Improving nitrogen and phosphorus use efficiencies through inclusion of forage cowpea in the rice–wheat systems in the Indo-Gangetic Plains of India

In high productivity zones of Indo-Gangetic Plains in south Asia, the rice–wheat system is stressed due to production fatigue as evidenced by declining soil organic matter content, low efficiency of fertilizer use and diminishing rates of factor productivity. We, therefore, conducted field experiments at Modipuram, India, to conserve soil organic carbon, improve N and P use efficiency, and increase yields of rice–wheat system through inclusion of forage cowpea during the summer before cultivating the rice–wheat system. Cowpea forage harvested at 50 days removed greater amounts of N and P through aboveground biomass than those recycled through belowground roots and nodules. The NO₃-N in soil profile below 45 cm depth after wheat harvest was greater under fallow during summer than under cowpea, suggesting that cowpea minimized NO₃-N leaching beyond 45 cm depth. Similarly, in the treatments receiving both 120 kg N and 26 kg P ha⁻¹, NO₃-N in soil below 45 cm depth was lower compared to those receiving N or P alone. After three crop cycles, soil OC content in 0–15 and 15–30 cm depths was greater compared to initial OC in plots having cowpea. P applied at 26 kg ha⁻¹ increased available P content over initial P content, and also over P content of soil under no P treatments. The available P content was, however, invariably low under summer cowpea plots as compared to that under no cowpea ones. With continuous rice–wheat cropping, the bulk density (BD) of soil increased over the initial BD at different profile-depths, more so at 30–45 cm depth in no cowpea plots, but inclusion of summer cowpea helped decreasing the BD in the surface (0–15 cm) and sub-surface (15–30 and 30–45 cm) soil layers. Summer cowpea grown on residual fertility after wheat harvest did not influence rice yield, but increased wheat grain yield (P<0.05 during the terminal year), when both the crops received fertilizer N and P at recommended rates. Skipping of N or P or both, however, resulted in consistently low yield of these crops under summer cowpea treatments than those under no cowpea treatments, although the differences were not necessarily significant every year. The use efficiency of applied N and P fertilizers in rice and wheat, measured as agronomic efficiency and apparent recovery, was increased with the use of fertilizer N and P at recommended rates, and also with inclusion of summer cowpea.     

Long-term effects of inorganic and organic fertilizer sources on yield and nutrient accumulation of lowland rice

Deceleration in rice (Oryza sativa L.) yield over time under fixed management conditions is a concern for countries like Bangladesh, where rice is the primary source of calories for the human population. Field experiments were conducted from 1990 to 1999 on a Chhiata clay loam soil (Hyperthermic Vertic Endoaquept) in Bangladesh, to determine the effect of different doses of chemical fertilizers alone or in combination with cow dung (CD) and rice husk ash (ash) on yield of lowland rice. Two rice crops—dry season rice (December–May) and wet season rice (July–November) were grown in each year. Six treatments—absolute control (T₁), one-third of recommended fertilizer doses (T₂), two-thirds of recommended fertilizer doses (T₃), full doses of recommended fertilizers (T₄), T₂+5 t CD and 2.5 t ash ha⁻¹ (T₅) and T₃+5 t CD and 2.5 t ash ha⁻¹ (T₆) were compared. The CD and ash were applied on dry season rice only. The 10-year mean grain yield of rice with T₁ was 5.33 t ha⁻¹ per year, while the yield with T₂ was 6.86 t ha⁻¹ per year. Increased fertilizer doses with T₃ increased the grain yield to 8.07 t ha⁻¹ per year, while the application of recommended chemical fertilizer doses (T₄) gave 8.87 t ha⁻¹ per year. The application of CD and ash (T₅ and T₆) increased rice yield by about 1 t ha⁻¹ per year over that obtained with chemical fertilizer alone (T₂ and T₃, respectively). Over 10 years, the grain yield trend with the control plots was negative, but not significantly, both in the dry and wet seasons. Under T₃ through T₆, the yield trend was significantly positive in the dry season, but no significant trend was observed in the wet season. The treatments, which showed positive yield trend, also showed positive total P uptake trend. Positive yield trends were attributed to the increasing P supplying power of the soil.     

