Rice Establishment Methods Research Articles

Effect of silicon fertilization and crop establishment methods on yield, soil quality and silicon uptake of rice (Oryza sativa)

A field experiment was carried out at ICAR-Indian Agricultural Research Institute, New Delhi during kharif 2015 and 2016 to determine the effects of rice establishment method, silicon application levels and silicon solubilizing bacteria on silicon concentrations and uptake by rice (Oryza sativa) and soil microbial parameters in rice-wheat cropping system. The experiment was laid out in split-split plot design and replicated thrice. The experiment was conducted with 24 treatment combinations including rice establishment methods in main plot, silicon level in sub plot and silicon solubilizing microbes in sub-sub plot. Silicon concentration in grain and straw was highest in crop establishment of aerobic rice and lowest in TPR methods during both the years. Tested aerobic rice establishment methods significantly influenced the microbial biomass carbon (278.2 and 289.3 μg/g soil), soil dehydrogenase activity (202.3 and 198.3 μg TPF/g soil/day) and total count of silicon solubilizing bacteria (222.5 and 255.9 × 102 cfu/g soil) compared to SRI and TPR and the highest silicon concentration and uptake, microbial biomass carbon (285.9 μg/g soil), dehydrogenase activity (189.7 μg TPF/g soil/day) and total count of silicon solubilizing bacteria (239.6 102 cfu/g soil) was recorded with silicon application 120 kg/ha which at par with 80 kg/ha but statistically superior over to control and 40 kg/ha in terms of nutrient uptake in grain and straw and soil quality parameters during both years of study.

Rice (Oryza sativa L.) Establishment Techniques and Their Implications for Soil Properties, Global Warming Potential Mitigation and Crop Yields

Rice-based intensive cropping systems require high input levels making them less profitable and vulnerable to the reduced availability of labor and water in Asia. With continuous conventional puddled rice transplanting, the situation is exacerbated by damaged soil structure, declining underground water and decreasing land and water productivity. To minimize these negative effects a range of new crop establishment practices have been developed (zero tillage, dry direct seeding, wet direct seeding, water seeding, strip planting, bed planting, non-puddled transplanting of rice, mechanical transplanting of rice crop and combinations thereof) with varying effects on soil health, crop productivity, resource saving and global warming mitigation potential. Some of these allow Conservation Agriculture (CA) to be practiced in the rice-based mono-, double- and triple cropping systems. Innovations in machinery especially for smallholder farms have supported the adoption of the new establishment techniques. Non-puddling establishment of rice together with increased crop residue retention increased soil organic carbon by 79% and total N (TN) in soil by 62% relative to conventional puddling practice. Rice establishment methods (direct seeding of rice, system of rice intensification and non-puddled transplanting of rice) improve soil health by improving the physical (reduced bulk density, increased porosity, available water content), chemical (increased phosphorus, potassium and sulphur in their available forms) and biological properties (microbiome structure, microbial biomass C and N) of the soil. Even in the first year of its practice, the non-puddled transplanting method of rice establishment and CA practices for other crops increase the productivity of the rice-based cropping systems. Estimates suggest global warming potential (GWP) (the overall net effect) can be reduced by a quarter by replacing conventional puddling of rice by direct-seeded rice in the Indo-Gangetic Plains for the rice-based cropping system. Moreover, non-puddled transplanting of rice saves 35% of the net life cycle greenhouse gases (GHGs) compared with the conventional practice by a combination of decreasing greenhouse gases emissions from soil and increasing soil organic carbon (SOC). Though the system of rice intensification decreases net GHG emission, the practice releases 1.5 times greater N2O due to the increased soil aeration. There is no single rice establishment technology that is superior to others in all circumstances, rather a range of effective technologies that can be applied to different agro-climates, demography and farm typologies.

