喷灌施肥灌溉均匀性对土壤硝态氮空间分布影响的田间试验研究

在2002～2003年冬小麦生育期内进行了喷灌施肥条件下均匀系数对土壤水氮时空分布及淋失影响的田间试验。试验中,喷灌均匀系数设置低、中、高三个处理,灌溉季节内的平均喷灌均匀系数分别为72%、79%和84%,施肥灌溉均匀系数分别为71%、78%和85%。对70和90 cm深度处的土壤水势进行了监测以评估均匀系数对水氮淋失的影响,结果表明,在所研究的喷灌均匀系数范围内深层渗漏量很小。试验结果还指出,土壤硝态氮随时间和空间表现出很强的变化特征,均匀系数变化范围为23%～97%,变差系数的变化范围为0.04～1.00;灌溉季节内土壤硝态氮分布的均匀性主要取决于初始硝态氮分布的均匀程度,而喷灌均匀系数对土壤氮素的空间分布无明显影响。     

基于称重式蒸渗仪的喷灌条件下冬小麦和糯玉米作物系数估算方法

利用位于北京的称重式蒸渗仪,对喷灌条件下的冬小麦和糯玉米需水规律进行了测定,进而计算了两种作物的作物系数。结果表明,冬小麦和糯玉米的作物系数与播种后天数之间的关系均可以用四次多项式来表征。根据FAO-56推荐的作物系数计算方法,计算了两种作物的分段单值作物系数和双作物系数,发现华北平原喷灌条件下冬小麦和糯玉米的作物系数在生育期内的变化可以用FAO-56推荐的模式来描述,但实测值一般大于FAO-56的建议值。为了能利用FAO-56推荐的模式较好地描述喷灌作物系数变化规律,依据实测资料对FAO-56建议的单值作物系数和基础作物系数进行调整后,模拟了两种作物需水量的变化,模拟的作物阶段需水量与实测值吻合良好。     

Bt伴孢晶体毒素对不同时期中华卵索线虫的毒力

采用不同浓度的10株Bt伴孢晶体蛋白分别作用于中华卵索线虫受精卵及各期幼虫,探讨该类Bt蛋白对多种农林害虫天敌中华卵索线虫的安全性。结果表明:S1-1、S1-4、S3-2、S3-3、S7-1、S7-6和S8-1等7个菌株同时表达cry1Ac和cry5基因,S1-8、S2-1和HD-1等3个菌株只表达cry1Ac基因。含Cry5蛋白的菌株对线虫卵表现出一定的杀灭毒性,其中S1-4菌株的毒力最强,LD50作用24、48和72h时分别为0.1503、0.1313和0.0182μg/mL。而Bt伴孢晶体蛋白对感染期幼线虫和寄生后期幼线虫无明显致死效应;经Bt处理的感染期幼线虫对棉铃虫的感染率及平均感染强度与对照组无显著性差异(P>0.05),寄生后期幼线虫能正常蜕皮和交配产卵。将含上述浓度Bt蛋白的棉花叶片喂食已感染线虫的棉铃虫,线虫能够正常发育并从宿主体内脱出。     

Can carbon isotope discrimination and ash content predict grain yield and water use efficiency in wheat?

Drought is the main factor affecting crop grain yield. Increasing grain yield under drought and crop water use efficiency (WUE) is essential for enhancing world crop production and food availability. The objective of this study, carried out in India on 20 durum wheat cultivars, under three water regimes (full irrigation, limited irrigation and residual soil moisture) and during two seasons, was to investigate the potential use of plant traits (particularly carbon isotope discrimination, Δ, and ash content, m_a) to predict grain yield and WUE in wheat. WUE components were estimated using a soil water balance model (Budget) allowing comparison of environments in data scarce situations. A highly significant correlation was noted between grain yield and grain Δ across water regimes. However, the associations between grain yield, Δ and m_a were found to depend highly on the water regime and environmental conditions. The association between grain yield and grain Δ was significant under full irrigation in season 1 and under residual soil moisture in season 2. Significant positive correlations were noted in both seasons between grain yield and leaf Δ under residual soil moisture and between grain yield and leaf ash content at anthesis under limited irrigation. A significant correlation was found across environments between grain and leaf Δ and T, the quantity of water transpired during the growth cycle, as estimated by the soil water balance model. T also significantly correlated to grain and leaf m_a. Variation in WUE across environments was driven more by runoff, drainage and soil evaporation than by harvest index and transpiration. The associations between WUE and transpiration, runoff and Δ were negative but not significant. WUE was significantly correlated with leaf and grain m_a at maturity. The study indicates that Δ and m_a can be used as indirect selection criteria for grain yield and suggests that m_a is a good predictor of transpiration, grain yield and WUE across environments. The use of mechanistic models that allows differentiating between cultivars should permit in a next future to analyze the relationships between WUE, Δ and m_a across cultivars and evaluate the possibility to use these traits as predictors of WUE in wheat breeding programs.     

