Gulshan Mahajan

Productivity and Sustainability of the Rice–Wheat Cropping System in the Indo-Gangetic Plains of the Indian subcontinent: Problems, Opportunities, and Strategies

Abstract Rice and wheat are the staple foods for almost the entire Asian population and therefore they occupy a premium position among all food commodities. The era of the Green Revolution started during the early 1970s with wheat and rice and since then the rice–wheat cropping system of the Indo-Gangetic Plains has played a significant role in the food security of the region. However, recent years have witnessed a significant slowdown in the yield growth rate of this system and the sustainability of this important cropping system is at risk due to second-generation technology problems and mounting pressure on natural resources. Traditional cultivars and conventional agronomic practices are no longer able to even maintain the gains in productivity achieved during the past few decades. Demand for food is increasing with the increasing population and purchasing power of consumers. The rice–wheat cropping system is labor-, water-, and energy-intensive and it becomes less profitable as these resources become increasingly scarce and the problem is aggravated with deterioration of soil health, the emergence of new weeds, and emerging challenges of climate change. Therefore, a paradigm shift is required for enhancing the systems productivity and sustainability. Resource-conserving technologies involving zero- or minimum-tillage in wheat, dry direct seeding in rice, improved water- and nutrient-use efficiency, innovations in residue management to avoid straw burning, and crop diversification should assist in achieving sustainable productivity and allow farmers to reduce inputs, maximize yields, increase profitability, conserve the natural resource base, and reduce risk due to both environmental and economic factors. A number of technological innovation and diversification options have been suggested to overcome the systems sustainability problems but some of them have not been fully embraced by the farmers as these are expensive, knowledge-intensive, or do not fit into the system and have resulted in some other unforeseen problems. Different concerns and possible strategies needed to sustain the rice–wheat cropping system are discussed in this review on the basis of existing evidence and future challenges.

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.

Effect of nitrogen rates and weed control methods on weeds abundance and yield of direct-seeded rice

Field experiments were conducted at the Punjab Agricultural University, Ludhiana, India, during 2007–2008 to examine if nitrogen (N) rates and weed management practices using herbicides in combination with hand-weeding (HW) can improve crop competitiveness against weeds, and increase the yield, water productivity and profitability of direct-seeded rice (DSR). Increasing N application rate up to 150 kg ha−1 caused significant improvement in grain yield when the weeds were well controlled either by Pendimethalin + Bispyribac Na or by Pendimethalin + Bispyribac Na + 1 HW, respectively; however, under poor weed control condition (Pendimethalin + 1 HW), it resulted in a drastic reduction in yield. The highest net returns (

Effects of Planting Pattern and Cultivar on Weed and Crop Growth in Aerobic Rice System

1083) and water productivity (0.60 kg m−3) were observed for N application of 150 kg ha−1 and weeds were controlled with Pendimethain + Bispyribac Na + 1 HW. We suggest that Pendimethalin + Bispyribac Na + 1 HW is the best integrated weed management strategy to control weeds, and to increase yield, water productivity, and profitability. We propose that the simulation modelling tool be utilized in future for evaluating options for improving sustainable N and weed management policies especially when crop, weeds, soil, weather and management data are available for calibration and validation of appropriate and existing simulation model of rice.

Nonconventional Weed Management Strategies for Modern Agriculture

Abstract Weeds are a major biotic constraint to aerobic rice production in Asia. Research is needed on the effects of cultural practices on weed management in aerobic rice, including techniques such as planting pattern and competitive cultivars. Field experiments were conducted in Punjab, India, in the wet seasons of 2008 and 2009 to study the growth of weeds and two rice cultivars [PR 115 and Punjab (P.) Mehak 1] in relation to planting pattern (uniform rows [23-cm row spacing] and paired rows [15-, 30-, and 15-cm row spacings]) under aerobic conditions. Junglerice and rice flatsedge were the dominant weed species during the early stages of the crop, while Chinese sprangletop and large crabgrass were the predominant species during flowering stage of the crop. Weed dry matter was not affected by planting pattern of P. Mehak 1; however, for PR 115, weed dry matter was greater in rice grown in uniform rows (244 g m−2) than in paired rows (183 g m−2). Planting patterns did not affect weed-free crop growth and yield, but weeds tended to be more abundant in the uniform planting system, particularly under cultivar PR 115. Consequently, this cultivar grew and yielded better under the paired rows when weeds were present. The cultivar PR 115 had greater yield potential than P. Mehak 1, but growth and productivity of P. Mehak 1 were unaffected by the planting patterns, suggesting better competitive ability against weeds than PR 115. The results imply that yield of some aerobic rice cultivars may be improved by exploring competitiveness of rice cultivars through paired row planting patterns. There is a need to study plasticity changes for cultivars which respond with more competiveness in paired rows. The identified traits could be useful as selection criteria for screening weed-competitive cultivars in paired row pattern. Nomenclature: Junglerice, Echinochloa colona (L.) Link ECHCO; rice flatsedge, Cyperus iria L. CYPIR; Chinese sprangletop, Leptochloa chinensis (L.) Nees LEFCH; large crabgrass, Digitaria sanguinalis (L.) Scop. DIGSA; rice, Oryza sativa L.