Long term effects of rice establishment methods on physical properties and rice productivity in vertisols of Chhattisgarh plain

The farmer field study was carried out during 2016 at village Saida, Takhatpur Tehsil in Bilaspur district of Chhattisgarh to evaluate the “Long term effects of rice establishment methods on physical properties and rice productivity in Vertisols of Chhattisgarh plain”. The trial was laid out in Randomized block design with twelve replications and three treatments in rice based cropping system in Vertisols. The study on the long-term effect of rice establishment methods on soil physical, chemical, biological properties and crop productivity were evaluated after harvest of rice crop. In this study, three rice establishment methods i.e. transplanting, broadcast-biasi and direct seeded line sowing were laid in main treatment. A study was undertaken to characterize the soil resources of the investigation field. The residual effect of rice establishment methods on soil physical properties like bulk density, hydraulic conductivity, penetration resistance, water holding capacity and crack volume were significantly affected by the treatments. Transplanting method significantly increased the bulk density of surface soil (0-15 cm) and sub-surface layer i.e. (15-30 and 30-45 cm) but non-significant affect was obtained at lower (45-60 cm) depth. The hydraulic conductivity was found maximum in surface layer under direct seeded method and increases as per depth was decreased. Penetration resistance was recorded significantly increase with increase in depth. Water holding capacity was significantly increased with direct seeded (LS) method and minimum was recorded in transplanting method. Crack volume was significantly higher in transplanting method over other methods of rice cultivation.

Nutrient management for higher rice productivity under different establishment methods

A field experiment was conducted during Kharif, 2017 and 2018 at Department of Rice, Tamil Nadu Agricultural University, Coimbatore, to study the nutrient management for higher productivity in different rice establishment methods. Experimental trial was conducted in split plot design with three replications. In main plot, different rice establishment methods viz., M1: Machine transplanting method, M2: Conventional method, M3: System of Rice Intensification (SRI) method; where as in sub-plot, the nutrient management viz., S1: 100 % of recommended inorganic fertilizer (120:60:40 kg NPK/ha), S2: 75 % inorganic + 25 % organic (equivalent of N dose), S3: 150 % RDF (180:90:60 kg NPK/ha), S4: LCC based N application, S5: Location specific fertilizer management (150:50:50 kg NPK/ha). Based on the two years of study, the results revealed that among the different methods of planting and nutrient sources, SRI method of planting with LCC based N application recorded higher grain yield (6114 kg/ha) which was followed by machine transplanting method. The net return (Rs.55,882/-) and BCR (2.54) was higher under SRI method with LCC based N application when compared to other methods.

Nutrient management in different rice (Oryza sativa L.) Establishment methods under black clay soils of Tungabadra command

Nutrient management in different rice (Oryza sativa L.) Establishment methods under black clay soils of Tungabadra command

Evaluation of water saving rice production systems

An experiment was conducted during kharif, 2010 at the College Farm, Prof.jayashanakar Telangana State Agril.University (Formerly Acharya N.G.Ranga Agril.University), Rajendranagar, Hyderabad to evaluate different rice production technologies in order to assess the rice water productivity and water input under different methods of establishment. The treatments consisted of four methods of rice establishment -aerobic rice on raised beds with drip fertigation, aerobic rice on flat beds with surface irrigation, System of Rice Intensification (SRI) and transplanted low land rice (conventional method) as main plots and three levels of Nitrogen (100, 150 and 200 kg N ha-1) in subplots. The grain yield obtained with transplanted low land and SRI methods of rice cultivation was comparable (non-significant) and significantly higher than that of aerobic rice grown either on raised beds with drip fertigation or on flat beds with surface irrigation. Among N levels - the grain yield obtained with 100 kg N ha-1 was comparable with that of 150 kg N ha-1 and significantly lower than that of 200 kg N ha-1. The results indicated that the aerobic rice grown either on raised beds or on flat beds has consumed less quantity of irrigation water as compared to SRI and conventional transplanted low land rice. The water productivity was higher in SRI followed by aerobic rice sown on raised beds. The lowest water productivity was observed in conventional transplanted low land rice.

