Nitrogen Dynamics in Lowland Rice as Affected by Crop Establishment and Nitrogen Management

Abstract

Information on the dynamics of nitrogen as influenced by crop establishment method and N management strategy is meager, but such information is necessary in optimizing nitrogen input for lowland rice (Oryza sativa L.). A field experiment was conducted at the experimental farm of the International Rice Research Institute (IRRI), Philippines, during the wet and dry seasons of 2003 and 2004 to evaluate the effects of crop establishment and nitrogen management strategies for lowland rice on the dynamics of mineral N. The experiment was laid out in a split-plot design with four crop establishment methods as main plots and two N management techniques as subplots with three replications. Zero-N fertilizer (N-omission) micro-plots were embedded in each plot. Crop establishment method did not significantly influence uptake of indigenous mineral N during the wet (44-55 kg ha-1) and dry (43-50 kg ha-1) seasons. Apparently, NH4+-N and NO3～-N accumulated in the top 20-cm layer of the soil during the wet season, resulting in relatively high initial N during the dry season. Crop establishment and N management strategies did not influence crop removal of N during a one-year period. Actual N balance across crop establishment methods during the one-year period ranged from 10 to 16 kg ha-1, whereas the apparent N balance ranged from 45 to 99 kg ha-1. A fertilizer recommendation should be developed based on the actual N balance along with the assessment of crop N requirement for a given yield potential.     

Rice establishment method affects nitrogen use and crop production of rice–legume systems in drought-prone eastern India

The inclusion of grain legumes in rainfed lowland rice farming systems provides an opportunity to increase food production, household income, and human nutrition of impoverished rice farmers in Asia. We examined the effect of rice establishment method on the performance of wet season rice (Oryza sativa L.) and post-rice crops of either chickpea (Cicer arietinum L.) or moong [Vigna radiata (L.) Wilczek] on an Udic Haplustalf in the drought-prone, rainfed lowlands of eastern India. Rice was either direct seeded in lines on moist soil immediately after the onset of wet season rain or transplanted after sufficient rainwater accumulated for soil submergence. Crop establishment method had no effect on rice performance in a season (2001) with normal rainfall. In a drought season (2002), direct seeding resulted in mean rice grain yield of 2.3 t ha⁻¹, whereas the transplanted rice crop failed. The agronomic efficiency of N fertilizer applied to direct-seeded rice was comparable for the 2 years (18 and 24 kg grain per kg N applied). Topsoil inorganic N was markedly higher following chickpea and moong than following a post-rice fallow. Direct-seeded rice had higher yield and accumulation of N following a post-rice legume than following fallow, but transplanted rice derived no such benefit from the legume. Direct-seeded rice was established 1–2 months before transplanted rice, and direct-seeded rice matured before transplanted rice by 8 days in the favorable season and by 26 days in the drought season. The soil nitrate present after legumes and fallow rapidly disappeared, presumably by denitrification, following the onset of rains and soil flooding prior to transplanting. A portion of this accumulated soil nitrate was taken up by the direct-seeded rice before it could be lost. But transplanted rice did not benefit from this inorganic N derived from legumes because virtually all soil nitrate was lost before transplanting. Direct seeding of rice ensured better use of residual and applied N, reduced risk due to drought, and favored intensification with post-rice legumes in drought-prone lowland systems.     

Seed Priming Improves Agronomic Trait Performance under Flooding and Non-flooding Conditions in Rice with QTL SUB1

Farmers in South East Asia are adopting rice crop establishment methods from transplanting to direct wet or dry seeding as it requires less labour and time and comparatively less energy than transplanting.In contrast to irrigated condition,in rainfed lowland,direct seeding is a common practice.Early flooding controls weeds but decreases seedling establishment in direct seeded rice.Anaerobic germination is an important trait to counteract damages caused by early flooding.Management options which can help in crop establishment and improve crop growth under flooding might remove the constraints related to direct seeding.The investigation was carried out with two near isogenic lines Swarna and SwarnaSub1.Swarna-Sub1 is tolerant to submergence whereas Swarna is susceptible.Seed priming was done with water and 2% Jamun(Syzygium cumini) leaf extract,and it improved seedling establishment under flooding.Acceleration of growth occurred due to seed pretreatment,which resulted longer seedling and greater accumulation of biomass.Seed priming greatly hastened the activities of total amylase and alcohol dehydrogenase in Swarna-Sub1 than in Swarna.Swarna-Sub1 outperformed Swarna when the plants were cultivated under flooding.Weed biomass decreased significantly under flooding compared to non-flooding conditions.Seed priming had positive effects on yield and yield attributing parameters both under non-flooding and early flooding conditions.     

