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.     

Investigating early vigour in upland rice (Oryza sativa L.): Part I. Seedling growth and grain yield in competition with weeds

This paper is the first of a series that investigates whether new cropping systems with permanent raised beds (PRBs) or Flat land could be successfully used to increase farmers’ incomes from rainfed crops in Lombok in Eastern Indonesia. This paper discusses the rice phase of the cropping system. Low grain yields of dry-seeded rice (Oryza sativa) grown on Flat land on Vertisols in the rainfed region of southern Lombok, Eastern Indonesia, are probably mainly due to (a) erratic rainfall (870–1220 mm/yr), with water often limiting at sensitive growth stages, (b) consistently high temperatures (average maximum = 31 °C), and (c) low solar radiation. Farmers are therefore poor, and labour is hard and costly, as all operations are manual. Two replicated field experiments were run at Wakan (annual rainfall = 868 mm) and Kawo (1215 mm) for 3 years (2001/2002 to 2003/2004) on Vertisols in southern Lombok. Dry-seeded rice was grown in 4 treatments with or without manual tillage on (a) PRBs, 1.2 m wide, 200 mm high, separated by furrows 300 mm wide, 200 mm deep, with no rice sown in the well-graded furrows, and (b) well-graded Flat land. Excess surface water was harvested from each treatment and used for irrigation after the vegetative stage of the rice. All operations were manual. There were no differences between treatments in grain yield of rice (mean grain yield = 681 g/m²) which could be partly explained by total number of tillers/hill and mean panicle length, but not number of productive tillers/hill, plant height or weight of 1000 grains. When the data from both treatments on PRBs and from both treatments on Flat land, each year at each site were analysed, there were also no differences in grain yield of rice (g/m²). When rainfall in the wet season up to harvest was over 1000 mm (Year 2; Wakan, Kawo), or plants were water-stressed during crop establishment (Year 1; Wakan) or during grain-fill (Year 3: Kawo), there were significant differences in grain yield (g/1.5 m²) between treatments; generally the grain yield (g/1.5 m²) on PRBs with or without tillage was less than that on Flat land with or without tillage. However, when the data from both treatments on PRBs and from both treatments on Flat land, each year at each site, were analysed, the greater grain yield of dry-seeded rice on Flat land (mean yield 1 092 g/1.5 m²) than that on PRBs (mean 815 g/1.5 m²) was mainly because there were 25% more plants on Flat land. Overall when the data in the 2 outer rows and the 2 inner rows on PRBs were each combined, there was a higher number of productive tillers in the combined outer rows (mean 20.7 tillers/hill) compared with that in the combined inner rows on each PRB (mean 18.2 tillers/hill). However, there were no differences in grain yield between combined rows (mean 142 g/m row). Hence with a gap of 500 mm (the distance between the outer rows of plants on adjacent raised beds), plants did not compensate in grain yield for missing plants in furrows. This suggests that rice (a) also sown in furrows, or (b) sown in 7 rows with narrower row-spacing, or (c) sown in 6 rows with slightly wider row-spacing, and narrower gap between outer rows on adjacent beds, may further increase grain yield (g/1.5 m²) in this system of PRBs. The growth and the grain yield (y in g/m²) of rainfed rice (with rainfall on-site the only source of water for irrigation) depended mainly on the rainfall (x in mm) in the wet season up to harvest (due either to site or year) with y = 1.1x − 308; r² = 0.54; p < 0.005. However, 280 mm (i.e. 32%) of the rainfall was not directly used to produce grain (i.e. when y = 0 g/m²). Manual tillage did not affect growth and grain yield of rice (g/m²; g/1.5 m²), either on PRB or on Flat land.     