Influence of different rice establishment methods and nutrient levels on soil enzyme activity, nutrient status and grain yield of rice in North Coastal Zone of Andhra Pradesh

To enhance productivity, alleviate environmental and management constraints and enhance farmers' income in the rice, new approaches that are labour-saving, more productive and sustainable need to be developed. Experiment was formulated to know the impact/influence of different rice establishment methods and different levels of nitrogen application on soil and crop productivity of rice. Results revealed that, among different rice establishment systems, machine transplanting recorded significantly higher yields followed by SRI method. Lowest yields were recorded in dry seed broadcasting method. With increasing nitrogen levels, yields were increased in all the systems and further enhancement of rice yields were observed with potassium nitrate foliar spray along with chemical fertilizers. Soil enzyme activity particularly urease and dehydrogenase was significantly high under normal planting and SRI method of planting, respectively and lowest enzyme activities were recorded in broadcasting of dry seed. Soil organic carbon content also followed the same trend as like enzyme activity. With regard to soil nutrient status, significant differences were not observed in phosphorus and potassium, however available nitrogen status was increased with increasing fertilizer levels and among different methods, drum seeding recorded highest status (286 kg ha-1).

QTL mapping and effect confirmation for anaerobic germination tolerance derived from the japonica weedy rice landrace PBR

AbstractAs one of the main rice establishment methods, direct seeding has the advantages of saving labour and reducing costs for farmers. However, the expansion of direct seeding has been constrained by poorly levelled fields, heavy rainfall and poor drainage after sowing. The development of cultivars with anaerobic germination tolerance could improve or overcome these shortcomings of most rice under flooding conditions. In this study, a japonica‐type rice with anaerobic germination tolerance was suggested as a new genetic source and QTL analysis was carried out to improve adaptation to direct seeding. Three QTLs, qAG1, qAG3 and qAG11, were identified, explaining 13.44%, 6.71% and 14.52% of the phenotypic variance, respectively. In an evaluation of the most effective QTL combination, two QTL combinations (qAG1NP + qAG3PBR + qAG11PBR and qAG1NP + qAG11PBR) showed stable survival rates under submergence of filed condition. Based on the results, we will characterize the candidate genes within the detected target regions in further research, and the lines with advantageous alleles will be used to develop reliable cultivars to support the wide adoption of direct‐seeding practices in japonica rice.

Effect of natural safe rock minerals on growth, yield and quality of rice (Oryza sativa) in rice-wheat cropping system

A field experiment was conducted during two Kharif seasons of 2016 and 2017 at the research farm of ICARIndian Agricultural Research Institute, New Delhi to study the effect of Safe Rock Mineral (SRM) on productivity and quality of rice in rice-wheat cropping system. The experiment was carried out in randomized block design with three replications involving two rice (Oryza sativa) establishment methods (aerobic rice and transplanted rice) and six crop nutrition levels on rice-wheat sequence. The results indicate that, in general transplanted rice performed comparatively better in terms of growth, yield and quality parameters compared to aerobic rice. Different nutritional level improved the productivity of rice and succeeding wheat crop in both the years significantly. Among nutrient management practices, highest plant growth, yield attributes and yield of rice were obtained with the application of SRM application @ 250 kg/ha + 100% RDF and it was followed by No SRM application + 100% RDF, SRM application @ 250 kg/ha + 50% RDF (Chemical) + 25% RDF (Organic-FYM) and SRM application @ 250 kg/ha + 50% RDF (Organic-FYM). Integrated nutrient management with SRM application @ 250 kg/ha + 100% RDF increased grain protein content significantly over only SRM application @ 250 kg/ha. An increase of 16.42% and 18.07% in grain protein was recorded under aerobic and transplanted method of rice, respectively. It was concluded that integrated application of SRM @ 250 kg/ha + 100% RDF gave the highest growth and productivity of rice and with this treatment grain yield was 32.2% and 32.9% higher than only SRM application at @ 250 kg/ha under aerobic and transplanted conditions respectively.

