Explore the vast range of titles available.

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.

Summary Rice is a staple food for half of the world's population. Changing climatic conditions, water and labour scarcity are the major challenges that shall limit future rice production. Dry direct‐seeded rice (DDSR) is emerging as an efficient, resources conserving, mechanized, climate smart and economically viable strategy to be adopted as an alternative to puddled transplanted rice (TPR) with the potential to address the problem of labour‐water shortages and ensure sustainable rice cultivation. Despite these benefits, several constraints obstruct the adoption of DDSR. In principle, the plant type for DDSR should be different from one for TPR, which could be achieved by developing rice varieties that combine the traits of upland and lowland varieties. In this context, recent advances in precise phenotyping and NGS‐based trait mapping led to identification of promising donors and QTLs/genes for DDSR favourable traits to be employed in genomic breeding. This review discusses the important traits influencing DDSR, research studies to clarify the need for breeding DDSR‐specific varieties to achieve enhanced grain yield, climate resilience and nutrition demand. We anticipate that in the coming years, genomic breeding for developing DDSR‐specific varieties would be a regular practice and might be further strengthened by combining superior haplotypes regulating important DDSR traits by haplotype‐based breeding.

Field experiments were performed in 2019 and 2020 to explore yield performance and biomass accumulation dynamics for different direct‐seeded rice methods after wheat straw return. The experimental treatments included two direct‐seeded rice methods (dry direct‐seeded rice and wet direct‐seeded rice) and two wheat straw return treatments (with and without wheat straw return). Wheat straw return had a negative impact on the yield and biomass of direct‐seeded rice. Compared with wet direct‐seeded rice, dry direct‐seeded rice was more negatively affected, with yield and biomass reduced by 6.7%–7.6% and 5.4%–6.5%, respectively. The yield loss was mainly associated with insufficient total spikelet numbers caused by reduced panicle numbers. A lower maximum tiller number caused by the restricted seedling tillering capacity was partly responsible for the inadequate panicle numbers in direct‐seeded rice after wheat straw return. Wheat straw return reduced the maximum and average rate of biomass accumulation, shortened the duration of effective biomass accumulation, and delayed the days to achieve the maximum rate of biomass accumulation for direct‐seeded rice. The negative effect of wheat straw return on direct‐seeded rice was concentrated mainly in the early stage; reduction in the average biomass accumulation rate in the early stage accounted for 61.1%–75.3% of the reduction in total average rate. Wet direct‐seeded rice had a higher average rate and amount of biomass accumulation at the early stage, a greater maximum tiller number, as well as a stronger photosynthetic ability and grain filling ability after heading, which contributed to improving panicle number and total spikelet number, ultimately increasing yield and biomass compared with dry direct‐seeded rice. These results demonstrate that wheat straw return reduced yield and biomass, mainly by inhibiting growth in the early stage of direct‐seeded rice. However, the wet direct‐seeding method decreased the losses in yield and biomass after wheat straw return. We performed a 2‐year field study to assess the effect of wheat straw return on dry and wet direct‐seeded rice, and we modeled biomass accumulation using the Richards equation. Wheat straw return reduced the yield and biomass of direct‐seeded rice, and this effect was greater for dry direct‐seeded rice. Wet direct‐seeded rice showed a higher rate and amount of biomass accumulation at the early growth stage, as well as higher tiller numbers, which improved panicle numbers and total spikelet numbers and thereby increased yield compared with dry direct‐seeded rice.

