Changes and determining factors of crop evapotranspiration derived from satellite-based dual crop coefficients in North China Plain

Evaluating actual crop evapotranspiration(ET_c) variations and their determining factors under changing climates is crucial for agricultural irrigation management and crop productivity improvement in nonhumid regions.This study analyzed the spatiotemporal characteristics and detected the determining factors of ET_c for winter wheat and summer maize rotation system from 2000 to 2017 in the North China Plain(NCP),by combining the FAO-56 dual crop coefficient approach with remot...     

Deficit irrigation management for rice using crop growth simulation model in an optimization framework

Optimization of irrigation water is an important issue in agricultural production for maximizing the return from the limited water availability. The current study proposes a simulation–optimization framework for developing optimal irrigation schedules for rice crop (Oryza sativa) under water deficit conditions. The framework utilizes a rice crop growth simulation model to identify the critical periods of growth that are highly sensitive to the reduction in final crop yield, and a genetic algorithm based optimizer develops the optimal water allocations during the crop growing period. The model ORYZA2000, which is employed as the crop growth simulation model, is calibrated and validated using field experimental data prior to incorporating in the proposed framework. The proposed framework was applied to a real world case study of a command area in southern India, and it was found that significant improvement in total yield can be achieved by the model compared to other water saving irrigation methods. The results of the study were highly encouraging and suggest that by employing a calibrated crop growth model combined with an optimization algorithm can lead to achieve maximum water use efficiency.     

Relations of rice seeding rates to crop and weed growth in aerobic rice

Aerobic rice describes a management adaptation to reduced irrigation water supplies but, due to reduced intervals of flooding in this system, this requires revised weed management approaches to reduce costs and provide effective weed control. One approach is to make the crop more competitive and reduce the effects of weeds on the crop by using higher rice seeding rates. A study was conducted in the Philippines and India in 2008 and 2009 to assess the relations of seeding rates (15-125 kg ha⁻¹) of hybrid and inbred varieties to crop and weed growth in aerobic rice. Plant densities, tillers, and biomass of rice increased linearly with increased in seeding rates under both weedy and weed free environments. Weed biomass decreased linearly with increasing seeding rates from 15 to 125 kg ha⁻¹. Panicles and grain yields of rice in competition with weeds increased in a quadratic relation with increased seeding rates at both locations; however, the response was flat in the weed free plots. A quadratic model predicted that seeding rates of 48-80 kg ha⁻¹ for the inbred varieties and 47-67 kg ha⁻¹ for the hybrid varieties were needed to achieve maximum grain yield when grown in the absence of weeds, while rates of 95-125 kg seed ha⁻¹ for the inbred varieties and 83-92 kg seed ha⁻¹ for the hybrid varieties were needed to achieve maximum yields in competition with weeds. On the basis of these results, seeding rates greater than 80 kg ha⁻¹ are advisable where there are risks of severe weed competition. Such high seeding rates may be prohibitive when using expensive seed, and maximum yields are not the only consideration for developing recommendations for optimizing economic returns for farmers. Results of the present study do suggest however that increasing seeding rates of aerobic rice does suppress weed growth and reduce grain yield losses from weed competition. This information could be incorporated in integrated crop management packages to manage weeds more effectively.     