Agroecological and Socioeconomic Significance of Different Rice Establishment Methods

Agroecological and Socioeconomic Significance of Different Rice Establishment Methods

Direct seeding for rice production increased soil erosion and phosphorus runoff losses in subtropical China

Estimating soil erosion and nutrient losses from surface runoff in paddy fields is essential for the assessment of sustainable rice (Oryza sativa L.) production and water quality protection. Different rice establishment methods have been used in the last three decades in Asia; however, it is still unclear how these methods influence sustainable agriculture and environmental protection in humid areas. The aim of this study was to evaluate the impacts of rice establishment method on soil erosion and phosphorus (P) losses from surface runoff in Hydragric Anthrosols under a subtropical monsoon climate. Total suspended solids (TSS), total P (TP), dissolved P (DP), and particulate P (PP) runoff losses were measured under four rice establishment treatments in 2013 and 2014, including traditional manual transplanting (TT), mechanical transplanting (MT), dry direct seeding (DD), and wet direct seeding (WD). The results showed that the seasonal TSS in the runoff varied from 59.9 to 829.8 kg ha−1 in the two years. Compared with TT, the DD significantly increased the TSS by 481% in 2013 and by 349% in 2014, while the WD significantly increased TSS by 783% in 2013 and by 571% in 2014. In the 2013 and 2014 rice seasons, the field-observed TP runoff losses were from 0.18 to 1.51 kg ha−1. Compared with TT, the DD significantly increased the TP lost by 222% in 2013 and by 197% in 2014, whereas the WD significantly increased the TP lost by 483% in 2013 and by 387% in 2014. However, the TSS and P losses from the MT and TT were similar in both years. The PP runoff losses accounted for 58–77% of the seasonal TP lost. These findings demonstrate that the conversion of traditional manual transplanting to direct seeding increased soil erosion and P runoff losses in subtropical China.

Tillage and crop establishment options for enhancing the productivity, profitability, and resource use efficiency of rice-rabi systems of the salt-affected coastal lowlands of eastern India

Farmers in the rainfed salt-affected coastal areas of eastern India face challenges of flooding, salinity, scarcity of irrigation water, and insufficient rainfall that affect crop production and environmental sustainability. This study evaluated three rice establishment methods [dry-seeded rice (DSR), non-puddled transplanted rice (Non-PTR), and puddled transplanted rice (PTR)] during the wet season/kharif and three tillage practices [zero-tillage (ZT), conventional tillage (CT), and raised-bed sowing (RBS)] for dry-season/rabi crops (maize and rapeseed) in a replicated experiment. The experimental site was in the rainfed and salt-affected coastal lowland area of West Bengal, India, and rice was grown in three successive wet seasons (2013–16), with each rice crop followed by maize or rapeseed in the dry season. Transplanted rice was adversely affected by submergence each year due to heavy rain after transplanting, whereas DSR was less affected as the plants were taller at the time the heavy rains began. Rice grain yields were similar (4.5–5.1 t ha−1), however, among the three rice establishment methods, and, further, rice yields were not affected by rabi-season tillage practices. The net returns and the benefit-cost ratio (BCR) were greater in DSR because of the reduced costs of land preparation. Rapeseed grown after non-puddled rice (DSR and Non-PTR) gave 25–44% higher yield than rapeseed grown after PTR, and the yields of maize were 8–13% higher when grown after either DSR or Non-PTR than after PTR. DSR and Non-PTR also had positive effects on soil quality: bulk density was lower after the third-year rice crop and soil salinity decreased during each dry season (Dec-April) just after the rice crop compared with PTR. Maize yield was highest in RBS (5.8 t ha−1), followed by CT (4.1 t ha−1) and ZT (3.6 t ha−1), whereas rapeseed produced the highest yield under ZT (0.86 t ha−1) vis-à-vis RBS and CT (0.6 t ha−1). Net returns for maize were highest with crops on RBS and in rapeseed with ZT. Maize provided a higher economic return than rapeseed (USD 301-405 ha−1 in maize; USD 5–113 ha−1 in rapeseed) but it (maize) required 25 cm more irrigation water and 3 GJ ha−1 more energy input for cultivation. This study indicates that rice-maize could be more profitable than rice-rapeseed for the salt-affected coastal areas in India, and that, to improve productivity and profitability in this rotation, rice should be established as DSR or Non-PTR followed by maize on RBS in the coastal regions.