The implications of land preparation, crop establishment method and weed management on rice yield variation in the rice-wheat system in the Indo-Gangetic plains

The implications of adopting alternative seeding methods for rice and wheat establishment were examined at three geographically separate sites in the rice-wheat system of the Indo-Gangetic plains, across northern India. Rice yields in cultivated plots, established by either wet or dry seeding methods, were evaluated in comparison to yields from zero-tillage plots and under conventional transplanting methods. In the same trials, the effects of crop establishment methods in wheat were assessed both on wheat yields and rice yields. Rice crop establishment methods markedly influenced the emerging weed flora and attainable yields were measured in relation to intensity of weed management. Over four years, average rice grain yields in the absence of weed competition were greatest (6.56 t ha⁻¹) under wet seeding (sowing pre-germinated rice seed on puddled soil), and similar to those from transplanted rice (6.17 t ha⁻¹) into puddled soil, and dry seeded rice after dry soil tillage (6.15 t ha⁻¹). Lowest yields were observed from dry seeded rice sown without tillage (5.44 t ha⁻¹). Rice yield losses due to uncontrolled weed growth were least in transplanted rice (12%) but otherwise large (c. 85%) where rice had been sown to dry cultivated fields or to puddled soil, rising to 98% in dry seeded rice sown without soil tillage. Weed competition reduced multiple rice yield components, and weed biomass in wet seeded rice was six-fold greater that in rice transplanted into puddled soil and twice as much again in dry seeded rice sown either after dry tillage or without tillage. Wheat grain yields were significantly higher from crops sown into tilled soil (3.89 t ha⁻¹) than those sown without tillage (3.51 t ha⁻¹), and also were elevated (5% on average) where the soil had been dry cultivated in preparation for the previous rice crops rather than puddled. The method of wheat cultivation did not influence rice yield. Soil infiltration rates in the wheat season were least where the land had been puddled for rice (1.52 mm h⁻¹), and greater where the soil had been dry-tilled (2.63 mm h⁻¹) and greatest after zero-tillage (3.54 mm h⁻¹).These studies demonstrated at research managed sites across a wide geographic area, and on farmers’ fields, that yields of dry seeded rice sown after dry cultivation of soil were broadly comparable with those of transplanted rice, providing weed competition was absent. These results support the proposition that direct seeding of rice could provide an alternative to the conventional practice of transplanting, and help address rising costs and threats to sustainability in the rice-wheat rotation. Further, analysis of patterns of long-term rainfall data indicated that farmers reliant on monsoon rainfall could prepare fields for dry direct seeded rice some 30 days before they could prepare fields for either transplanting or seeding with pre-germinated seed. Dry, direct seeding of rice contributes a valuable component of an adaptive strategy to address monsoonal variability that also may advance the time of wheat establishment and yield. Whilst the results illustrate the robustness, feasibility and significant potential of direct seeded rice, they also highlight the critical nature of effective weed control in successful implementation of direct seeding systems for rice.     

水稻高产高效优质栽培研究的现状(英文)

近年来一些发达国家利用信息技术和先进知识大力发展精准农业 ,以达到改良作物表现和提高环境质量的目的。中国的农学家依据精准农业的原理并结合本国的实践 ,初步提出了水稻等作物在高产栽培条件下基本苗、施肥和灌溉的定量方法和关键指标 ,为构建具有中国特色的作物精准栽培技术体系奠定了基础。水稻直播省工节本 ,其应用面积在亚洲正逐年增加。杂草控制和倒伏问题是制约水稻直播产量及其应用面积扩大的两大因素。水稻地膜覆盖栽培近几年正在中国兴起。地膜覆盖可增温保墒、节约用水和减少氮肥损失。但地膜覆盖对环境带来的污染应引起重视。作物栽培已从单纯注重产量 ,转变为产量、优质、高效相统一 ,注重环境的保护 ,重视无公害食品、绿色食品、有机食品的开发。农业信息技术运用于作物栽培技术的研究 ,将促进栽培技术的现代化、标准化和智能化。     