Yield formation and tillering dynamics of direct-seeded rice in flooded and nonflooded soils in the Huai River Basin of China

Water shortage in the Huai River Basin prompts farmers to adopt water-saving technologies such as direct-seeded nonflooded or aerobic rice. Different cultivation practices impact on tiller growth and development. Improved insight into tiller dynamics is needed to increase yield in these production systems. We conducted field experiments with four direct-seeded rice varieties under flooded and nonflooded conditions in Mengcheng county, Anhui province, in 2005–2006. The soil water content in the nonflooded treatment varied between saturation and field capacity. Yields in nonflooded soil ranged from 3.6 to 4.7 t ha⁻¹, and did not differ significantly from yields in flooded soil that ranged from 3.6 to 5.1 t ha⁻¹. Variety had a significant effect on biomass, yield, panicle number, spikelet number, grain weight, and grain filling percentage. Panicle number was the main factor limiting yield, resulting from a low tiller emergence frequency and a low fraction of productive tillers in both the flooded and the nonflooded soils. On average, the panicle number was 159–232 m⁻², including 34–167 productive tillers per m² for all the varieties under the two water regimes. The contribution of productive tillers to yield varied between 7% and 47%. There were two peaks of tillers that contributed to yield, one at the low (4th or 5th) and one at the high (10th or 11th) phytomer orders. Frequencies of tiller emergence at most phytomer orders were higher in the flooded soil than in the nonflooded soil. There were no significant differences in frequencies of productive tiller emergence and contributions to yield from tillers between the soil water regimes for three of the four tested varieties. To increase yield in direct-seeded nonflooded rice production systems, both the tiller emergence frequency and the fraction of productive tillers should increase through breeding, improved crop management, or a combination.     

Rice responses to soil management in a rice-based cropping system in the semi-arid tropics of southern Lombok,Eastern Indonesia

This paper is the first of a series that investigates whether new cropping systems with permanent raised beds (PRBs) or Flat land could be successfully used to increase farmers’ incomes from rainfed crops in Lombok in Eastern Indonesia. This paper discusses the rice phase of the cropping system. Low grain yields of dry-seeded rice (Oryza sativa) grown on Flat land on Vertisols in the rainfed region of southern Lombok, Eastern Indonesia, are probably mainly due to (a) erratic rainfall (870–1220 mm/yr), with water often limiting at sensitive growth stages, (b) consistently high temperatures (average maximum = 31 °C), and (c) low solar radiation. Farmers are therefore poor, and labour is hard and costly, as all operations are manual. Two replicated field experiments were run at Wakan (annual rainfall = 868 mm) and Kawo (1215 mm) for 3 years (2001/2002 to 2003/2004) on Vertisols in southern Lombok. Dry-seeded rice was grown in 4 treatments with or without manual tillage on (a) PRBs, 1.2 m wide, 200 mm high, separated by furrows 300 mm wide, 200 mm deep, with no rice sown in the well-graded furrows, and (b) well-graded Flat land. Excess surface water was harvested from each treatment and used for irrigation after the vegetative stage of the rice. All operations were manual. There were no differences between treatments in grain yield of rice (mean grain yield = 681 g/m²) which could be partly explained by total number of tillers/hill and mean panicle length, but not number of productive tillers/hill, plant height or weight of 1000 grains. When the data from both treatments on PRBs and from both treatments on Flat land, each year at each site were analysed, there were also no differences in grain yield of rice (g/m²). When rainfall in the wet season up to harvest was over 1000 mm (Year 2; Wakan, Kawo), or plants were water-stressed during crop establishment (Year 1; Wakan) or during grain-fill (Year 3: Kawo), there were significant differences in grain yield (g/1.5 m²) between treatments; generally the grain yield (g/1.5 m²) on PRBs with or without tillage was less than that on Flat land with or without tillage. However, when the data from both treatments on PRBs and from both treatments on Flat land, each year at each site, were analysed, the greater grain yield of dry-seeded rice on Flat land (mean yield 1 092 g/1.5 m²) than that on PRBs (mean 815 g/1.5 m²) was mainly because there were 25% more plants on Flat land. Overall when the data in the 2 outer rows and the 2 inner rows on PRBs were each combined, there was a higher number of productive tillers in the combined outer rows (mean 20.7 tillers/hill) compared with that in the combined inner rows on each PRB (mean 18.2 tillers/hill). However, there were no differences in grain yield between combined rows (mean 142 g/m row). Hence with a gap of 500 mm (the distance between the outer rows of plants on adjacent raised beds), plants did not compensate in grain yield for missing plants in furrows. This suggests that rice (a) also sown in furrows, or (b) sown in 7 rows with narrower row-spacing, or (c) sown in 6 rows with slightly wider row-spacing, and narrower gap between outer rows on adjacent beds, may further increase grain yield (g/1.5 m²) in this system of PRBs. The growth and the grain yield (y in g/m²) of rainfed rice (with rainfall on-site the only source of water for irrigation) depended mainly on the rainfall (x in mm) in the wet season up to harvest (due either to site or year) with y = 1.1x − 308; r² = 0.54; p < 0.005. However, 280 mm (i.e. 32%) of the rainfall was not directly used to produce grain (i.e. when y = 0 g/m²). Manual tillage did not affect growth and grain yield of rice (g/m²; g/1.5 m²), either on PRB or on Flat land.     