Improving Water and Nutrient Use Efficiency in Rice by Changing Crop Establishment Methods, Application of Microbial Inoculations, and Zn Fertilization.

A field experiment was conducted during the wet seasons of 2013 and 2014 to evaluate the effect of three rice establishment methods: viz. puddled transplanted rice (PTR), system of rice intensification (SRI) and aerobic rice system (ARS), two cyanobacteria based inoculants, viz. Anabaena sp (CR1) + Providencia sp (PR3) consortium and Anabaena–Pseudomonas (An‐Ps) biofilm formulation, and zinc (Zn) fertilization on the rice yield, water productivity, and nutrient use efficiency. The yields of rough, brown and milled rice were highest in SRI, which was on par with PTR and both methods proved significantly superior to ARS in both years. The total water productivity of rough and brown rice in the first year was significantly higher in SRI. The SRI method saved 21.9% and 27.4% irrigation water over PTR, and savings in ARS were 37.4% and 50.8% in first and second year respectively, over PTR. The use of An‐Ps biofilm formulation along with 75% RDN improved the agronomic use efficiency of both nitrogenous and phosphatic fertilizers applied. On the basis of the present study, it can be concluded that SRI improved rice yields and water productivity; while involvement of An‐Ps biofilm formulation can be recommended for improved nutrient use efficiency.

Weed management in rice established by different methods

The field experiment was conducted at Agronomy Department Farm, College of Agriculture, Dapoli, during Kharif (rainy) seasons 2016 and 2017 to study the effect of established by different methods of rice establishment on weeds. The field experiment was laid out in a strip plot design comprising of twenty five treatment combinations replicated thrice. The horizontal strips comprised five rice establishment methods, viz. sowing of dry seeds by drum seeder at onset of monsoon, sowing of sprouted seeds (Rahu) by drum seeder in puddled field, broadcasting of sprouted seeds (Rahu) in puddled field, system of rice intensification (SRI) method and conventional transplanting. The vertical strips consisted five weed management practices, viz. need based two hand weedings at 20/30 and 40/60 DAS/DAT, pre-emergence application of oxadiargyl 80 WP 100 g/ha + 1 hand weeding at 20/30 DAS/DAT, pre-emergence application of oxadiargyl 80 WP 100 g/ha + 1 hand weeding at 40/60 DAS/DAT, pre-emergence application of oxadiargyl 80 WP 100 g/ha + post-emergence application of Almix 20 WP 4 g/ha and unweeded control. SRI method with two hand weedings carried out at 20 and 40 DAT recorded highest grain and straw yield of rice and lowest weed density and dry weight of weeds as compared to remaining treatment combinations during both the seasons.

Soil carbon pools and enzyme activities in aggregate size fractions after seven years of conservation agriculture in a rice–wheat system