Transplanting rice appears to pose many problems, including depletion of freshwater reservoirs and competition for labor. Conversely, direct seeding allows us to overcome shortcomings associated with conventional transplanting. Nitrogen is a crucial nutrient needed for plant growth and yield. Therefore, this study was executed to analyze the influence of nitrogen on the performance of rice genotypes grown by direct seeding in wet soil. The experiment comprised various rice cultivars, i.e., Shalimar Rice-1, Shalimar Rice-3, Shalimar Rice-4, and Jhelum, and nitrogen (N) levels, i.e., 0, 90, 120, and 150 kg/ha. Shalimar Rice-4 produced a maximum grain yield (6.39 t/ha), followed by Shalimar Rice-3 and Jhelum). The application of 150 kg N/ha showed maximum values for growth parameters, yield attributing traits, and grain yield (6.68 t/ha); however, it remained at par with 120 kg N/ha. Crop water productivity was highest in Shalimar Rice-4 (0.49 kg/m3), and the same showed a consistent increase with increasing N levels from 0–150 kg/ha, with a comparable value of 0.49 to 0.51 recorded at 120 and 150 kg N/ha. Moreover, the Shalimar Rice-1 variety required the maximum in growing degree days (GDD) and helio-thermal units (HTU) to attain different phenological stages till physiological maturity (131 days). However, the cultivar Shalimar rice-4 (SR-4) performed better by registering significantly higher heat use efficiency (HUE) (4.44 kg/ha °C/day). Additionally, the highest net return and the benefit-cost ratio were registered by Shalimar Rice-4. B:C ratio of 1.75 was realized from application of 150 kg N/ha, which remained very close to that achieved with 120 kg N/ha. In conclusion, the rice cultivar Shalimar Rice-4 with the application of 120 kg N/ha could boost rice production under DSR in water-scarce regions of temperate northern India.

Small‐grain‐weight rice varieties are popular in South China. However, to maintain grain yields comparable to medium‐grain‐weight varieties, adjustments in nitrogen (N) and seeding rate management may be necessary. In this study, the small‐grain‐weight variety Mabayinzhan was direct‐seeded in a three‐season field experiment conducted from 2022 to 2023 in Qujiang County, Guangdong Province, South China, using four N rates and three seeding rates. The results showed that grain yield and grain weight ranged from 3.45 to 7.95 t ha−1 and from 11.4 to 14.1 mg, respectively, across all treatments with N application. The variation in grain yield was primarily attributed to differences in spikelets per m2, biomass production, and grain weight. Grain yield generally increased with higher N rates, but no significant difference was observed across the range of seeding rates. The grain yield responded more strongly to N rate than to seeding rate. The decrease in grain yield resulting from lower N rates could not be compensated by increasing seeding rate. While dense planting with reduced N application could improve N use efficiency (NUE), the increase in NUE was due to the reduced N rate rather than the seeding rate. Our findings indicate that high seeding rates are not essential for achieving high yields with a small‐grain‐weight rice variety. Moreover, increasing planting density while reducing N application may not be optimal for small‐grain‐weight inbred rice production under direct seeding conditions in South China.

Wet direct‐seeded rice (WDSR) is considered as a practicable substitute to transplanted‐flooded rice (TFR) because it copes with labor and water shortages, and reduces greenhouse gas emissions. However, the differences between WDSR and TFR in leaf senescence after flowering and the associated mechanisms have rarely been identified. In this study, the growth dynamics, SPAD value of flag leaf, dry matter accumulation and translocation, and the contents of plant hormones (ABA, CTKs, and GA3) in WDSR and TFR rice flag leaves after flowering were compared during the rice‐growing seasons of 2013, 2014, and 2018. The results showed that leaf senescence after flowering in WDSR was faster in comparison with TFR. The amount of dry matter acquired after flowering (ΔW) in WDSR was significantly lower and might be related to the faster leaf senescence after flowering in WDSR compared with TFR. The CTK content in flag leaves after flowering was lower in WDSR than in TFR, and CTK content declined earlier than SPAD value, which implied that decrease in CTK content could be a possible reason for the early leaf senescence in WDSR. In conclusion, faster leaf senescence after flowering in WDSR was mainly attributed to the decline in leaf CTK content. 1. Faster leaf senescence after flowering in WDSR as compared with TFR. 2. The differences in leaf senescence rates between WDSR and TFR might be attributed to the changes in contents of endogenous hormones, which then altered the accumulation and translocation of carbohydrates within the plants. 3. Techniques for delaying the rapid leaf senescence after flowering in WDSR should be developed in future.