Herbicide Options for Weed Control in Dry-Seeded Aromatic Rice in India

Abstract Weeds are a significant problem in crop production and their management in modern agriculture is crucial to avoid yield losses and ensure food security. Intensive agricultural practices, changing climate, and natural disasters affect weed dynamics and that requires a change in weed management protocols. The existing manual control options are no longer viable because of labor shortages; chemical control options are limited by ecodegradation, health hazards, and development of herbicide resistance in weeds. We are therefore reviewing some potential nonconventional weed management strategies for modern agriculture that are viable, feasible, and efficient. Improvement in tillage regimes has long been identified as an impressive weed-control measure. Harvest weed seed control and seed predation have been shown as potential tools for reducing weed emergence and seed bank reserves. Development in the field of allelopathy for weed management has led to new techniques for weed control. The remarkable role of biotechnological advancements in developing herbicide-resistant crops, bioherbicides, and harnessing the allelopathic potential of crops is also worth mentioning in a modern weed management program. Thermal weed management has also been observed as a useful technique, especially under conservation agriculture systems. Last, precision weed management has been elaborated with sufficient details. The role of remote sensing, modeling, and robotics as an integral part of precision weed management has been highlighted in a realistic manner. All these strategies are viable for today’s agriculture; however, site-specific selection and the use of right combinations will be the key to success. No single strategy is perfect, and therefore an integrated approach may provide better results. Future research is needed to explore the potential of these strategies and to optimize them on technological and cultural bases. The adoption of such methods may improve the efficiency of cropping systems under sustainable and conservation practices.