浙江金华地区水稻土养分供应能力研究

 自1997年早稻开始，在浙江省金华市农业科学研究所试验区稻田设立了监测水稻土生产力及肥力变化的长期肥料定位试验，并在试验区周围10 km范围内选择了21户农民的稻田进行相应的监测试验。试验区内农户间稻田土壤的养分供应能力相差很大，氮供应能力变化于49~116 kg/hm2，磷供应能力变化于13~32 kg/hm2，钾供应能力变化于68~183 kg/hm2。农民常规施肥区的氮肥利用效率很低，氮表观回收率的平均值为14%~26%，氮肥农业效率平均值为4.6~8.2，且农户之间、早晚稻之间均存在较大差异。肥料定位试验结果表明，在连续种植水稻条件下，缺肥区土壤相应的有效养分消耗很快。与NPK全肥区比较，NP区从第2季水稻起，NK区从第3季水稻起，即开始出现减产。针对当地农民现行养分管理的实际情况，就水稻系统发展适地养分综合管理新技术进行了讨论。     

稻田年内水旱轮作的后效应研究

 在麦-稻-稻和麦-玉米-稻两种种植方式6年定位试验的基础上,对稻田年内水旱轮作的后效应进行了研究。结果表明：年内水旱轮作能显著地提高后作晚稻和大麦产量,但后效持续时间不长,到第三季后作物早稻增产已不明显。生产上两种种植方式以隔年轮换为好。增产的主要原因是年内水旱轮作改善土壤通透性,能增加土壤有效氮、磷、钾含量和提高根系活力,促进了作物生长和养分吸收,从而增加晚稻有效穗、结实率和实粒数,增加大麦有效穗和千粒重。试验也表明,增施肥料会降低轮作效果。     

长期绿肥还田对江南稻田系统生产力及抗逆性的影响

 依据江南丘陵地区双季稻田28年（1981-2008年）长期绿肥还田的田间定位试验和4年的养分耗竭盆栽试验,分析比较了长期不同量绿肥还田对稻田系统生产力和抗逆性的综合影响。结果表明,常量绿肥还田和高量绿肥还田处理下,早稻、晚稻和历年的全年平均籽粒产量和生物学产量及其变异系数与长期单施化肥处理差异不显著,但由于绿肥还田处理施用绿肥替代部分化肥,平均每年的化肥N、P和K投入量比单施化肥处理分别减少90.0、9.9和72.0 kg/hm2。绿肥处理的双季稻全年产量呈上升趋势,而长期化肥处理则呈下降趋势,且前者的全年产量可持续性产量指数均略高于后者,常量绿肥还田下稻田系统的耐瘠能力也显著高于长期单施化肥处理。不同量绿肥还田下稻田系统生产力差异不显著,但耐瘠能力常量还田处理较高。     

Evaluation of Water-Saving Rice-Winter Crop Rotation System in a Suburb of Tokyo

Abstract

Water-saving rice-winter crop rotation systems were repeated for 4 cycles from 2000 to 2004 in an urban area, Nishitokyo, Japan, to assess the effects of water-saving (i.e. non-flooded vs. flooded) on grain yield of rice (Oryza sativa L.) and chemical constituents of percolating water. The effects of pre-rice winter cropping compared with fallow on rice yield were also examined. The pre-cultivated crops were wheat (Triticum aestivum L.), italian ryegrass (Lolium multiflorum Lam.) or spinach (Spinacea oleracea L.) with their above-ground parts removed, chinese milk vetch (Astragalus sinicus L.) or rapeseed (Brassica napus L.) with their above-ground parts incorporated before rice transplanting. Neither winter cropping effects nor its interaction with water-saving were significant for rice yield, although the yield after rapeseed incorporation tended to be 9 % higher than that after fallow. In 2001, 2003 and 2004, when more than 70% of irrigation water was saved in the non-flooded trial, average yield in non-flooded trial was 58 % of flooded trial, but water productivity increased (from 0.10 to 0.16 kg m^-3). Among the 3 years, yield in non-flooded trial was highest in 2004 when the amounts of irrigation and total water supply was larger, the frequency of dry spells was the lowest, and 2 seedlings were transplanted per hill. The nitrate and nitrite concentrations in the percolating water were far below the environmental standard values by WHO. The study showed that incorporation of winter crops had no negative effects on water-saving rice production at least for the first 4 years, and that under extreme water-saving, irrigation and planting methods could minimize yield reduction.     