Effects of crop establishment techniques on weeds and rice yield

Field and pot studies were conducted to evaluate the effects of seven rice establishment techniques {puddling transplanting (PT), no tillage transplanting (NTT), puddling drum wet seeding (PDWS), no tillage drum wet seeding (NTDWS), conventional tillage dry drilling (CTDD), furrow irrigated raised beds system dry drilling (FIRBSDD), and no-tillage dry-drilling (NTDD)} and water submergence stress on weeds and rice yield. The highest yield and least weed abundance were in the PT treatment. The direct seeded rice (DSR), both dry and wet exhibited severe weed infestation, and compared to transplanting showed reduced yield both in the presence and absence of weeds. The yield losses due to weeds in the DSR treatments ranged from 91.4 to 99.0%, compared to 16.0 and 42.0% in the transplanting treatments (PT and NTT). Weeds, including Cyperus rotundus L., Dactyloctenium aegyptium (L.) Willd., Digera arvensis Forsk., Phyllanthus niruri L., and Trianthema portulacastrum L. which were found in the un-puddled DSR treatments were absent in the puddled plots, particularly the PT treatments. In pot studies, continuous water-submergence (2.5 cm) for 20 days reduced the emergence of C. rotundus, D. aegyptium, T. portulacastrum, and Echinochloa crus-galli (L.) Beauv. by 99.4, 100, 100, and 24.4%, respectively, compared to alternate wetting–drying. In farmer's field studies, when compared to the PT treatments, the DSR treatments exhibited lower yields (15.8%) with coarse varieties (HKR-47 & IR-64), but fine cultivars (Sharbati & PB-1) exhibited similar yields under both systems. In view of the shortage of labour for manual transplanting, there is a need to develop suitable cultivars for aerobic system conditions (unpuddled DSR and NT machine-transplanting).     

浅谈水稻冷害指标的调整

针对吉林省辽河农垦管理区水稻田与旱田小气候不同特点,以观测的事实为依据,提出水稻田冷害指标的调整建议:水稻移栽始期日均气温稳定通过11.2℃;6月10日以前,水稻秧苗受冷害温度下调为<15℃;而7月份冷害温度应上调为<17.7℃;8月份上调为<18.4℃;9月份为<19.0℃。并指明,夜间是水田预防低温冷害的重点时间。     

Estimated evapotranspiration of rice based on pan evaporation as a surrogate to lysimeter measurement

Reference crop evapotranspiration (ET _o), used to determine actual crop evapotranspiration, is often estimated from pan evaporation (EP) data. However, uncertainties in the relationship between ET _o and EP often result in unreliable estimate of crop evapotranspiration. This study investigated the relationship between measured and estimated crop evapotranspirations, ET _m and ET _e, respectively, at tillering (9–30 days after transplanting, DAT) and mid-growth (51–72 DAT) stages of a rice variety. ET _m was measured with a Marriott Tube-type Micro-lysimeter (hereafter referred to Micro-lysimeter) in a ponded rice field and ET _e was estimated from EP, which was measured by employing the US Weather Bureau Class ‘A’ Evaporation Pan (hereafter referred to Class A Evaporation Pan). A strong linear relation (r ² = 0.89) at the tillering stage and a weak relation (r ² = 0.48) at the mid-growth stage were obtained between ET _m and EP. The slope of this plot provided a pan-crop factor (K _p K _c), which was 0.81 at the tillering stage and 0.79 at the mid-growth stage. The ET _e versus ET _m relationship was also strongly linear (r ² = 0.90) at the tillering stage but weakly linear (r ² = 0.50) at the mid-growth stage. The pan-based method thus provided reliable estimates of evapotranspiration during the tillering stage of rice.     

Effect of fertilization on crop responses and solute transport for rice crop in a sub-humid and sub-tropical region

In order to increase the efficacy of water and control the losses of fertilizer, it is necessary to assess the influence of level of fertilization on crop responses, movement and balance of water and solutes from fertilizers in the root zone. With this goal, the reported study was undertaken to determine the effect of fertilization on crop responses and fertilizer solute transport in rice crop field in a sub-humid and sub-tropical region. Field experiment was conducted on rice crop (cultivar IR 36) during the years 2003, 2004, and 2005. The experiment included four fertilizer treatments comprising different levels of fertilizer application. The fertilizer treatments during the experiment were: F₁ = control with N:P₂O₅:K₂O as 0:0:0 kg ha^?1; F₂ = fertilizer application of N:P₂O₅:K₂O as 80:40:40 kg ha^?1; F₃ = fertilizer application of N:P₂O₅:K₂O as 120:60:60 kg ha^?1 and F₄ = fertilizer application of N:P₂O₅:K₂O as 160:80:80 kg ha^?1. The results of the investigation revealed that the magnitudes of crop parameters such as grain yield, straw yield, and maximum leaf area index increased with increase in fertilizer application rate. The levels of fertilization had very little effect on water loss via deep percolation and water use by the crop. The levels of fertilization had considerable effect on N leaching loss and uptake of N whereas it had no significant impact on leaching loss of water-soluble phosphorus. This indicated that PO₄-P leaching loss was very low in the soil solution as compared to nitrogen due to fixation of phosphorus in soils. The results also revealed that increase in level of fertilization increased water use efficiency considerably by increased crop yield. From the observed data of nutrient use efficiency, crop yield and environmental pollution, the fertilization rate of N:P₂O₅:K₂O as 80:40:40 kg ha^?1 (F₂) was the most suitable fertilizer treatment for rice crop among studied treatments.     