遮阴对重穗型杂交水稻茎秆形态特征和抗倒伏性的影响

以穗数型杂交水稻C两优华占和重穗型杂交水稻渝香203为材料,于拔节期至抽穗期设置遮阴处理,比较两种类型杂交水稻产量及产量构成要素、茎秆力学、节间长度及基部节间茎鞘充实等方面的差异,并分析其与植株抗倒伏性的关系。结果表明,较正常光照处理(CK),遮阴处理(S)显著降低渝香203产量,主要原因是其有效穗数、穗粒数和千粒重降低,C两优华占具有相同的趋势。与CK相比,遮阴显著降低了杂交水稻弯曲力矩,倒伏指数不降反升,主要原因是折断弯矩大幅降低。遮阴处理下,渝香203弯曲应力和断面模数分别降低5.1%,25.5%,C两优华占分别降低19.3%,12.6%。进一步分析发现,遮阴处理下,渝香203茎粗和壁厚分别降低9.1%、11.9%,与断面模数变化相吻合;C两优华占茎鞘充实度分别减少25.6%、14.4%,这与弯曲应力变化相吻合。表明遮阴处理减少了重穗型水稻基部节间折断弯矩,进而增加了植株倒伏风险,同时降低了产量水平。增加基部节间茎粗、壁厚,提高茎秆断面模数,是遮阴下增强水稻茎秆强度和抗倒伏性的有效途径。     

Nitrogen studies in Lolium perenne grown for seed I. Level of application

In field trials in 1971–73, perennial ryegrass cv. S23 and S24 were given up to 200 kg ha^?1 nitrogen (N) and dry weight, seed yields and seed yield components measured. Optimum levels of applied N ranged from 80 kg ha^?1, where livestock had grazed the crop in the establishment year or where residual N levels were about 70 kg ha^?1, to 120 kg ha^?1 where residual N was low. Application of more than 120 kg ha^?1 did not increase yields further because of increased lodging and increased production of vegetative tillers. Seed set was 37–55% in S24 and 25–29% in S23 and was decreased by lodging.     

The critical period for weed control in dry-seeded rice

The critical crop-weed competition period in a dry-seeded rice system is an important consideration in formulating weed management strategies. Field experiments were conducted in the summer seasons of 2012 and 2013 at the Punjab Agricultural University, Ludhiana, India, to determine the extent of yield loss in two different rice cultivars (PR 114 and PR 115) with different periods of weed interference. Twelve weed control timings were used to identify critical periods of weed competition in dry-seeded rice. PR 114, a long-duration rice cultivar (145 d) having slower initial growth than PR 115 (125 d), was more prone to yield losses. In both years, 100% yield loss was observed where weeds were not controlled throughout the season. In weed-free plots, the grain yield of PR 114 was 6.39–6.80 t ha⁻¹, for PR 115, it was 6.49–6.87 t ha⁻¹. Gompertz and logistic equations fitted to yield data in response to increasing periods of weed control and weed interference showed that, PR 114 had longer critical periods than PR 115. Critical weed-free periods to achieve 95% of weed-free yield for PR 114 was longer than for PR 115 by 31 days in 2012 and 26 days in 2013. Weed infestation also influenced the duration of critical periods. Higher weed pressure in 2012 than in 2013 increased the duration of the critical period of crop-weed competition in that year. The identification of critical crop-weed competition periods for different cultivars will facilitate improved decision-making regarding the timing of weed control and the adoption of cultivars having high weed-suppressing abilities. This will also contribute to the development of integrated weed management in dry-seeded rice systems.     