Morphological analysis on comparison of organic and chemical fertilizers on grain quality of rice at different planting densities

ABSTRACT

Effects of organic (Italian ryegrass and Bokashi) and chemical fertilizer on growth, yield, and grain quality of rice (Oryza sativa L.) were compared under different planting densities in 2013/2014 and 2014/2015. Italian ryegrass was incorporated into the soil as green manure. Bokashi (a mixture of organic materials) was applied as basal dressing. To measure yield and its components, 30 hills were chosen for each treatment. Rice grains were harvested from each treatment to assess the grain quality and to evaluate accumulation structures using a scanning electron microscope. Bokashi treatment increased panicle number per hill, ripened grain percentage, panicle number per m², and grain yield compared to no fertilizer treatment at normal planting density. Chemical fertilizer treatment increased plant length at high planting density. Italian ryegrass and Bokashi treatments promoted the taste point (taste score as reference) by reduction of amylose and protein contents at normal planting density in contrast to chemical fertilizer. 1000-grain weight, panicle number per m², and grain yield were higher at high planting density than at normal planting density. However, high planting density decreased panicle number per hill and spikelet number per panicle. It also enhanced the amylose content of rice grain. Scanning electron microscopic observation revealed that chemical fertilizer treatment marked up protein bodies and their traces on amyloplasts. However, Bokashi treatment produced large amyloplasts, which included many starch granules. These results show that Italian ryegrass and Bokashi can offset reductions of chemical fertilizer and can lead to sufficient starch accumulation structures in rice grains.     

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.     

Changes in Grain Yield of Rice and Emission of Greenhouse Gases from Paddy Fields after Application of Organic Fertilizers Made from Maize Straw

A field experiment was conducted at the farm of Yangzhou University, Yangzhou, China, to study the effects of organic fertilizers made from maize straw on rice grain yield and the emission of greenhouse gases. Four organic fertilizer treatments were as follows： maize straw （MS）, compost made from maize straw （MC）, methane-generating maize residue （MR）, and black carbon made from maize straw （BC）. These organic fertilizers were applied separately to paddy fields before rice transplanting. No organic fertilizer was applied to the control （CK）. The effects of each organic fertilizer on rice grain yield and emission of greenhouse gases were investigated under two conditions, namely, no nitrogen （N） application （ON） and site-specific N management （SSNM）. Rice grain yields were significantly higher in the MS, MC and MR treatments than those in CK under either ON or SSNM. The MS treatment resulted in the highest grain yield and agronomic N use efficiency. However, no significant difference was observed for these parameters between the BC treatment and CK. The changes in the emissions of methane （CH4） carbon dioxide （CO2）, or nitrous oxide （N20） from the fields were similar among all organic fertilizer treatments during the entire rice growing season. The application of each organic fertilizer significantly increased the emission of each greenhouse gas （except N20 emission in the BC treatment） and global warming potential （GWP）. Emissions of all the greenhouse gases and GWP increased under the same organic fertilizer treatment in the presence of N fertilizer, whereas GWP per unit grain yield decreased. The results indicate that the application of organic fertilizer （MS, MC or MR） could increase grain yield, but also could enhance the emissions of greenhouse gases from paddy fields. High grain yield and environmental efficiency could be achieved by applying SSNM with MR.     