Impact of crop and nutrient management on crop growth and yield,nutrient uptake and content in rice

Paddy and Water Environment - System of rice intensification (SRI) together with appropriate nutrient management holds promise in increasing rice productivity with micronutrient enriched grains....     

两优培九单晚种植的高产特点及栽培技术

两优培九是由江苏省农科院和国家杂交水稻工程技术研究中心合作育成的两系杂交籼稻组合。2000年引入江山市试种 ,2002年全市种植面积0.3万hm2,占单晚面积的44.98 % ,预计2003年将进一步扩大种植 ,成为江山市单晚的当家品种。据两年的调查显示 ,两优培九在江山市常规栽培单产仅为550kg/667m2 ,相当于示范片中低产田产量。这说明当地多数农民并未真正掌握两优培九组合的高产特点和栽培技术 ,有必要作进一步的探讨。一、两优培九的生育期及适应性经江山市2年的试验观察认为 ,两优培九感温性强、感光性不及协优9308组合 ,早播早成熟 ,全生育期14…     

Colonization of rice fields by Nilaparvata lugens (Stål) and its control using a trap crop

Colonization of rice fields by the brown planthopper, Nilaparvata lugens (Stål) (Homoptera: Delphacidae), was monitored using yellow pan oil-water traps. In approximately 3 months, 35 788 immigrant macropters (1·0 ♂: 1·2 ♀) were caught in 512 traps installed over a 0·352 ha rice field. The trend of daily trap catches conformed closely to the number of macropters visually counted on rice hills. In sub-plots with a trap crop planted 20 days earlier than the main crop on a quarter of the total crop area, more macropters were recorded on trap-crop than on main-crop rows up to about 75 days after transplanting the main crop. In control sub-plots with one planting, more hoppers arrived on the middle than on the border rows. A blanket spray application of Perthane (0·75 kg a.i./ha) was made on the crop in control sub-plots, whereas only the trap crop was sprayed in trapped sub-plots. The combined yield in each treatment with trap crop was significantly higher than in the control treatment.     

Pattern of methane emission and water productivity under different methods of rice crop establishment

Methane (CH₄) emission and water productivity were estimated in an experiment conducted during wet (rainy) season of 2010 at the research farm of Indian Agricultural Research Institute, New Delhi, India. Treatments comprising three methods of crop establishment viz., conventional transplanting (CT), system of rice intensification (SRI) and double transplanting (DT) were laid out in randomized block design with four replications. Scented rice (Oryza sativa L) variety ‘Pusa Basmati 1401’ was transplanted in puddle field. In CT and SRI 21 and 12-day-old seedlings, respectively, were transplanted while in DT overall 45-day-old seedlings were transplanted. In CT and DT flooded conditions while in SRI saturated conditions were maintained. Results indicated that among the methods of crop establishment, CT had maximum cumulative CH₄ emission (32.33 kg ha^?1) followed by DT (29.30 kg ha^?1) and SRI (19.93 kg ha^?1). Temporal CH₄ flux fluctuated between 79.7 and 482.0 mg m^?2 day^?1 under CT; 46.0 and 315.0 mg m^?2 day^?1 in SRI and 86.7 and 467.3 mg m^?2 day^?1 in DT. Considerable temporal variations in the individual CH₄ fluxes were observed. Flux of CH₄ was generally higher in early stage of crop and peaked about 21 days after transplanting coinciding with tillering stage of crop. CH₄ flux declined gradually from 75 days after transplanting and stabilized at the harvest stage of rice in all the three methods of transplanting. Global warming potential was highest in CT (807.4 kg CO₂ ha^?1) and lowest in SRI (498.25 kg CO₂ ha^?1). However, a reverse trend was observed with carbon efficiency ratio. The water savings to the extent of six irrigations was recorded in SRI over CT. A saving of 27.4 % irrigation water and 18.5 % total water was recorded in SRI over CT while the corresponding values of DT over CT were 14.5 and 9.8 %. Water productivity of SRI (3.56 kg/ha mm) was significantly higher as compared to DT (2.87 kg/ha mm) and CT (2.61 kg/ha mm).     

