh-1) than in the CT-PTR (2.41-2.62 mmh-1). Residue retention compared to residue removal not only increased available K contents from 110.5 to 129.2 kg ha-1 but also showed favorable effects on soil matric potential and soil temperature during the wheat season. These beneficial effects on soil quality in just two years after introducing conservation tillage and residue management practices demonstrate potential to improve the long-term productivity and profitability of the RWS. However, the increased rate of infiltration under ZT with residue retention needs new irrigation techniques to minimize the loss of water through percolation during rice season.

Response of first flood irrigation timing after rice dry-direct-seeding: Productivity and greenhouse gas emissions in Central China

A major challenge in rice (Oryza sativa L.) production is to simultaneously achieve the goals of reducing water consumption, labor requirements and greenhouse gas (GHG) emissions while maintaining a sustainable grain yield. Dry direct-seeded rice (DDSR) has been proposed as an alternative rice production strategy because it reduces water consumption and labor requirements and increases system productivity. To evaluate the responses of grain yield, yield components, water productivity and GHG emissions to different first flood irrigation times under DDSR, field experiments were conducted under three different first-irrigation times: 15, 30 or 45days after sowing (DAS) in 2014 and 15, 35 or 55 DAS in 2015. The precipitation in the 45 DAS was 291mm in 2014 and 160mm in 2015. The results indicated that the grain yields under DDSR were not affected by the different flooding times in 2014 but were significantly reduced when the first flood irrigation time was prolonged to 55 DAS in 2015. Delaying the first flood irrigation time after sowing conserved water and significantly increased water productivity (WP) under DDSR. Prolonging the first flood irrigation time after sowing markedly decreased the CH4 gas emission, although delaying the first flood irrigation time increased the N2O gas emission, the global warming potential was significantly reduced. Based on these findings, we put forward the recommendation that the timing of first flood irrigation can be postponed to 45 DAS with precipitation levels higher than 160mm under DDSR in central China. However, long-term studies across different environments are inevitable to get definite conclusions.

Mitigation of greenhouse gas emission from rice–wheat system of the Indo-Gangetic plains: Through tillage, irrigation and fertilizer management

Rice–wheat cropping systems (RWCS) of the Indo-Gangetic plains (IGP) of India are tillage, water and energy intensive and an important source of greenhouse gas (GHG) emission. Developing agronomic management in RWCS that lead to minimum adverse impact on soil, enhances water use efficiency, reduces GHG emission and are climate resilient is required. The aim of this study was to evaluate different combinations of GHG mitigation technologies for rice and wheat and to find suitable low carbon options for RWCS in the IGP. Seven management systems i.e. conventionally tilled wheat (CTW); zero tilled wheat (ZTW); transplanted puddled rice (TPR); dry direct seeded rice (DSR); intermittent wetting and drying (IWD); application of neem oil coated urea (NOCU); and surface application of rice residue (RR) were experimented in six combination of rotations [CTW-TPR, ZTW-TPR, ZTW-IWD, ZTW-DSR, ZTW+RR-DSR and (ZTW-TPR)+NOCU] for two consecutive years. Among these rotations, ZTW-DSR and ZTW+RR-DSR showed the lowest global warming potential (GWP) and GHG intensity in both the years. Adoption of these systems in the Indian-IGP can reduce GWP of the conventional RWCS (CTW-TPR) by 44–47% without any significant loss in the system yield. This was mainly due to significantly low CH4 emission (82.3–87.2%) in DSR as compared to TPR due to prolonged aerobic condition under DSR. However, frequent wetting and drying in DSR led to higher denitrification emissions of N2O (60–70%). Significantly higher emissions of N2O were observed in ZTW treatments (8–11%). NOCU was found effective in reducing N2O emission from ZTW (17.8–20.5%) leading to lower GWP as compared to CTW. Application of rice residue in ZTW treatment also reduced N2O emission (11–12.8%). There was no significant effect of different treatments in rice on GHG emission from the succeeding wheat crop; however, ZTW and ZTW+RR were found to enhance CH4 emission from the succeeding rice treatments.

Lower global warming potential and higher yield of wet direct-seeded rice in Central China

Direct-seeded rice is a promising option because it saves water and labor, and it increases productivity. Nonetheless, few studies have evaluated the transition from traditionally transplanted rice to direct-seeded rice. Here we compared yield, water productivity, and greenhouse gas emissions of dry direct-seeded rice, wet direct-seeded rice, and transplanted rice in Central China in 2014 and 2015. We grew four rice cultivars: Huanghuazhan, LvdaoQ7, Yangliangyou6, and Yliangyou1. We measured grain yield, yield components, water consumption, water productivity, and greenhouse gas emissions. Our results show that the grain yield of wet direct-seeded rice was 10.8 % higher than that of transplanted rice, when averaged across cultivars and both years. Grain yield of dry direct-seeded rice and transplanted rice was similar. Water productivity of dry direct-seeded rice was 11.6 % higher than that of transplanted rice. Water productivity of wet direct-seeded rice was 13.4 % higher than that of transplanted rice. Global warming potential was 76.2 % lower for dry direct-seeded rice and 60.4 % lower for wet direct-seeded rice than for transplanted rice. Wet direct-seeded rice was found to be more susceptible to lodging than dry direct-seeded rice and transplanted rice. Overall, wet direct-seeded rice is the best system for Central China due to higher grain yield and water productivity and lower global warming potential. Dry direct-seeded rice may also be suitable for some regions where water is scarce for soil puddling during land preparation.