Rice is one of the staple food crops of India, and Karnataka is one of the major rice-producing states. The primary method of rice establishment in Karnataka is transplanting, but farmers are opting to shift to direct-seeding of rice. Weed management is critical for realizing optimal yield of direct-seeded rice (DSR). The objective of this review was to synthesize the published literature on weeds and weed management in rice in Karnataka, identify improved weed-management technologies for delivery to farmers, and suggest research needs. Some 98 weed species are reported to be associated with rice in Karnataka. Weed control to date in Karnataka has mostly been based on herbicides. Hand-weeding was found to be effective in all methods of rice establishment. However, it is time-consuming, tedious, and costly because labor is becoming scarce and unavailable, and labor wages are higher. Several PRE and POST herbicides that were effective in other Asian countries were also found to be effective in managing weeds in rice established by different methods in Karnataka. Bensulfuron plus pretilachlor and pyrazosulfuron in aerobic rice and pendimethalin, thiobencarb, bispyribac-sodium, cyhalofop, fenoxaprop plus chlorimuron plus metsulfuron, and fenoxaprop plus ethoxysulfuron in dry-DSR were found effective in managing weeds. In wet-DSR, butachlor plus safener and pretilachlor plus safener were effective. Thiobencarb, pendimethalin, pretilachlor, azimsulfuron plus metsulfuron, bispyribac-sodium, butachlor, cinosulfuron, oxadiazon, and quinclorac were found promising for weed management in transplanted rice. Integration of herbicides with hand-weeding or intercultivation was found to be effective in rice established by different methods. Options that were found economical in managing weeds varied across the different rice-establishment methods. The need for developing location-specific, sustainable, integrated weed management and extension of available technologies for the farming community in Karnataka is emphasized. Nomenclature: Azimsulfuron; bensulfuron; bispyribac-sodium; butachlor; chlorimuron; cinosulfuron; cyhalofop; ethoxysulfuron; fenoxaprop; metsulfuron; oxadiazon; pendimethalin; pretilachlor; pyrazosulfuron; quinclorac; thiobencarb; rice, Oryza sativa L. El arroz es uno de los alimentos básicos de India, y Karnataka es uno de los estados con mayor producción de arroz. El método primario de establecimiento de arroz en Karnataka es el trasplante, pero los productores están optando por cambiar a la siembra directa del arroz. El manejo de malezas es crítico para alcanzar un rendimiento óptimo en arroz de siembra directa (DSR). El objetivo de esta revisión es sintetizar la literatura publicada acerca de las especies de malezas y el manejo de malezas en arroz en Karnataka, identificar tecnologías que mejoren el manejo de malezas, y sugerir cuáles son las necesidades de investigación. Noventa y ocho especies de malezas están reportadas como asociadas al arroz en Karnataka. Hasta la fecha, el control de malezas en Karnataka se ha basado mayoritariamente en el uso de herbicidas. Se encontró que la deshierba manual es efectiva en todos los métodos de establecimiento del arroz, sin embargo, toma mucho tiempo, es tediosa, y de alto costo porque la mano de obra es escaza o no está disponible del todo, y los salarios son cada vez más altos. También se encontró que varios herbicidas PRE y POST que son efectivos en otros países asiáticos son efectivos en el manejo de malezas en diferentes métodos de establecimiento de arroz en Karnataka. Se encontró que bensulfuron más pretilachlor y pyrazosulfuron en arroz aeróbico, y pendimethalin, thiobencarb, bispyribac-sodium, cyhalofop, fenoxaprop más chlorimuron más metsulfuron, y fenoxaprop más ethoxysulfuron en DSR-en seco fueron efectivos para el manejo de malezas. En DSR-en mojado, butolachlor más antídoto y pretilachlor más antídoto fueron efectivos. Thiobencarb, pendimethalin, pretilachlor, azimsulfuron más metsulfuron, bispyribac-sodium, butachlor, cinosulfuron, oxadiazon, y quinclorac fueron promisorios par el manejo de malezas en arroz trasplantado. La integración de herbicidas con la deshierba manual o el cultivo entre hileras fueron efectivos en arroz establecido con diferentes métodos. Las opciones que fueron económicas para manejar las malezas variaron según el método de establecimiento del arroz. Se hace énfasis en la necesidad de desarrollar y hacer disponibles a la comunidad agrícola en Karnataka, tecnologías para el manejo integrado de malezas que sean sostenibles y específicas para cada localidad.