Management of complex weed flora in dry-seeded rice

Dry-seeded rice has been introduced as an alternative to puddled hand-transplanted rice in the north Indian states of Punjab and Haryana. In dry-seeded rice, weed flora tends to be more diverse and weeds emerge in several flushes during the crop growth cycle and substantial yield reductions due to weed competition are quite common. The efficacy and compatibility of tank mixtures of different herbicides for the control of diverse weed flora in dry-seeded rice was evaluated in field experiments during the summer seasons of 2012 and 2013. The tank mixture of fenoxaprop with ethoxysulfuron improved the control of Echinochloa crus-galli and Echinochloa colona by 43–69% as compared to fenoxaprop alone while the tank-mix of azimsulfuron with fenoxaprop was antagonistic and reduced the control of Leptochloa chinensis by 86% as compared to fenoxaprop alone. Addition of azimsulfuron or ethoxysulfuron to bispyribac did not improve the control of grass weeds as compared to bispyribac alone. Weed control with the mixture of bispyribac and fenoxaprop varied over the two years. In 2012, bispyribac and fenoxaprop mixture was antagonistic for the control of Dactyloctenum aegyptium, Acrachne racemose, and L. chinensis but in 2013, there was no apparent antagonism and the addition of bispyribac to fenoxaprop reduced grass weed biomass as compared to fenoxaprop alone. In 2013, there was a strong negative correlation (r = −0.95, P < 0.001) between weed dry matter at 45 days after sowing and rice grain yield. According to the linear regression, rice crop is likely to produce no grain yield when weed dry matter exceeds 400 g m⁻². Over the two seasons, fenoxaprop-ethoxysulfuron tank-mix produced similar grain yields (5.6–6.2 t ha⁻¹) to the weed-free check (5.6–7.1 t ha⁻¹). At the farmer fields, rice grain yield in the plots treated with pendimethalin followed by post-emergence bispyribac or a tank-mix of fenoxaprop + ethoxysulfuron ranged from 6.2 to 7.7 t ha⁻¹ as compared to 5.3–5.6 t ha⁻¹ in the plots treated with pendimethalin alone. The tank mixture of fenoxaprop with bispyribac needs further evaluation as this mixture has the potential to effectively control aerobic and aquatic grasses in dry-seeded rice. Single hand weeding prevented crop yield loss from weeds that escaped herbicide treatments only when it was performed within six weeks of sowing.     

不同施氮量和栽插密度下三角形强化栽培杂交稻抗倒伏性与群体质量的关系

 以杂交水稻组合Ⅱ优498为材料,在三角形强化栽培(TSRI)条件下,研究了施氮量和栽插密度对水稻群体质量及抗倒伏能力的影响,并探讨了主要群体质量指标与茎秆抗倒伏性及产量间的关系。结果表明,TSRI下,施氮量及栽插密度对水稻产量、群体质量以及茎秆基部各节间抗倒伏能力均存在显著的调控作用。施氮量为150 kg/hm2与栽插规格40 cm×40 cm配合可提高结实期叶面积指数(LAI)、群体透光率,协调茎秆基部各节间弯曲力矩与抗折弯矩,缓和高产栽培的穗粒矛盾,显著提高籽粒产量;而施氮量增加至225 kg/hm2,应适当降低栽插密度,来缓解群体质量指标的恶化,降低倒伏指数,栽插规格50 cm×50 cm为宜。相关性分析表明,不同施氮量和栽插密度下水稻群体质量指标与茎秆基部各节间抗倒伏能力显著或极显著相关;结合产量表现,尤以齐穗期、齐穗后30 d中部的群体透光率以及齐穗后30 d的根系伤流量对水稻产量及抗倒伏性影响显著。     