Decline in soil organic carbon (SOC) due to intensive tillage and removal or burning of crop residues is considered a major threat to maintaining soil quality and meeting future challenges of food production at national and global scales. Adoption of conservation-agriculture practices (no till and residue retention) is necessary to promote soil structural stability and increases in SOC content and enzyme activities. We evaluated the impact of tillage and residue-management practices on yield, soil labile-C pools, aggregate stability and soil enzyme activities after seven cycles of a rice (Oryza sativa L.)–wheat (Triticum aestivum L.) system on the Indo-Gangetic Plain of India. Treatments included four combinations of tillage and crop establishment in rice (main plots), and three combinations of tillage and residue management in wheat (subplots). Irrespective of rice-establishment method, mean grain yield of no-till wheat with rice-residue mulch (NTW+RR) was 9% and 22% higher, respectively, than of conventional-till (CTW) or no-till wheat with no rice-residue mulch. Soil C pools (very labile, labile, less-labile and non-labile) were significantly higher under a no-till dry-seeded rice (NTDSR)–NTW+RR cycle than conventional-till puddled transplanted rice–CTW. Macro-aggregates (>0.25 mm) had higher labile C pools, glomalin content and enzyme activities than micro-aggregates. NTW+RR significantly increased soil C pools within both macro- and micro-aggregates. Compared with CTW, NTW+RR increased soil dehydrogenase, cellulase and alkaline phosphatase activities by 23%, 34% and 14%, and water-soluble organic C by 31%, and increased water-stable aggregates and mean-weight-diameter. NTDSR–NTW+RR increased SOC, enzyme activity, aggregate stability and wheat grain yield. Results indicated that soil labile-C pools across aggregate fractions were the most sensitive indicators of soil quality when determining the effects of changes in management practices. Furthermore, adoption of no till and residue retention may improve sustainability in rice–wheat systems of the Indo-Gangetic Plain.

Study of different rice establishment methods on growth and yield of different varieties

A field experiment was conducted in spit plot design with three replication to “to study different rice establishment methods on growth, yield and different varieties” was conducted at Agronomy farm, College of Agriculture, Dapoli, Distt. Ratnagiri (M.S.) during kharif season of 2014 on was sandy clay loam in texture, moderately acidic in pH (5.63), medium in organic carbon content (0.82 %), electrical conductivity (Ec) 0.035 dSm-1 , medium in available nitrogen (284.82 kg/ha), low in available phosphorus (14.63 kg/ha) and high in available potassium (248.45 kg/ha). The highest plant height (71.09 cm), effective tillers (360.58 m2), length of panicle (21.07 cm), test weight (22.24 g), straw yield (47.42 q ha-1), weight of per panicle (2.15 g), number of filled grains per panicle (97.08) and B:C ratio (1:2.23) were recorded in line transplanting technique. Based on the results obtained, it can be concluded that in areas where labour is available and cheap, transplanting as per as recommended (21 days old age seedling) is a better establishment methods of rice because it produces more yield and gross monetary economic return than other methods.

Discriminating transplanted and direct seeded rice using Sentinel-1 intensity data

Improved rice crop and water management practices that make the sustainable use of resources more efficient are important interventions towards a more food secure future. A remote sensing-based detection of different rice crop management practices, such as crop establishment method (transplanting or direct seeding), can provide timely and cost-effective information on which practices are used as well as their spread and change over time as different management practices are adopted. Establishment method cannot be easily observed since it is a rapid event, but it can be inferred from resulting observable differences in land surface characteristics (i.e. field condition) and crop development (i.e. delayed or prolonged stages) that take place over a longer time. To examine this, we used temporal information from Synthetic Aperture Radar (SAR) backscatter to detect differences in field condition and rice growth, then related those to crop establishment practices in Nueva Ecija (Philippines). Specifically, multi-temporal, dual-polarised, C-band backscatter data at 20m spatial resolution was acquired from Sentinel-1A every 12 days over the study area during the dry season, from November 2016 to May 2017. Farmer surveys and field observations were conducted in four selected municipalities across the study area in 2017, providing information on field boundaries and crop management practices for 61 fields. Mean backscatter values were generated per rice field per SAR acquisition date. We matched the SAR acquisition dates with the reported dates for land management activities and with the estimated dates for when the crop growth stages occurred. The Mann-Whitney U test was used to identify significant differences in backscatter between the two practices during the land management activities and crop growth stages. Significant differences in cross-polarised, co-polarised and band ratio backscatter values were observed in the early growing season, specifically during land preparation, crop establishment, rice tillering and stem elongation. These findings indicate the possibility to discriminate crop establishment methods by SAR at those stages, suggesting that there is more opportunity for discrimination than has been presented in previous studies. Further testing in a wider range of environments, seasons, and management practices should be done to determine how reliably rice establishment methods can be detected. The increased use of dry and wet direct seeding has implications for many remote sensing-based rice detection methods that rely on a strong water signal (typical of transplanting) during the early season.