川东南轻简栽培方式再生稻产量构成特征和经济效益分析

为了探明轻简栽培方式对中稻+再生稻产量构成特征和经济效益的影响,以黄华占和金农丝苗为材料,于2017年在四川泸州进行不同栽培方式(翻耕移栽、翻耕直播、免耕移栽)的大田试验,分析了中稻-再生稻干物质生产特性、产量、产量构成和经济效益.结果表明,不同栽培方式间头季稻产量差异不显著.翻耕直播头季稻产量较翻耕移栽平均增加3.5...     

不同耕作和种植方式对稻田杂草及水稻产量的影响

采用田间试验,研究了7种不同水稻耕作和种植方式[水田翻耕移栽(puddling transplanting,PT)、免耕移栽(no tillage transplanting,NTT)、水田翻耕滚筒湿播(puddling drum wet seeding,PDWS)、免耕滚筒湿播(no tillage drum wet seeding,NTDWS)、传统耕作旱穴播(conventional tillage dry drilling,CTDD)、沟垄灌溉旱穴播(furrow irrigated raised beds system dry drilling,FIRBSDD)和免耕旱穴播(no-tillage dry-drilling,NTDD)对稻田杂草和水稻产量的影响。结果表明,PT处理下水稻产量最高,杂草干物质量最低;与移栽相比,直播(direct seeded rice,DSR),包括旱直播和湿直播,杂草生长能力最强,且不管有无杂草均降低了水稻产量;直播处理因杂草使水稻减产91.4%~99.0%,而PT和NTT处理分别减产16.0%和42.0%;香附子、龙爪茅、长穗苋、珠子草和假海马齿等杂草种类在DSR处理中大量出现,但在PT处理中未出现。大田示范试验结果表明,普通水稻品种(HKR-47和IR-64)在DSR处理较PT处理减产达15.8%,但优质水稻品种(Sharbati和PB-1)在两处理间无明显差异。当前劳动力紧缺,人工插秧需要大量劳力,因此亟需开发好氧栽培(如免耕直播和机插)模式下的适宜水稻品种及其相关配套农业机械及技术。     

Increasing Production of Rainfed Lowland Rice in Drought Prone Environments

Summary

Drought is a major production constraint of rainfed lowland rice grown in Thailand and Laos. Adverse soil conditions also reduce yield. In an attempt to increase rainfed lowland rice production in these countries, a major collaborative international project was conducted during a 6-year period in the region. The objectives of the project were to quantify production constraints, determine genotypic variation in yield, and identify an effective breeding strategy. A rice simulation model was developed also and used to investigate the potential impact of strategies for genetic improvement and agronomic management.

Four major physical or biological constraints to higher production levels of rainfed lowland rice were identified, (1) the lack of standing water at the appropriate time of transplanting, (2) severe water stress that often develops at the end of the growing season, (3) low yield potential of the present cultivars, particularly in Thailand, and (4) adverse soil conditions including low pH and low soil fertility. The results of the field experiments and simulation modelling exercises showed that the influence of these constraints can be reduced and yield increased by several methods : in particular, choice of appropriate cultivars and time of sowing to match crop phenology with water availability, application of appropriate fertilizer, adoption of high yielding cultivars, adoption of direct seeding in place of the traditional transplanting system, and reduction of percolation water loss from the paddies.

A technology package currendy being investigated for the rainfed lowland rice is direct seeding early in the season, using cultivars that flower by the end of the rainy season, with application of organic or chemical fertilizer. The appropriate cultivars are early flowering and short-intermediate statured, possess high yield potential and ability to maintain favourable plant water status at flowering, and have the ability to establish well and compete against weed under direct seeding.     