Economic Analysis of Different Greenhouse Gas Mitigation Technologies in Rice-Wheat Cropping System of the Indo-Gangetic Plains

To reduce the greenhouse gas (GHG) emission from rice and wheat cultivation several mitigation options have been suggested. However, economic impact of these technologies has been poorly documented. In the present study economic analysis of some emerging GHG mitigation technologies for rice-wheat system of the Indo-Gangetic Plains has been carried out. The experiment consisted of six combinations of wheat- rice crop rotation using eight treatments, including conventionally tilled wheat (CTW), zero tilled wheat (ZTW), transplanted puddled rice (TPR), dry direct seeded rice (DSR), intermittent wetting and drying (IWD), application of rice straw (RS) with ZTW and use of neem oil-coated urea (NOCU) in TPR and ZTW. Cost of various inputs and income from grain and straw were used for computing the benefit to cost (B : C) ratio in the different treatments. ZTW showed higher yield and B : C ratio compared to CTW along with reduction in fuel consumption during tillage operation. In spite of lower yield under DSR and IWD, saving of water, labour and energy in these treatments lowered the cost of cultivation and enhanced B : C ratio similar to TPR. Application of rice straw and NOCU also showed positive impact on crop yield. B : C ratio of rice-wheat system ranged from 1.62 to 1.86 in the first year and from 1.86 to 2.16 in the second year. B : C ratio was significantly higher in all the treatments in the experimented rice-wheat system compared to conventional system, i.e. CTW-TPR. The ZTW + RR - DSR (WR5) showed highest B : C ratio followed by ZTW + DSR (WR4) in both the seasons.

Herbicide options for effective weed management in dry direct-seeded rice under scented rice-wheat rotation of western Indo-Gangetic Plains

Farmers' participatory field trials were conducted at Madhuban, and Taraori, the two participatory experimental sites/locations of the Cereal Systems Initiative for South Asia (CSISA), a collaborative project of IRRI and CIMMYT in Karnal district of Haryana, India, during Kharif (wet season) 2010 and 2011. This research aimed to evaluate preemergence (PRE) and postemergence (POST) herbicides for providing feasible and economically viable weed management options to farmers for predominant scented rice varieties. Treatments with pendimethalin PRE fb bispyribac-sodium + azimsulfuron POST had lower weed biomass at 45 days after sowing (DAS). At Madhuban, highest grain yield of scented basmati rice (3.43 t ha−1) was recorded with the sequential application of pendimethalin PRE fb bispyribac-sodium + azimsulfuron POST. However, at Taraori, yields were similar with pendimethalin or oxadiargyl PRE fb bispyribac-sodium and/or azimsulfuron POST. Applying oxadiargyl by mixing with sand onto flooded field was less effective than spray applications in non-flooded field. The benefit-cost ratio of rice crop was higher with herbicide treatments at both sites as compared with the non-treated weed-free check except single PRE and POST applications and sequential application of oxadiargyl PRE fb oxadiargyl PRE. In a separate experiment conducted at Nagla and Taraori sites, scented rice cultivars' ('CSR 30′ and 'Pusa 1121′) tolerance to three rates of azimsulfuron (15, 25, and 35 g ai ha−1) was evaluated over two years (2010 and 2011). CSR 30 (superfine, scented) was more sensitive to higher rates (35 g ai ha−1) of azimsulfuron as compared to Pusa 1121 (fine, scented). Crop injuries were 8 and 28% in case of CSR 30; 5 and 15% in Pusa 1121 when applied with azimsulfuron 25 and 35 g ai ha−1, respectively. Azimsulfuron applied at 35 g ai ha−1 reduced yield in both cultivars but in CSR 30 yield reduction was twofold (11.5%) as that of Pusa 1121 (5.2%).

Physiological and biochemical indicators for assessing nitrogen-use efficiency in rice (Oryza sativa) genotypes under dry direct seeding

To achieve high productivity of labour and water in rice cropping, farmers in South Asia have recently shown more interest in dry direct-seeded rice (DSR). An understanding of physiological and biochemical traits associated with high grain yield and efficiency of nitrogen (N) use is important to the development of genotypes for DSR. We investigated this issue with rice genotypes adapted to DSR in response to N rates. A 2-year study was conducted in a factorial randomised complete block design with eight genotypes and two N rates (75 and 150 kg N ha–1). Almost all of the physiological and biochemical traits studied (e.g. plant height, chlorophyll content, panicle weight, soluble sugars, starch) in DSR improved with increasing N from 75 to 150 kg ha–1, resulting in a 6% increase in yield at 150 kg N ha–1 relative to 75 kg N ha–1. Partial factor productivity of N was highest for the genotype IET-23455 (72.4 kg kg–1) and lowest for the genotype AAUDR (37.4 kg kg–1). Our results suggest that genotypes such as IET-23455 can maintain grain yield at low N rates as N-efficient genotypes. The greater biochemical activity (nitrate reductase and glutamine synthetase, sugar, protein and proline) and higher photosynthetic N-use efficiency at low N rates could be used in selection for N-efficient rice genotypes for DSR.

Effect of phosphorus fertilization on its transformations in different soils under dry direct-Seeded rice

Effect of phosphorus fertilization on its transformations in different soils under dry direct-Seeded rice