Effects of a Microbial Inoculant and Organic Fertilizers on the Growth,Photosynthesis and Yield of Sweet Corn

Summary

A microbial inoculant known as Effective Microorganisms or EM is a mixed culture of naturally-occurring, beneficial microorganisms (predominantly lactic acid bacteria, yeast, actinomycetes, photosynthetic bacteria and certain fungi) that has been used with considerable success to improve soil quality and the growth and yield of crops, particularly in nature farming and organic farming systems. Despite this success, the exact mechanisms of how this EM elicits such beneficial effects is largely unknown. Consequently, a study was conducted to determine the effects of EM and organic fertilizer on the growth, photosynthesis, and yield of sweet corn (Zea mays L.) under glasshouse conditions, compared with chemical fertilizer. An organic fertilizer consisting of a mixture of oilseed mill sludge, rice husk and bran, and fish processing waste, was inoculated and fermented with EM as the microbial inoculant. The organic fertilizer and chemical fertilizer were then applied to respective pots to compare the growth, yield and physiological response of sweet corn plants. EM applied with the organic fertilizer was shown to promote root growth and activity, and to enhance photosynthetic efficiency and capacity, which resulted in increased grain yield. This was attributed largely to a higher level of nutrient availability facilitated by EM application over time. Interestingly, during the early stage of the experiment, the growth and dry matter yield of plants that received organic fertilizer were actually lower than those treated with chemical fertilizer that provided higher initial levels of macronutrients. However, during the intermediate and late growth stages, EM increased the nutrient availability of the organic fertilizer to a higher level, than the chemical fertilizer. Consequently, even though there was an early lower growth rate for plants that received EM-fermented organic fertilizer compared with chemical fertilizer, the final biomass and grain yield from organic fertilizer was equal to or higher than from chemical fertilizer.     

Land Equivalent Ratio of Groundnut-Fingermillet Intercrops as Affected by Plant Combination Ratio,and Nitrogen and Water Availability

Abstract

Field experiments were conducted to characterize intercropping advantages in groundnut-fingermillet intercrop in relation to crop combination ratios, soil moisture and nitrogen (N) availability. Three intercrops in 1 : 2, 1 : 1 and 2 : 1 alternating rows of groundnut and fingermillet were examined for their growth and yield in comparison with their respective sole crops in 1996. The effect of well watered (W) and water stressed (D) conditions on the intercropping advantage was also examined for 1 : 1 intercrops in 1995 and 1996. Fertilizer N was applied at the rate of 20 kg ha^?1 in 1995 and 50 kg ha^?1 in 1996. The total above-ground biomass (DM) and its land equivalent ratio (LER) were highest in the 1 : 1 combination ratio. The DM production of intercropped fingermillet was higher in 1996 with higher N than in 1995 with low N application, while those of groundnut were similar in both years. The intercropped groundnut exhibited significantly higher DM production after the fingermillet harvest. The LERs in grain yield were higher in 1996 (1.43 under W and 1.45 under D), than in 1995 (0.87 under W and 1.22 under D). Also, LERs were consistently higher under D than W conditions. Water stress severely reduced the leaf area index (LAI) of fingermillet at a low N, especially in the later stages, whereas higher N alleviated the water stress effect. A close linear relationship was observed between LAI and leaf area (LA) per unit leaf N both for groundnut and fingermillet, with intercrops producing larger LA per unit leaf N than sole crops. Intercropping maintained higher ability in leaf net photosynthesis and transpiration of groundnut up to later stages, and significantly reduced water evaporation from the soil surface under the canopy than sole cropping of fingermillet. These results suggest that three processes associated with the intercropping yield advantages in the groundnut-fingermillet intercrop; 1) higher leaf photosynthesis and vigorous growth of groundnut after the fingermillet harvest, 2) higher LA production per unit N and 3) efficient water use. In conclusion, interspecific shading was considered to be the key mechanism associated with these processes, leading to the intercropping advantages. The degree of the interspecific shade and its effect on growth and yield depended on the available soil N and water.     