植物生长调节剂对再生稻头季抗倒伏能力和两季产量的影响

【目的】为了探明植物生长调节剂对再生稻头季抗倒伏能力及两季产量的影响,【方法】以佳辐占、天优华占和甬优2640为试验材料,于拔节初期叶面喷施多效唑、乙烯利和抗倒酯,研究不同植物生长调节剂对水稻头季茎秆特性、力学指标及两季产量形成的影响。【结果】甬优2640基部节间抗折力和植株抗推力最大,抗倒伏能力强;佳辐占基部节间最长,株高最高,倒伏指数高,抗倒伏能力最差;天优华占基部倒伏指数小,抗倒伏能力介于前二者中间。与喷施清水对照相比,多效唑处理植株节间长、株高、茎壁厚与对照差异较小,增加了倒3节间(N₃)茎粗和倒4节间(N₄)和N₃的抗折力,降低了N₄和N₃的倒伏指数;乙烯利处理则显著增加了N₄长度,N₃茎粗和株高,对茎壁厚没有明显影响, 增强了N₃抗折力,降低了N₃倒伏指数;抗倒酯处理缩短了N₄、倒2节间(N₂)长,降低株高,增加N₃茎粗和N₃、N₂的茎壁厚度,增强了N₄、N₃的抗折力,降低了各节间的倒伏指数。3种植物生长调节剂处理均降低了头季产量,多效唑和抗倒酯处理增加了再生季产量,乙烯利降低了再生季产量。分析产量构成因素,植物生长调节剂处理主要影响了总穗粒数,头季总穗粒数减少,再生季总穗粒数增加。天优华占和甬优2640两季总产量均较对照降低,佳辐占总产量多效唑和抗倒酯处理较对照增加,乙烯利处理较对照降低。【结论】抗倒酯处理增强了再生稻头季茎秆的抗倒伏能力,而对两季总产量无显著影响,对再生稻头季抗倒伏栽培具有现实意义。     

Influence of Oil Palm Empty Fruit Bunch Biochar on Floodwater pH and Yield Components of Rice Cultivated on Acid Sulphate Soil under Rice Intensification Practices

Abstract

Rice has a vital role in food security but the production is limited in infertile and degraded soils. Rice is cultivated on acid sulphate soil in the coastal area of Peninsular Malaysia. Soil amendment using biological charcoal (biochar) increases the soil fertility. Thus, empty fruit bunch biochar (EFBB) was applied in a pot experiment under a controlled environment using an organic system of rice intensification (SRI) practice and its effects on the floodwater pH, acid sulphate soil properties and growth performance of rice and yield of rice MR219 were preliminarily investigated. EFBB increased grain yield by 141 to 472%. Plant growth and yield parameters in EFBB amended soils were significantly higher than in soil without biochar. The number of tillers increased significantly with the increase in biochar applied; 28 tillers were produced in the control, while up to 80 tillers were produced in the plots applied 40 t ha^–1 EFBB. Moreover, the decline of Al³⁺ in flood water indicated that EFBB mitigated Al³⁺ toxicity. Soil water pH increased from 3.5 to 6 with increasing EFBB application rates. The grain yield was linearly correlated to the application rate of EFBB. This pot study demonstrates that the application of EFBB combined with organic fertilization and intermittent irrigation has the potential to improve rice yield on acid sulphate soil. Further study in the field is warranted to determine the effect of EFBB on large scale rice production.     