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

Abstract The looming water crisis and shortage of labor during rice transplanting in northwest India have led researchers to develop alternative methods to transition away from puddled transplanted rice. In this context, dry-seeded rice (DSR) is emerging as an efficient production technology to replace puddled transplanted rice. Weeds, however, are the main biological constraints to its success. A study comprising 12 treatments was conducted to evaluate the efficacy of PRE (pendimethalin and pyrazosulfuron) and POST herbicides (bispyribac, penoxsulam, and azimsulfuron) applied either alone or in a sequence for weed control in dry-seeded fine rice cv. ‘Punjab Mehak 1’. Results indicated that the single application of pendimethalin (750 g ai ha−1) PRE, pyrazosulfuron (15 g ai ha−1) PRE, bispyribac-sodium (25 g ai ha−1) POST, penoxsulam (25 g ai ha−1) POST, and azimsulfuron (20 g ai ha−1) POST reduced total weed biomass by 75, 68, 73, 70, and 72%, respectively, compared with the nontreated control at flowering stage of the crop. Azimsulfuron POST and pyrazosulfuron PRE proved effective against purple nutsedge and crowfootgrass, respectively. Chinese sprangletop, large crabgrass, and junglerice were effectively controlled with pendimethalin PRE. POST application of bispyribac-sodium and penoxsulam provided effective control of rice flatsedge. Compared to the nontreated control, grain yield following the single application of pendimethalin PRE, pyrazosulfuron PRE, bispyribac-sodium POST, penoxsulam POST, and azimsulfuron POST increased by 149, 119, 138, 124, and 144%, respectively. The sequential application of herbicides proved better than single applications. The lowest weed biomass was observed with the sequential application of pendimethalin PRE followed by azimsulfuron POST, and rice yielded 228% more than the nontreated control following this treatment. The results of this study are important for farmers growing DSR in making decisions regarding the application of POST herbicides, according to existing weed flora in the field. Nomenclature: Azimsulfuron; bispyribac-sodium; pendimethalin; penoxsulam; pyrazosulfuron; Chinese sprangletop; Leptochloa chinensis (L.) Nees LEFCH; crowfootgrass; Dactyloctenium aegyptium (L.) Willd. DTTAE; junglerice; Echinichloa colona (L.) Link ECHCO; large crabgrass; Digitaria sanguinalis (L.) Scop.; DIGSA; purple nutsedge; Cyperus rotundus L. CYPRO; rice flatsedge; Cyperus iria L. CYPIR; rice; Oryza sativa L. Resumen La creciente crisis por escasez de agua y de mano de obra durante el trasplante de arroz en el noroeste de India ha llevado a los investigadores a desarrollar métodos alternativos para cambiar las prácticas de trasplante en lodo. En este contexto, el uso de siembra de arroz en seco (DSR) está surgiendo como una tecnología de producción eficiente para remplazar el trasplante de arroz en lodo. Sin embargo, las malezas son uno de los impedimentos biológicos más importantes para el éxito de esta tecnología. Se realizó un estudio compuesto de 12 tratamientos para evaluar la eficacia de herbicidas PRE (pendimethalin y pyroxasulfuron) y POST (bispyribac, penoxsulam, y azimsulfuron) aplicados ya sea solos o en secuencia para el control de malezas en arroz fino cv. ‘Punjab Mehak 1′ sembrado en seco. Los resultados indicaron que una sola aplicación PRE de pendimethalin (750 g ai ha−1), PRE de pyrazosulfuron (15 g ai ha−1), POST de bispyribac-sodium (25 g ai ha−1), POST de penoxsulam (25 g ai ha−1), y POST de azimsulfuron (20 g ai ha−1), redujo la biomasa total de malezas en 75, 68, 73, 70, y 72%, respectivamente, al compararse con el testigo no-tratado en el estado de floración del cultivo. Azimsulfuron POST y pyrazosulfuron PRE probaron ser efectivos contra Cyperus rotundus y Dacyloctenium aegyptium, respectivamente. Leptochloa chinensis, Digitaria sanguinalis y Echinochloa colona fueron controlados efectivamente con pendimethalin PRE. La aplicación POST de bispyribac-sodium y penoxsulam brindó un control efectivo de Cyperus iria. Al compararse con el testigo no-tratado, el rendimiento en grano después de una sola aplicación de pendimenthalin PRE, pyrazosulfuron PRE, bispyribac-sodium POST, penoxsulam POST, y azimsulfuron POST aumentó en 149, 119, 138, 124, y 144%, respectivamente. La aplicación secuencial de herbicidas probó ser mejor que las aplicaciones solas. La menor biomasa de malezas se observó con la aplicación secuencial de pendimethalin PRE seguido por azimsulfuron POST, y el arroz rindió 228% más que el testigo no-tratado. Los resultados de este estudio son importantes para los productores usando DSR y que toman decisiones en relación a la aplicación POST de herbicidas, según la flora de malezas existente en el campo.

Performance and Water-use Efficiency of Rice Relative to Establishment Methods 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 rate was inversely correlated to weed interference. The results suggested that higher seed rates caused significant reductions in weed dry matter, whereas higher than optimum seed rate (15–30 kg/ha) caused reduction in yield. Of all the seeding rates used, 15–30 kg/ha had the lowest grain-yield losses caused by weeds. Therefore, it was concluded that optimum seed rate in direct-seeded rice would minimize the effect of weed competition on rice growth and grain yield and thus would reduce herbicide use, promoting integrated-weed management. Further, this proposition improves economy of the farmers who are thinking to shift to hybrid rice, whose seed is very costly. This investigation supports use of hybrid rice cultivars in DSR using a seed rate of 15–30 kg/ha.

Influence of Early and Delayed Transplantation of Paddy on Physicochemical, Pasting, Cooking, Textural, and Protein Characteristics of Milled Rice

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.

Yield and Nitrogen-Use Efficiency of Aromatic Rice Cultivars in Response to Nitrogen Fertilizer

ABSTRACT Milled rice of four indica cultivars (PR114, PR116, PR118, and PAU201) obtained from early (June 5 and 15) and delayed (June 25 and July 5) transplanted paddy was evaluated for physicochemical, pasting, cooking, and protein characteristics. During the grain-filling and development stage, early transplanted paddy experienced average maximum and minimum temperatures of 32.8 and 22.3°C, respectively, against 30.8 and 15°C, respectively, for delayed transplanted paddy. Lightness (L*) value, protein content, and lipid content of milled rice were lower, whereas apparent amylose content, cooked grain hardness, final viscosity, and setback viscosity were higher in the delayed transplanted paddy. Whiteness of milled rice of PR114, PR116, and PR118 from delayed transplanted paddy was lower than milled rice from early transplanted paddy. PAU201 did not show any change in whiteness with delayed transplantation. Cooked rice of PAU201 showed exceptionally higher adhesiveness and lower hardness compared with ot...