缓/控释肥对双季稻产量和氮素利用率的影响

为明确缓/控释肥(slow/controlled-release fertilizer,CRF)在水稻上的应用效果,连续2年在南方双季稻区第四纪红壤发育的水稻土上进行双季稻大田试验,比较了不施氮肥(CK)、推荐分3次施肥(OF)、一次性基施缓/控释肥(100CRF)和一次性基施80%缓/控释肥(80CRF)条件下,双季稻的产量形成、氮素吸收和利用的差异。结果表明,2年4季产量平均表现为80CRF100CRFOFCK,其中80CRF、100CRF和OF分别比CK增产25.32%、23.93%和22.54%(P0.05),而各施氮处理间无显著差异;2年籽粒平均吸氮量中,早稻100CRF、80CRF处理均显著高于OF处理(P0.05),晚稻100CRF处理显著高于OF处理(P0.05),但80CRF处理与OF无显著差异,秸秆吸氮量与籽粒一致。100CRF、80CRF处理下氮肥吸收利用率均显著高于OF处理(P0.05);氮肥农学利用率、氮肥偏生产力以80CRF最高,显著高于100CRF和OF处理(P0.05);2012年晚季80CRF的氮肥生理利用率、土壤氮素依存率最高,显著高于100CRF处理(P0.05),2013年早晚稻均以OF处理最高,显著高于100CRF处理(P0.05);2年定位试验中的80CRF处理与OF处理氮素生理利用率无显著差异。因此,一次性施用缓/控释肥产量水平与推荐分次施肥水平相当,但施用缓/控释肥能显著提高水稻氮素吸收量和含量。全量施缓/控释肥虽能提高早晚稻氮肥吸收利用率,但氮素生理利用率降低;在推荐施肥的基础上减量20%施用缓/控释肥的早晚稻氮肥吸收利用率、农艺利用率、偏生产力均显著提高,氮肥生理利用率与推荐施肥无差异;即在稳产的基础上,提高了氮素的利用效果,是值得推荐的施肥方式。     

The phosphorus requirements of five consecutive potato crops on an Andept in Rwanda

Farmers in Rwanda do not apply P fertilizer on their crops. Bray and Kurtz #1 extractable P levels are generally less than 2 ppm on these soils. Therefore, a long-term experiment was established to determine the yield response of potatoes to P fertilizer. A maximum accumulated yield of 130 t/ha in 5 crops was obtained with 902 kg/ha of P. The no P treatments produced 72% of the average maximum yield. The external P requirements, determined with P sorption isotherms, averaged 0.04 μg/ml if equilibrated at 15 C and 0.02 μg/ml if equilibrated at 25 C for the 5 crops. The residual efficiency of the applied P fertilizer was less than 20%, suggesting that large applications of P are not advisable on Andepts, which have amorphous materials because the applied P is not available for subsequent cropping seasons.     

Water supply from pearl millet by hydraulic lift can mitigate drought stress and improve productivity of rice by the close mixed planting

The authors have proposed the close mixed planting technique using mixed seedlings of two different crop species that results in close tangling of their root systems. Especially, the combination of drought-adaptive upland crops (e.g. pearl millet or sorghum) and flood-adaptive lowland crop of rice would be beneficial to overcome the drought and flood conditions and to reduce the risks of crop failure. In our previous studies, we found that upland crop yield losses by flood stress was mitigated by mix-cropped rice, owing to the oxygen gas released from the rice roots into the aqueous rhizosphere. In the present study, we conducted two experiments to assess whether mixed cropping a drought-resistant cereal, pearl millet, would improve the performance of co-growing drought-susceptible crop, rice under drought conditions. In the field experiment, some grains were obtained from the rice plants mix-cropped with pearl millet under drought condition. However, no rice matured in the single cropping system. In the model experiment using deuterium analysis, it was confirmed that water absorbed by pearl millet roots from deep soil layer was utilized by rice, suggesting that mix-cropped rice could withstand drought stress and complete grain filling using water released into the upper soil layer by hydraulic lift.     

水分胁迫和供氮形态耦合作用下分蘖期水稻的光合速率、水分与氮素利用

采用室内营养液培养及PEG模拟水分胁迫的方法,在3种供氮形态\[NH4+、NO3-、NH4+/NO3-(质量比)为50∶50\]下,主要研究分蘖期水稻在非水分胁迫及水分胁迫条件下的氮素利用效率及对不同形态氮素的消耗。在非水分胁迫条件下,分蘖期水稻在NH4+/NO3-为50∶50时生物量增量最大;而在水分胁迫条件下,单一供NH4+ N营养的水稻生物量增量最大。在两种水分条件下,当NH4+/NO3-为50∶50时,分蘖期水稻对营养液中NO3- N的消耗量明显大于NH4+ N;此外,在两种水分条件下,均以单一供NH4+ N营养水稻的光合速率、氮素利用率和水分利用率最高。     