Grain yield responses of lowland rice varieties to increased amount of nitrogen fertilizer under tropical highland conditions in central Kenya

Tropical highland conditions in Mwea Kenya, ensure the high radiation and the large day–night temperature differences. Such conditions are generally believed to promote rice growth and yield, but the current grain yield is lower than the expectation. In the current standard N fertilizer practice in Mwea, 75 kg nitrogen (N) ha^?1 is applied in three splits at fixed timing. The effects of increases in N fertilizer amount (125, 175, and 225 kg N ha^?1) on rice growth and yield were evaluated to test the hypothesis that unachieved high rice grain yield in Mwea is due to insufficient amount of N fertilizer. Two popular lowland varieties in Mwea (Basmati 370 and BW196) and two varieties reported as high yielding in other countries (Takanari and IR72) were used. Shoot dry weight (DW) increased with increases in the amount of N fertilizer applied in three splits at fixed timing, irrespective of variety. It reached approximately 20 t ha^?1 under increased N conditions (>75 kg N ha^?1) in several cases, indicating that high biomass production could be achieved by increasing N application rate. However, the increased biomass did not increase grain yield, due to decreased grain filling under high N conditions in all varieties. Thus, N amounts above 75 kg ha^?1 were ineffective for increasing grain yields in Mwea, where N fertilizer was applied in three splits at fixed timing. Increasing influence of low temperature under high N conditions may be one of the reasons for the decreased grain filling in Mwea.     

Growth behavior,productivity, leaf rolling,and soil cracks on transplanted rice in response to enforce surface drainage

Intermittent and prolonged dry spell during growth of transplanted rice is an important abiotic problem in north eastern region (NER). However, the productivity of rice in the region is very low, and this is mainly associated with reduced plant population, growth, and yield attributes with lower relative water content and leaf rolling with formation of soil cracks by erratic and aberrant rainfall. Keeping this in view, a field experiment on transplanted rice was conducted during two consecutive years 2011 and 2012 at NER of India, to evaluate the imposition of forced surface drainage (SD) at various growth stages (continuous drainage, SD at tillering, SD at panicle initiation, SD at booting, SD at flowering, SD at milking, and 15 days intermittent SD) and was compared with continuous flooding on growth and yield attributes, yield, relative water content, leaf rolling, and formation of soil cracks. Results revealed that continuous flooding has significant (p < 0.05) improved the plant population, growth and yield parameters, rice grain yield (3,406.7 kg ha^?1) and straw yield (4,683.3 kg ha^?1), relative water content maintained >90 %, no leaf roll, and soil crack. However, imposition of SD at tillering has lower tillers hill^?1, but yield was compensated by improvement in yield attributes. As per the availability of water, growers of the region can utilize the water for scheduling of water and most critical stages can be avoided by moisture stress to obtain higher productivity.     

有序摆抛栽对超级稻植株抗倒伏能力的影响

以粳型超级稻武运粳24和南粳44为试材,设置摆栽、点抛和撒抛三种抛栽方式,并以机插为对照,从茎秆抗折力、茎秆壁厚、节间长度、粗度、干质量等方面系统研究了有序摆抛稻的茎秆特性及其抗倒伏能力,结果如下:1)超级稻不同抛栽方式间抗倒伏能力差异显著,茎秆倒伏指数不同抛栽方式间表现为摆栽点抛撒抛、机插,基部节间抗折力、弯曲力矩和抗倒伏能力均表现为摆栽点抛撒抛、机插。就各抛栽方式下不同连孔处理而言,基部N1节间倒伏指数差异不显著,N2、N3、N4抗倒伏能力表现为2连孔、3连孔单孔。2)有序摆抛栽水稻相对重心高度稍低,成熟期茎鞘干物质量大,单穗干质量大,尤其2连孔和3连孔植株优势明显。不同抛栽方式间基部节间粗度、壁厚、节间质量和单位干质量表现为摆栽点抛撒抛,不同连孔处理间为2连孔3连孔单孔。除基部第1节间外,节间长度在抛栽方式间表现为摆栽点抛撒抛的趋势,不同连孔节间表现为2连孔、3连孔单孔的趋势。2连孔、3连孔钵苗有序摆抛在高产条件下稻株茎秆粗壮,节间短粗,节间壁厚,茎秆单位节间重,基部节间抗折力大,抗倒伏能力强,是一种利于提高水稻抗倒能力的新型水稻轻简高产栽培方式。     