Agronomic and economic evaluation of Sesbania rostrata green manure establishment in irrigated rice

Research on crop establishment methods may improve green manure performance, reduce costs, and increase the adaptability of pre-rice green manure technology in lowland rice-based cropping systems. A two-season field experiment was conducted at the International Rice Research Institute (IRRI) in Los Baños, Philippines in 1991–1992 to compare four establishment practices of Sesbania rostrata green manure (zero tillage, with tillage, relay cropping in rice for 2 or 4 weeks) with four mineral N fertilizer levels (0, 30, 60, and 90 kg urea N/ha) in an intensive irrigated lowland system with three rice crops per year. S. rostrata was grown twice a year during the 43-day dry-wet and wet-dry transition periods between the wet and dry season rice crops.

Grain yield potential and fertilizer responsiveness of rice was generally highest in the dry season. On the other hand, S. rostrata growth was more vigorous in the wet season (long-day period) than in the dry season, regardless of establishment method. Green manure N accumulation was lowest with zero tillage (30 and 90 kg N/ha in dry and wet season, respectively) and highest when it was relay-cropped for two weeks (60 and 180 kg N/ha in dry and wet season, respectively). Land preparation for Sesbania ensured best green manure stand (> 100 plants/m² vs 20–40 plants/m² at no-till establishments) but increased costs of green manuring by US$16/ha compared with other establishment methods. A quadratic response function between mineral fertilizer equivalence and green manure N indicated that up to 75 kg N/ha, lowland rice uses green manure N more efficiently than urea. Depending on season and establishment method, S. rostrata substituted for 35 to 90 kg of split-applied urea N. Benefit-cost ratios indicated that pre-rice green manure use in the wet season under the current fertilizer and labor prices in the Philippines was a less attractive economic option than mineral N fertilizer. This was true for all establishment methods. In the dry season, S. rostrata established by relay cropping gave the highest rate of return. The 2-week relay cropping of green manure with irrigated rice gave highest green manure N accumulation and rice grain yield, and may be economically viable where fertilizer prices are higher or labor costs are lower than in the Philippines.     

Evapotranspiration,irrigation water requirement,and water productivity of rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.) in the Sahelian environment

Rice is the main crop produced in the Senegal River Valley under the semiarid Sahelian climate where water resource management is critical for the resource use sustainability. However, very limited data exit on rice water use and irrigation water requirement in this water scarcity environment under climate change conditions. Understanding crop water requirements is essential for better irrigation practices, scheduling and efficient use of water. The objectives of this study were to estimate crop water use and irrigation water requirement of rice in the Senegal River Valley at Fanaye. Field experiments were conducted during the 2013 hot and dry season and wet season, and 2014 hot and dry season and wet seasons. Three nitrogen fertilizer treatments were applied to rice variety Sahel 108: 60, 120, and 180 kg N ha^?1. Rice water use was estimated by the two-step approach. Results indicated that crop actual evapotranspiration (ETa) varied from 632 to 929 mm with the highest ETa obtained during the hot and dry seasons. Irrigation water requirement varied from 863 to 1198 mm per season. Rice grain yield was function of the growing season and varied from 4.1 to 10.7 tons ha^?1 and increased with nitrogen fertilizer rate. Rice water use efficiency relative to ETa and irrigation requirements increased with nitrogen fertilizer rate while rice nitrogen use efficiency decreased with the nitrogen fertilizer rates. The results of this study can be used as a guideline for rice water use and irrigation water requirement for the irrigation design projects, consultants, universities, producers, and other operators within rice value chain in the Senegal River Valley.     

头季稻氮肥运筹对再生稻根际机能及产量的影响

[目的]再生稻是头季稻生长的延续.本研究尝试从根际微生态系统的变化来阐明机械化栽培下头季稻氮肥管理对头季-再生季水稻产量形成的影响,为再生稻高产高效栽培提供参考.[方法]以"甬优1540"为材料,通过2年的田间试验,在头季总施氮量(225.00 kg/hm2)不变的前提下,设置头季不同氮肥运筹处理,分析了机械化栽培下再...     