A diagnostic on-farm survey of the potential of seed drill and transplanter for mechanised rice establishment in Central Laos and Southern Cambodia

ABSTRACTDue to labour shortages in rural areas, traditional manual transplanting is often no longer feasible and alternative rice establishment methods are required in Central Laos and Southern Cambodia. The work reported here evaluated the potential of a seed drill and transplanter by comparing yield of over 200 crops established by different methods including broadcasting in farmer’s fields under their management in 3 seasons in Laos. In Cambodia, yield of rice established by drill planting was compared with farmers’ practice by broadcasting in two early wet seasons. When mechanised and manual establishment methods were compared in each of 10 farms in the same season in Laos, drilled crops produced slightly higher yield compared with manual planting. Similarly in Cambodia, the technology package including drill produced slightly higher yield and higher gross margin despite lower plant density than that of the farmer practice based on broadcasting. On the other hand, mean yield established using drill was 26% lower than manually transplanted crops across all seasons and villages in Laos, indicating that possibly drills were used in fields unsuitable to them. Mean yield established using transplanter across all fields was 16% lower than manually transplanted crops. Hill density of crops established from transplanter was lower than that from manual transplanting, and yield increased with increased hill density. The labour requirement and hence establishment cost were greatly reduced compared to manual transplanting. The results show the economic advantage of mechanised rice establishment particularly of seed drills.Abbreviations: WS: wet season; DS: dry season.

Correlation of Leaf and Root Senescence During Ripening in Dry Seeded and Transplanted Rice

Dry seeding is a resource-saving rice establishment method. With an equivalent yield, dry seeded flooded rice (DSR) has been considered as a replacement for traditional transplanted flooded rice (TFR). However, the differences in leaf and root senescence during grain filling between DSR and TFR were seldom identified. In this study, the root length, root tip number and leaf senescence of rice varieties Huanghuazhan and Yangliangyou 6 during ripening were compared between DSR and TFR. Results showed that top three leaves in DSR had the characteristics of relatively lower SPAD value, lower N content and premature leaf senescence. In addition, both the total root length and total root tip number of DSR were significantly lower than those of TFR. In conclusion, premature and quick leaf senescence was related with inadequate root length and root tip number during ripening, which might result from the deficiency of nitrogen supply in DSR. Techniques on improving leaf nitrogen status and delaying the leaf senescence during grain-filling in DSR should be developed in future researches.

Integrating mechanization with agronomy and breeding to ensure food security in China

Productivity of intensive rice cropping systems plays a pivotal role in national food security in China. By 2030, a 20% increase in rice yield will be required to meet the growing demand for food that will result from population growth. The success of China’s super hybrid rice was expected to provide an opportunity to cope with the increased demand for rice. However, in China the planting area of super hybrid rice is less than 8% of the national total rice planting area and the planting area of hybrid rice has continued to decline since 1996. The decreased planting area of hybrid rice is related to the shift in rice establishment methods from manual transplanting to direct seeding and mechanical transplanting. These shifts can result in increased seeding rates and reduced morphological advantages of heterosis (e.g. reduced panicle size), both of which can influence cultivar choice by rice farmers, who will tend to favor cheaper inbred cultivars. The shifts in rice establishment methods can also eliminate or reduce the seedling nursey period and subsequently shorten the growth duration and negatively affect the yield. We anticipate that the above problems will be resolved by integrating mechanization (e.g. designing high-precision seed sowing machines) with agronomy (e.g. improving management practices for increasing seed vigor) and breeding (e.g. developing high-yielding cultivars with short growth durations). This strategy also has implications for production of other crops in intensive farming systems in China and for other developing countries with rice-based intensive cropping systems.