Quantitative effects of cultural practices on growth and yield of forage rice having short panicles

Cultivation of forage rice for whole-crop silage has been increasing in Japan and will be important in Asia. In this study, effects of cultural practices on growth and yield of a forage rice cultivar “Tsukisuzuka” having short panicle 1 allele were analysed quantitatively using linear mixed model. The contribution of basal dressing to dry yield per 1 g/m² nitrogen fertilizer was larger than that of topdressing. In addition, topdressing 30 and 20 days before heading was considered to have the disadvantage of increasing risk of lodging and panicle weight respectively. Effects of weather elements on growth of forage rice were also speculated. In tested fields, high solar radiation at seedling and tillering stage was considered important for the high yield. As the number of continuous cropping cycles increased, growth of forage rice got worse. And application of compost improved growth of forage rice. Elemental analysis of soil and plants revealed that this continuous cropping obstacle was likely to attributed to deficiency of potassium. In addition, potassium deficiency increased panicle weight of a forage rice cultivar having short panicle 1 allele. Therefore, control of potassium nutrition will be useful for both sustaining productivity (sufficient application of potassium) and seed production (restriction of potassium). These findings will be useful for improvement of cultivation method of forage rice.     

湘南丘岗地区水稻轻简施肥技术的效应研究

通过田间小区试验,系统研究了在几种轻简施肥技术条件下双季早、晚稻的生育特性、养分吸收规律、肥料养分的当季利用率、经济性状和产量效应以及土壤速效养分的变化规律。结果表明：在轻简施肥技术条件下,双季稻前期早发不明显,中期成穗率高,后期根旺叶健不早衰;早、晚稻不同生育时期的干物质积累量与养分的吸收量具有相似性;早稻前期氮、磷、钾吸收量最低,绝大部分氮、磷、钾养分是在中、后期吸收的,晚稻前期的氮、磷、钾吸收量明显高于早稻,后期的氮、磷、钾吸收量大多低于早稻,不同处理之间差异不大。各轻简施肥处理均能提高早稻对氮和磷的表观利用率,以“湘珠专用肥”处理效果最好,但不能提高早稻对钾的表观利用率;晚稻轻简施肥处理“湘珠专用肥”也能明显提高水稻对肥料氮和钾的表观利用率。轻简施肥处理的水稻产量明显高于当地习惯施肥处理。     

再生稻肥料管理对不同品种产量和品质的影响

【目的】探明肥料管理、品种及其互作对再生稻头季和再生季产量和品质的影响,为再生稻高产优质育种和栽培提供理论依据。【方法】采用大田试验的方法,以4个华中地区主推的再生稻品种为材料,设置4种肥料管理方法,分别测定水稻的产量和产量构成因素、稻米品质(加工品质和外观品质)、干物质生产及相关农艺性状等。【结果】相比推荐施肥对照(CK),全生育期施用再生稻专用缓释肥(SRF)使两季施肥的次数从5次减少到3次,而且产量在头季和再生季分别达8.86和6.39 t/hm ²,较CK仅降低了6.2%和9.1%。SRF在头季减产主要归因于较低的结实率,而在再生季减产是每穗颖花数和总颖花数共同下降的结果。促芽肥施与不施对再生季产量没有影响。再生稻两季的加工品质和外观品质主要受品种的影响,肥料处理及其与品种的互作影响很小。相比其他3个品种,甬优4949的头季和再生季产量最高,加工品质和外观品质最好。【结论】施用专用缓释肥和省施促芽肥均能够在不大幅损失稻谷产量的同时减少施肥次数促进再生稻轻简化栽培。     

Yield and land-use efficiency of a cassava/cowpea intercropping system grown at different phosphorus rates