Productivity and resource use of direct-(drum)-seeded and transplanted rice in puddled soils in rice–rice and rice–wheat ecosystems

Conventional tilled transplanting, a widely practiced method of rice (Oryza sativa L.) establishment in puddled soils in rice–rice and rice–wheat (Triticum aestivum L.) systems in Asia, requires a large amount of labor and water, which are becoming scarce and expensive. Growing more food with the same production costs or even reduced costs and sustaining the quality of the natural resource base are a major concern. On-farm trials were conducted in Chuadanga District of Bangladesh during the wet season as monsoon rice (aman) and during the dry season as winter rice (boro) in 2006–07 to evaluate the effects of establishment methods with improved crop management on productivity, resource (land, water, and labor) use, and economic return. Rice was established by sowing in line with a drum seeder on conventional tilled puddled soils (CT-DrumR) and by transplanting in line on the day of CT-DrumR (CT-TPR1) and 30 and 35 days after CT-DrumR (CT-TPR2) in aman and boro seasons, respectively. Farmers’ usual transplanting time corresponds to the day of CT-TPR2. Grain yields in CT-DrumR and CT-TPR2 were similar but the crop occupied the main field 22–24 days longer in CT-DrumR than in CT-TPR2, resulting in lower productivity (45 kg grain ha⁻¹ day⁻¹ vs. 55 kg grain ha⁻¹ day⁻¹) in both seasons. Drum-seeded rice matured earlier by 8 and 11 days, received 12% and 6% less irrigation water, saved 19 and 24 person-days ha⁻¹, and gave higher gross margins of 6% and 4% but input costs increased by 20% and 12% than CT-TPR2 in aman and boro seasons, respectively. There is a need to examine these benefits of drum-seeded rice in relation to the feasibility of adoption by farmers.     

Influence of Crop Nutrition on Grain Yield, Seed Quality and Water Productivity under Two Rice Cultivation Systems

The system of rice intensification (SRI) is reported to have advantages like lower seed requirement,less pest attack,shorter crop duration,higher water use efficiency and the ability to withstand higher degree of moisture stress than traditional method of rice cultivation.With this background,SRI was compared with traditional transplanting technique at Indian Agricultural Research Institute,New Delhi,India during two wet seasons (2009-2011).In the experiment laid out in a factorial randomized block design,two methods of rice cultivation [conventional transplanting (CT) and SRI] and two rice varieties (Pusa Basmati 1 and Pusa 44) were used under seven crop nutrition treatments,viz.T 1,120 kg/hm2 N,26.2 kg/hm2 P and 33 kg/hm2 K;T 2,20 t/hm2 farmyard manure (FYM);T 3,10 t/hm2 FYM+ 60 kg/hm2 N;T 4,5 t/hm2 FYM+ 90 kg/hm2 N;T 5,5 t/hm2 FYM+ 60 kg/hm2 N+ 1.5 kg/hm2 blue green algae (BGA);T 6,5 t/hm2 FYM+ 60 kg/hm2 N+ 1.0 t/hm2 Azolla,and T 7,N 0 P 0 K 0 (control,no NPK application) to study the effect on seed quality,yield and water use.In SRI,soil was kept at saturated moisture condition throughout vegetative phase and thin layer of water (2-3 cm) was maintained during the reproductive phase of rice,however,in CT,standing water was maintained in crop growing season.Results revealed that CT and SRI gave statistically at par grain yield but straw yield was significantly higher in CT as compared to SRI.Seed quality was superior in SRI as compared to CT.Integrated nutrient management (INM) resulted in higher plant height with longer leaves than chemical fertilizer alone in both the rice varieties.Grain yield attributes such as number of effective tillers per hill,panicle length and panicle weight of rice in both the varieties were significantly higher in INM as compared to chemical fertilizer alone.Grain yields of both the varieties were the highest in INM followed by the recommended doses of chemical fertilizer.The grain yield and its attributes of Pusa 44 were significantly higher than those of Pusa Basmati 1.The seed quality parameters like germination rate and vigor index as well as N uptake and soil organic carbon content were higher in INM than those in chemical fertilizer alone.CT rice used higher amount of water than SRI,with water saving of 37.6% to 34.5% in SRI.Significantly higher water productivity was recorded in SRI as compared to CT rice.     