Influence of rice varieties,nitrogen management and planting methods on methane emission and water productivity

A field experiment was conducted during rainy seasons of 2009 and 2010 at New Delhi, India to study the influence of varieties and integrated nitrogen management (INM) on methane (CH₄) emission and water productivity under flooded transplanted (FT) and aerobic rice (AR) cultivation. The treatments included two rice (‘PB 1’ and ‘PB 1121’) varieties and eight INM practices including N control, recommended dose of N through urea, different combinations of urea with farmyard manure (FYM), green manure (GM), biofertilizer (BF) and vermicompost (VC). The results showed 91.6–92.5 % lower cumulative CH₄ emission in AR compared to FT rice. In aerobic conditions, highest cumulative CH₄ emission (6.9–7.0 kg ha^?1) was recorded with the application of 100 % N by organic sources (FYM+GM+BF+VC). Global warming potential (GWP) was significantly lower in aerobic rice (105.0–107.5 kg CO₂ ha^?1) compared to FT rice (1242.5–1447.5 kg CO₂ ha^?1). Significantly higher amount of water was used in FT rice than aerobic rice by both the rice varieties, and a water saving between 59.5 and 63 % were recorded. Under aerobic conditions, both rice varieties had a water productivity of 8.50–14.69 kg ha^?1, whereas in FT rice, it was 3.81–6.00 kg ha^?1. In FT rice, a quantity of 1529.2–1725.2 mm water and in aerobic rice 929.2–1225.2 mm water was used to produce one kg rice. Thus, there was a saving of 28.4–39.6 % total water in both the rice varieties under AR cultivation.     

Yield potential and water use efficiency of aerobic rice (Oryza sativa L.) in Japan

Intensive rice farming in aerobic soil, referred to herein as aerobic rice, can greatly reduce the water input compared to that of flooded rice cultivation. The objective of this study was to compare the potential productivity of aerobic rice and flooded rice using high-yielding varieties at two locations in Japan in two successive years. In aerobic fields, the total amount of water supplied (irrigation plus rainfall) was 800–1300 mm. The soil water potential at 20-cm depth averaged between −15 and −30 kPa each growing season, but frequently reached −60 kPa. The average yield under aerobic conditions was similar to or even higher than that achieved with flooded conditions (7.9 t ha⁻¹ in 2007 and 9.4 t ha⁻¹ in 2008 for aerobic versus 8.2 t ha⁻¹ for flooded). The average water productivity under aerobic conditions was 0.8–1.0 kg grain m⁻³ water, slightly higher than common values in the literature. The super-high-yielding cultivar Takanari achieved yields greater than 10 t ha⁻¹ with no yield penalty under aerobic conditions in 3 out of 4 experiments. The favorable agronomic characteristic of Takanari was its ample sink capacity (grain number × grain weight). In conclusion, high-productivity rice cultivation in aerobic soil is a promising technology for water conservation. With continued breeding, future aerobic rice varieties will possess large numbers of spikelets and sufficient adaptation to aerobic conditions such that they will consistently achieve yields comparable to the potential yield of flooded rice.     