Flood damage assessment on rice crop in the Stung Sen River Basin of Cambodia

Paddy and Water Environment - In Cambodia, rice production is important for the majority of rural populations as the main source of income. However, historical extreme flood events, especially the...     

Water use in rice crop through different methods of irrigation in a sodic soil

Sodic soils are characterized by high exchangeable sodium on exchange sites, soil pH greater than 8.5, relatively low electrical conductivity, low infiltration rate and dispersed clay. These characteristics restrict the capacity of soil to absorb water, resulting in poor infiltration. Evidently, these soils require application of irrigation water at shorter intervals for crop production. Thus, irrigation strategy for sodic soils differs from that of normal soils. An experiment to determine the suitable irrigation strategy along with methods of application namely: surface (farmer’s practice), sprinkler (double nozzle impact sprinkler), and low-energy water application device (LEWA) were initiated in the year 2012 for rice crop. Irrigation depths of 6 cm in case of surface method and 4 cm in case of sprinkler and LEWA methods were applied at each irrigation event. The irrigation events for rice were scheduled at 2-DAD (days after the disappearance of the ponded water), 3-DAD, and 4-DAD through surface method, and at daily, 1- and 2-day intervals (after initial ponding disappeared) by sprinkler and LEWA methods. Sprinkler and LEWA methods resulted in highest rice yield of 4.4 t ha^?1 in irrigated plots at the 2-day interval which was at par with the highest yielding surface-irrigated plot scheduled at 2-DAD. At the same time, irrigation strategy of 2-day interval through sprinkler and LEWA methods registered water saving to the extent of 30–40% over 2-DAD under surface irrigation method. Results revealed that there could be substantial saving of water and energy (electricity and diesel) through the use of sprinkling devices for irrigating rice under sodic soil environments.     

Effects of nitrogen input and climate trends on provincial rice yields in China between 1961 and 2003: quantitative evaluation using a crop model

Paddy and Water Environment - Analyses of the technological and climatic factors that influence regional yield can provide insights into how production systems can be improved in the future. We...     

Soil fertility and establishment potential of inoculated cyanobacteria in rice crop grown under non-flooded conditions

An investigation was undertaken using a combination of microbiological and DNA-based approaches to evaluate combinations of two/three/four cyanobacterial strains (BF1 Anabaena torulosa; BF2, Nostoc carneum; BF3, Nostoc piscinale; BF4, Anabaena doliolum), using a novel vermicompost-based carrier, for their promise as inoculants in rice crop. The crop was maintained under 60% WHC through intermittent irrigation. Selected combinations (BF1 + 2 + 3; BF1 + 2 + 4; BF1 + 3 + 4) showed a consistent trend regarding their superiority over other treatments in terms of plant growth promotion and soil microbiological parameters. Microscopic examination of soil enrichment cultures raised from the treatments revealed their comparative abundance over native flora. A significant enhancement in terms of soil microbial biomass carbon and humus content was also recorded in these treatments. The soil enzymatic profile of the inoculated treatments involving FDA, dehydrogenase, acid phosphates, alkaline phosphatase, aryl esterase and β-glucosidase also revealed the promise of the inoculated strains. 16SrDNA sequencing, followed by BLAST analyses provided valuable information regarding the establishment of Anabaena strains. RFLP analyses of the 16SrDNA sequences of soil DNA and phylogenetic analyses vis a vis sequences of the inoculated cyanobacterial strains revealed the promise of treatments ?BF1 + 2 + 3, BF1 + 2 + 4 and BF1 + 3 + 4. Panicle weight (yield attribute) was statistically at par with the fertilizer controls 1/2N + PK and significantly higher than 1/3N + PK. To our knowledge, this represents a first report on evaluating the establishment of cyanobacterial inoculants in rice crop grown under non-flooded conditions (or intermittent irrigation) using a combination of agronomic, microbiological and soil DNA related attributes.     