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

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

Effects of planting date and variety on flooded rice production in the deepwater area of Thailand

Crop management plays an important role in the transition from a deepwater rice to a flooded rice production system but information about optimum management strategies are currently lacking. The goal of this study was to determine the effect of planting date and variety on flooded rice production in the deepwater area of Thailand. Two experiments were conducted at the Bang Taen His Majesty Private Development Project in 2009 and 2010 to represent conditions prior to flooding (early rainy season) and after flooding (dry season). The early rainy season crop covered the period from May to October 2009, while the dry season crop covered the period from November 2009 to April 2010. The experimental design was a split plot with four main plots and three sub plots replicated four times. The treatments for the main plot were various planting dates, while the treatments for the sub plots were rice varieties. The dates of the critical developmental phases of rice were recorded and biomass was sampled during the growing period. The collected data were statistically analyzed using ANOVA and treatment means were compared to identify the appropriate plating date and the best variety for the area. The highest average yield was obtained for variety PSL2 across transplanting dates from June 19 to July 23, with an average yield of 3898 kg ha⁻¹. The dry season crop showed that both biomass and yield were affected by the interaction between planting date and variety. The highest yield was obtained for variety PTT1 transplanted on November 9. The research showed that the variety PSL2 is the most suitable variety for early rainy season production with a transplanting date ranging from June 19 to July 23, while the variety PTT1 planted on November 9 was the best management practice for the dry season crop. However, a high yielding flooded rice variety that has a short growth duration is still needed for this area.     

Changes in Nutritive Value of Italian Ryegrass (Lolium multiflorum Lam.) during Overwintering Period

Abstract

In recent years, water and labor shortage in Southeast Asia is driving the farmers towards dry-seeded rice systems. Weed infestation is a serious threat for adoption of these systems. A study was conducted in the wet and dry seasons to evaluate the performance of 10 elite “Green Super Rice” (a recently named group of rice genotypes bred for unfavorable marginal environments) genotypes at two different weed infestation levels (partial and moderate weed control) under dry-seeded conditions. Average yield loss due to weed competition in the partial weed control treatment ranged from 12 – 57% in the wet season and 2 – 23% in the dry season. In the partial weed control plots, the drought pyramiding genotype IR83140-B-11-B performed well, resulting in 2850 and 4610 kg ha^–1 of yield in the wet and dry seasons, respectively. The yield loss of this genotype in the partial weed control plots relative to the moderate weed control plots was only 21% in the wet season and 10% in the dry season. Results clearly showed that grain yield in different genotypes were positively correlated with leaf area at an early stage of the crop. The study also found negative and linear correlation between grain yield and weed biomass at harvest, demonstrating the importance of weeds in dry-seeded rice systems. The study suggested that genotypes with a larger leaf area could be integrated with other weed management strategies to achieve sustainable weed control in dry-seeded rice systems.     

Nitrogen and water effects on wheat yield in a Mediterranean-type climate: I. Growth,water-use and nitrogen accumulation

Available soil water is the principal factor that limits the yield potential of wheat (Triticum aestivum L.) and its response to nitrogen (N) under Mediterranean climatic conditions. We examined wheat yield, N fertilizer uptake, and water use for two seasons (1991/1992 and 1992/1993) with total seasonal rainfall of 323 and 275 mm, respectively. In addition to natural rainfall, supplemental irrigation at various rates (1/3, 2/3 and full irrigation) was also considered in assessing these parameters and their interactive effects. Grain yield and dry matter accumulation and N uptake varied between years, mainly due to rainfall and sowing date. Yields were increased by irrigation and N fertilization, with a greater response to N in 1991/1992 and to irrigation in the relatively drier 1992/1993 season. Most fertilizer N was taken up from tillering to anthesis; then it either stabilized or slightly declined, while soil N contributed further to plant N uptake. Compared to rain-fed conditions, more soil and fertilizer N was utilized by the irrigated crop, particularly in 1992/1993. In both years, grain N represented 60% of N accumulated at anthesis under rain-fed conditions, compared to 80% under irrigation. Fertilization and irrigation increased water-use efficiency, particularly under drier conditions. Thus, supplemental irrigation, applied at a sensitive growth stage, would be a valuable management practice for improving yield, water-use efficiency and crop N uptake under the dry conditions of a Mediterranean climate. Given the potential of both irrigation and N to increase output in dry areas, the amounts of both inputs are dictated by rainfall in any one year.     