湖北稻茬小麦主茎、分蘖1、分蘖2和分蘖3的成穗率、产量贡献率及主要农艺性状分析

合理的茎蘖组合是提升小麦绿色高效生产的重要因素。为了解湖北稻茬小麦主要茎蘖对产量及主要农艺性状的影响,以大穗型小麦品种川麦104和多穗型小麦品种扬麦15为材料,于2016-2018年在湖北十堰和武汉两地稻茬麦大田条件下,设置低(1.35×106~1.65×106株·hm^-2)、中(2.85×106~3.15×106株·hm^-2)、高(4.35×106~4.65×106株·hm^-2)三种种植密度,分析了主茎(S)、分蘖1(T1)、分蘖2(T2)和分蘖3(T3)(按出现先后顺序)的成穗率、产量贡献率及相关农艺性状的表现。结果表明:(1)湖北稻茬小麦成穗茎蘖农艺性状表现值偏低,除穗长和茎高受品种的影响最大外,其他被测性状受影响程度表现为蘖位>种植密度>品种;(2)在主茎均能成穗的情况下,分蘖成穗率随蘖位和种植密度的升高而降低,大穗型品种川麦104的降幅大于多穗型品种扬麦15;(3)主茎产量贡献率随种植密度的升高而升高(35.12%~54.50%),分蘖1产量贡献率稳定在23.25%~25.50%,分蘖2和分蘖3的产量贡献率随种植密度升高而降低,分别为14.59%~23.22%和5.42%~16.77%;(4)主茎的穗粒数(35.94~44.13粒)和穗粒重(1.44~1.93 g)显著高于其分蘖,茎高、茎蘖收获指数和穗茎节长只在川麦104中、高种植密度下的分蘖3与其他茎蘖差异显著;穗长、可孕小穗数和不孕小穗数有随蘖位和种植密度升高而变劣的趋势。聚类分析得出:湖北稻茬小麦绿色高效生产模式,以主茎成穗为主体,低种植密度下增加分蘖1和分蘖2,争取分蘖3成穗为辅;中种植密度下争取分蘖1+分蘖2成穗为辅;而高种植密度下争取分蘖1成穗为辅。     

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.     

Impact of water management on yield and water productivity with system of rice intensification (SRI) and conventional transplanting system in rice

The system of rice intensification (SRI) reportedly enhances yield with less water requirement. This claim was investigated to determine the effects of alternative cultivation methods and water regimes on crop growth and physiological performance. Treatment combinations compared SRI with the conventional transplanting system (CTS) using standard practices, evaluating both along a continuum from continuous flooding to water applications at 1, 3, 5, or 7 days after disappearance of ponded water (DAD), subjecting plants to differing degrees of water stress while reducing total water expenditure. SRI methods gave significant changes in plants’ phenotype in terms of root growth and tillering, with improved xylem exudation and photosynthetic rates during the grain-filling stage compared to CTS. This resulted in significant increases in panicle length, more grains and more filled grains panicle^?1, greater 1,000-grain weight, and higher grain yield under SRI management. Overall, averaged across the five water regimes evaluated, SRI practice produced 49 % higher grain yield with 14 % less water than under CTS; under SRI, water productivity increased by 73 %, from 3.3 to 5.7 kg ha-mm^?1. The highest CTS grain yield and water productivity were with the 1-DAD treatment (4.35 t ha^?1 and 3.73 kg ha-mm^?1); SRI grain yield and water productivity were the greatest at 3-DAD (6.35 t ha^?1 and 6.47 kg ha-mm^?1).     

Enhancing the performance of transplanted coarse rice by seed priming

Raising the rice seedlings in the nursery and its transplantation into the flooded fields is principal method of rice cultivation in the world. Traditional nursery raising method in Pakistan is tedious and produces week seedlings, which reduces the final yield due to high mortality. The potential of seed priming to improve the nursery seedlings and thus the transplanted rice was evaluated in the present study. Seed priming tools employed during the investigation included traditional soaking (pre-germination), hydropriming for 48 h, osmohardening (KCl or CaCl₂) (ψs-1.25 MPa) for 24 h (1 cycle), ascorbate priming (with 10 ppm ascorbate) for 48 h or seed hardening for 24 h. Priming improved nursery seedling vigor and resulted in improved growth, yield and quality of transplanted rice. Osmohardening (KCl) consequently resulted in the best performance, followed by osmohardening (CaCl₂)_, hardening and ascorbate priming. Osmohardening (KCl) produced 4.28 t ha⁻¹ (vs. 3.51 t ha⁻¹ from untreated control) kernel yield, 10.27 t ha⁻¹ (vs. 9.34 t ha⁻¹ from untreated control) straw yield and 29.41% (vs. 27.31% from untreated control) harvest index. The improved yield was attributed to increase in number of fertile tillers.