Cassava (Manihot esculenta Crantz) is frequently intercropped with cowpea [Vigna unguiculata (L.) Walp subsp. unguiculata] in the tropics. Little is known about the influence of P fertilization practices on the efficiency of land use and yields in cassava/cowpea intercropping systems. Two experiments were conducted on a Typic Dystropept soil with the objective of determining the influence of P application rate on yield and P status of cassava and cowpea grown in sole and intercropping systems, and the influence on land use efficiency. Cassava yields averaged across P rates were reduced 29% from the 28 Mg ha⁻¹ sole crop yield when intercropped with cowpea in 1979–1980. Cowpea yields were reduced by 19–38% from a sole crop yield of 1522 kg ha⁻¹ when intercropped in 1979, and 29–38% from a sole crop yield of 1277 kg ha⁻¹ in 1980. The rate of P application had little influence on cassava yield, except in 1981 when intercropped cassava yields were greater than 40 Mg ha⁻¹. In 1981, increasing the rate of P application from 0 to 44 kg ha⁻¹ resulted in a cassava yield increase from 41 to 47 Mg ha⁻¹. In 1979 and 1980, increasing the rate of P application from 0 to 22 kg ha⁻¹ increased cowpea yield 44 and 92%, respectively, while increasing P rate from 66 to 132 kg ha⁻¹ increased cowpea yield 28 and 18%, respectively. In 1981 and 1982, increasing the rate of P application from 0 to 44 kg ha⁻¹ increased cowpea yield by 1052 kg ha⁻¹. Phosphorus concentration of cassava and cowpea leaf blades increased with increases in rate of P application from 66 to 132 kg ha⁻¹ in 1979 and 1980, and from 0 to 44 kg ha⁻¹ in 1981 and 1982. Intercropping cassava with cowpea resulted in a 30% increase in land-use efficiency when no P was applied, while land-use efficiencies resulting from intercropping were increased by 41–50% with P application rates of 22–132 kg ha⁻¹. Cassava proved to be well-adapted to low-P soils and very competitive even without P application, whereas cowpea required the addition of P for adequate growth and yield. High productivity and a good competitive balance between the two crops were reached with only 22 kg ha⁻¹ of P, showing the great potential of cassava/cowpea intercropping on acid, infertile soils in the tropics.     

不同生育时期施用硅肥对优质食味粳稻产量和品质的影响

探究不同生育时期施用硅肥对优质食味粳稻产量和品质的影响,可为优质食味粳稻合理施硅提供理论基础和技术支撑。以优质食味粳稻品种南粳9108为试验材料,以不施肥（CK1）和常规施肥（CK2）为对照,在常规施肥的基础上分别设置硅肥浸种（T1）、硅肥浸种+苗期喷施硅肥15 kg/hm²（T2）、硅肥浸种+拔节期喷施硅肥15 kg/hm²（T3）、硅肥浸种+抽穗期喷施硅肥15 kg/hm²（T4）、硅肥浸种+苗期20%、拔节期30%、抽穗期50%喷施硅肥15 kg/hm²（T5）、硅肥浸种+苗期1/3、拔节期1/3、抽穗期1/3喷施硅肥45 kg/hm²（T6）处理,比较不同施硅方式对水稻产量和品质的影响。结果表明,T6处理产量最高,其次是T5、T4、T3处理,T1和T2处理产量较CK2增幅较小;不同硅肥处理单位面积穗数、每穗颖花数、千粒重和结实率较不施硅处理均有不同程度提高。施硅对产量构成因素的影响大小依次为每穗颖花数>单位面积穗数>千粒重>结实率,T3、T5和T6处理的单位面积穗数和每穗颖花数增幅较大。与CK2相比,T3、T4、T5和T6处理增加了水稻库容量、源强度及源库比,提高了糙米率、精米率和整精米率,同时降低了垩白粒率、垩白度及蛋白质含量。T6处理稻米的峰值黏度、热浆黏度、崩解值、最终黏度较CK2显著提高,而其他处理对稻米淀粉黏滞谱特性的影响不显著。主成分分析结果表明,不同硅肥处理对水稻产量和品质影响的大小依次为T6>T5>T4>T3>T2>T1。综合考虑硅肥投入、水稻产量及品质,在常规施肥加硅肥浸种基础上,优质食味粳稻推荐硅肥施用方式为：喷施量15 kg/hm²,苗期占20%、拔节期占30%、抽穗期占50%。