不同育秧方式下播种量和插秧机具对机插稻氮素利用和产量的影响

【目的】氮素的吸收利用决定着水稻物质积累和产量的形成。随着农村劳动力的减少,机插稻迅速发展, 但针对机插稻育秧环节与插秧机具融合对机插稻氮素吸收利用特征影响的研究较少。以机插稻农机农艺首要融合点“育秧-机插”关键环节为研究对象,探究育秧方式配合不同插秧机具对机插稻氮素吸收利用的影响。【方法】以杂交籼稻F优498为试验材料,采用三因素随机区组试验,设置2种育秧方式：营养土育秧和稀泥育秧;3个播种量：65 g/盘,85 g/盘,105 g/盘;2种插秧机具：4行手扶式插秧机,6行乘坐式高速插秧机。【结果】育秧方式、播种量以及插秧机具对机插稻结实期不同营养器官氮素吸收转运、剑叶SPAD值以及氮素收获指数、氮素稻谷生产效率与产量影响显著或极显著,且互作效应显著或极显著。营养土育秧处理下机插稻氮素积累以及氮素利用效率较稀泥育秧优势明显,植株各器官氮素转运量、转运率、贡献率以及穗部氮素增加量均一定程度高于稀泥育秧处理,平均提高了21.12%、15.20%、10.03%、6.45%;随着播种量的增加,机插稻稻谷产量、结实期氮素吸收转运量、氮素干物质生产效率以及氮肥偏生产力呈先上升后下降的趋势,尤其播种量为85 g/盘时机插稻成熟期植株中氮素的积累量相较于65 g/盘、105 g/盘播量平均增加了16.19%,28.14%;6行乘坐式高速插秧机处理下机插稻产量以及构成因素、结实期干物质量、植株氮素吸收量和转运量、氮干物质生产效率以及氮肥偏生产力显著高于4行手扶式插秧机。【结论】综合氮素积累量和氮素转运量、机插稻结实期穗部氮素积累量、产量及其构成因素考虑,运用营养土育秧,播量85 g/盘配合6行乘坐式高速插秧机能有效提高机插稻氮素吸收利用,促进产量的形成。     

机插密度与氮肥运筹对中嘉早17产量形成及氮肥利用率的影响

针对长江流域双季稻机插秧发展缓慢的问题,以常规早稻品种中嘉早17为材料,在大田条件下研究了栽插密度与氮肥用量对机插双季稻产量的影响。结果表明,机插双季稻产量并未随栽插密度增加而显著增加。以高密(36.4万穴/hm²)+高氮(施纯氮量早稻175.5 kg/hm²,晚稻189 kg/hm²)处理产量最高,其中,早稻为7.80 t/hm²,晚稻为9.05 t/hm²,但与高密+中氮(施纯氮量早稻110 kg/hm²,晚稻140 kg/hm²)处理产量差异不显著,且栽插密度和施氮量间互作效应不显著。氮肥利用率随氮肥用量增加而下降,随栽插密度增加而提高。其中,氮肥吸收利用率中氮比高氮平均增加13.26%,高密度比低密度平均增加17.53%。由此可见,提高栽插密度,减少氮肥用量,既可通过大幅增加有效穗以实现高产,又能显著提高氮肥利用率。少氮密植可作为长江流域机插双季稻高产高效栽培的关键技术。     

播种方式和播种密度对杂交籼稻机插秧节本增效的研究

【目的】探索机插杂交籼稻稀播育秧秧苗生长特性、栽插质量、产量与效益特点。【方法】以F优498和Ⅱ优498的种子为材料开发并优选条播器后,采用两因素裂区设计,播种方式为主区,播种量为副区。【结果】条播播种均匀度优势明显,24行条播规格效果最佳。播种14 d后,秧苗开始产生分蘖芽,播后17至23 d是分蘖芽发生速率最快时期。随播种密度的增加,成苗率、干物质积累量、根冠比、秧苗充实度、N积累量、分蘖芽发生率、发根力、漏插率都呈降低趋势,同时有效穗数增加,每穗粒数减少,产量先增加后降低。条播相对于散播,秧苗整体素质较好,易形成壮秧,产量较高。【结论】投入与产出综合分析,采用条播方式,播种密度为50 g/盘时,秧苗群体密度和个体优势之间能得到较好的协调,产投比最高。