Modeling the dependence of the crop calendar for rain-fed rice on precipitation in Northeast Thailand

Rain-fed lowlands are major agricultural ecosystems used for rice production in Northeast Thailand. Developing a tool to assess the effects of variable water conditions on the regional scale yield is also important to predict the effects of climate change on food supply. To estimate regional yields, we need a simple but accurate measure of the crop calendar (i.e., the distribution of planting dates), which has a strong influence on grain yield. In this article, we modeled the dependence of the crop calendar on rainfall patterns based on a survey of the region’s farmers as a part of an effort to provide a stronger basis for regional yield estimates. Our survey, conducted in 11 provinces for 2 years, confirmed the existence of large windows for sowing and transplanting versus narrow windows for heading and harvesting for rain-fed lowland rice culture in all the provinces. Variable water, soil, and toposequential conditions in the paddy fields were responsible for the large sowing and transplanting windows, whereas the use of photoperiod-sensitive varieties explained the narrow windows for heading and harvesting. The crop calendar was well expressed as a function of cumulative precipitation from June onward. When the crop calendar model was combined with a simple phenology-based model that uses growing degree-days adjusted by a day-length factor, we could estimate the rice crop calendar under rain-fed lowland conditions with acceptable accuracy. The model described in this article will be combined with a crop growth model to improve regional yield estimates for rain-fed lowland rice.     

Toward the development of a weather index insurance for rice farmers in the coastal region of Myanmar

Paddy and Water Environment - Climate change is expected to exacerbate damage to agricultural production from natural disasters. Examination of measures to adapt to the damage represents an urgent...     

Raised and sunken bed land configuration for crop diversification and crop and water productivity enhancement in rice paddies of the north eastern region of India

Paddy and Water Environment - The crop and water productivity (WP) of monocropped rice in lowland of north-eastern region of India is low mainly due to cultivation of long duration variety, meagre...     

Effects on rice plant morphology and physiology of water and associated management practices of the system of rice intensification and their implications for crop performance

Field experiments were conducted in Bhubaneswar, Orissa, India, during the dry season (January–May) in 2008 and 2009 to investigate whether practices of the System of Rice Intensification (SRI), including alternate wetting and drying (AWD) during the vegetative stage of plant growth, could improve rice plants’ morphology and physiology and what would be their impact on resulting crop performance, compared with currently recommended scientific management practices (SMP), including continuous flooding (CF) of paddies. With SRI practices, grain yield was increased by 48% in these trials at the same time, there was an average water saving of 22% compared with inundated SMP rice. Water productivity with AWD-SRI management practices was almost doubled (0.68 g l⁻¹) compared to CF-SMP (0.36 g l⁻¹). Significant improvements were observed in the morphology of SRI plants in terms of root growth, plant/culm height, tiller number per hill, tiller perimeter, leaf size and number, leaf area index (LAI), specific leaf weight (SLW), and open canopy structure. These phenotypic improvements of the AWD-SRI crop were accompanied by physiological changes: greater xylem exudation rate, crop growth rate, mean leaf elongation rate (LER), and higher light interception by the canopy compared to rice plants grown under CF-SMP. SRI plants showed delayed leaf senescence and greater light utilization, and they maintained higher photosynthetic rates during reproductive and grain-filling stages. This was responsible for improvement in yield-contributing characteristics and higher grain yield than from flooded rice with SMP. We conclude that SRI practices with AWD improve rice plants’ morphology, and this benefits physiological processes that result in higher grain yield and water productivity.