Rice is a water-guzzling crop cultivated mostly through inefficient irrigation methods which leads to low water use efficiency and many environmental problems. Additionally, the export of virtual water through rice trading and the looming water crisis poses significant threats to the sustainability of rice production and food security. There are several alternative rice production methods to improve water use efficiency. These include aerobic rice, direct-seeded rice (DSR), alternate wetting and drying (AWD), saturated soil culture (SSC), drip-irrigated rice, a system of rice intensification (SRI), and smart irrigation with sensors and the Internet of Things (IoT). However, each method has its own advantages and disadvantages. For example, drip-irrigated rice and IoT-based automated irrigation are not feasible for poor farmers due to the high production costs associated with specialized machinery and tools. Similarly, aerobic rice, drip-irrigated rice, and the SRI are labor-intensive, making them unsuitable for areas with a shortage of labor. On the other hand, DSR is suitable for labor-scarce areas, provided herbicides are used to control weeds. In this article, the suitability of different water-saving rice production methods is reviewed based on factors such as climate, soil type, labor, energy, and greenhouse gas emissions, and their prospects and challenges are evaluated. Additionally, the article examines how cultural practices, such as seed treatment, weed control, and nutrition management, contribute to enhancing water use efficiency in rice production.

Dry direct-seeded rice is an alternative cropping technique that should require less water and labor than classical transplanted-flooded rice. Here, we studied growth, yield and resource use efficiency of rice cultivation in Central China, in 2012 and 2013. We compared dry direct-seeded rice and transplanted-flooded rice. For dry direct-seeded rice, we maintained aerobic conditions up to five-leaf stage followed by anaerobic conditions until maturity. We grew three rice cultivars: Lvhan1, Huanghuazhan, and Yangliangyou6. We measured grain yield, yield components, water consumed, water productivity and nitrogen use efficiency for grain production (NUEg). Our results show that grain yield of dry direct-seeded rice, of 9.01 Mg/ha, is identical to grain yield of transplanted-flooded rice, across cultivars and for both years. The grain yield of dry direct-seeded rice is mainly controlled by the panicle number. Moreover, dry direct-seeded rice uses 15.3 % less water than transplanted-flooded rice. Dry direct-seeded rice increased the grain nitrogen use efficiency by 20.3 % in 2012 and 11.2 % in 2013.

The aim of this study was to use small unmanned aerial vehicles (UAVs) for determining high-resolution normalized difference vegetation index (NDVI) values. Subsequently, these results were used to assess their correlations with fertilizer application levels and the yields of rice and wheat crops. For multispectral sensing, we flew two types of small UAVs (DJI Phantom 4 and DJI Phantom 4 Pro)—each equipped with a compact multispectral sensor (Parrot Sequoia). The information collected was composed of numerous RGB orthomosaic images as well as reflectance maps with spatial resolution greater than a ground sampling distance of 10.5 cm. From 223 UAV flight campaigns over 120 fields with a total area coverage of 77.48 ha, we determined that the highest efficiency for the UAV-based remote sensing measurement was approximately 19.8 ha per 10 min while flying 100 m above ground level. During image processing, we developed and used a batch image alignment algorithm—a program written in Python language–to calculate the NDVI values in experimental plots or fields in a batch of NDVI index maps. The color NDVI distribution maps of wide rice fields identified differences in stages of ripening and lodging-injury areas, which accorded with practical crop growth status from aboveground observation. For direct-seeded rice, variation in the grain yield was most closely related to that in the NDVI at the early reproductive and late ripening stages. For wheat, the NDVI values were highly correlated with the yield ( R 2 = 0.601–0.809) from the middle reproductive to the early ripening stages. Furthermore, using the NDVI values, it was possible to differentiate the levels of fertilizer application for both rice and wheat. These results indicate that the small UAV-derived NDVI values are effective for predicting yield and detecting fertilizer application levels during rice and wheat production.