Mapping agricultural responses to water supply shocks in large irrigation systems, southern India

Irrigated agriculture experienced a water supply shock during a drought in southern India in 2002-2003. In this paper, hotspots of agricultural change were mapped and put in the context of hydrology and water management. Time series of MODIS imagery taken every eight days before (2001-2002) and during (2002-2003) the supply shock were combined with agricultural census data to document changes in cropping patterns in four large irrigation projects in the downstream sections of the Krishna and Godavari River basins (total command area 18,287 km²). The area cropped in rice in the four irrigated command areas decreased by 32% during the drought year, and rice production in the two districts that experienced the largest flow reductions fell below production levels of 1980. The irrigation project that showed the largest change in double cropped area (−90%) was upstream of the Krishna Delta. In the Krishna Delta, large areas changed from rice-rice to rice-gram double cropping. Historical water management contributed to the vulnerability of rice production to drought: the main reservoir in the system was drained to dead storage levels by the end of each growing season over 1968-2000, with little carryover storage. The land cover change maps suggested that the lower Krishna Basin has experienced a “hard landing” during basin closure, and revised management strategies that account for the new flow regime will be required to maintain agricultural production during droughts.     

Two Metal Ions Improve Brightness in Wheat-Dough Products and Affect Aqueous Dispersion of Gluten

Zinc and aluminum ions at 0.05% of wheat flour, dry basis (7.4 and 18.5 mmol/100 g, respectively), improved the brightness of raw and dried spaghetti and salt and alkaline noodles. They also retarded bacteria and yeast and mold growth in salt noodles held at 25°C for two days as determined by total plate counts. Neither metal ion caused a change in noodle cooking quality, but they imparted a slight aftertaste in cooked noodles. Wheat flour dough mixed with 0.05% zinc or 0.025% aluminum ion (fwb), when kneaded in aqueous 0.1% calcium chloride, gave gluten with increased brightness. Zinc and aluminum ions appear to complex with enzymic browning chromophores in wheat dough and gluten and change their spectral properties. Zinc and aluminum ions affected the dispersion of gluten in water at pH ~5.0 and facilitated its spray-drying, but they were not detrimental to baking quality. Citric and tartaric acids at 5 mmol/100 g of gluten (db) gave wet gluten with pH ~4.5, which improved its brightness and water dispersibility.     

Sulfur mineralization in two soils amended with organic manures,crop residues,and green manures

The mineralization of sulfur (S) was investigated in a Vertisol and an Inceptisol amended with organic manures, green manures, and crop residues. Field‐moist soils amended with 10 g kg^—1 of organic materials were mixed with glass beads, placed in pyrex leaching tubes, leached with 0.01 M CaCl₂ to remove the mineral S and incubated at 30 °C. The leachates were collected every fortnight for 16 weeks and analyzed for SO₄‐S. The amount of S mineralized in control and in manure‐amended soils was highest in the first week and decreased steadily thereafter. The total S mineralized in amended soils varied considerably depending on the type of organic materials incorporated and soil used. The cumulative amounts of S mineralized in amended soils ranged from 6.98 mg S (kg soil)^—1 in Inceptisol amended with wheat straw to 34.38 mg S (kg soil)^—1 in Vertisol amended with farmyard manure (FYM). Expressed as a percentage of the S added to soils, the S mineralized was higher in FYM treated soils (63.5 to 67.3 %) as compared to poultry manure amended soils (60.5 to 62.3 %). Similarly the percentage of S mineralization from subabul (Leucaena leucocephala) loppings was higher (53.6 to 55.5 %) than that from gliricidia (Gliricidia sepium) loppings (50.3 to 51.1 %). Regression analysis clearly indicated the dependence of S mineralization on the C : S ratio of the organic materials added to soil. The addition of organic amendments resulted in net immobilization of S when the C : S ratio was above 290:1 in Vertisol and 349:1 in Inceptisol. The mineralizable S pool (S_o) and first‐order rate constant (k) varied considerably among the different types of organic materials added and soil. The S_o values of FYM treated soils were higher than in subabul, gliricidia, and poultry manure treated soils.     

Preparation of Porous <Emphasis Type="Italic">m</Emphasis>-aramid/cellulose Blend Membranes with High Moisture and Air Permeability by an Enzymatic Degradation Method

Enzyme degradation method was adopted to prepare porous m-aramid/cellulose blend membranes with high air permeability, water absorbency and moisture permeability. This facile preparation process started by casting a blend membrane from a DMAc/LiCl solution containing m-aramid and cellulose. An enzyme was then used to degrade the cellulose in the blend membrane, resulting in porous structures. Five enzymes including cellulase, chitosanase, papain, lipase, and glucose oxidase, were evaluated and cellulase was found to be optimal. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to characterize the miscibility and the morphology of the m-aramid/cellulose blend membranes before and after degradation, respectively. The thermal stability of the blend membranes were characterized by thermogravimetric analysis (TGA). The properties including air permeability, water absorbency and moisture permeability of the m-aramid/cellulose blend membranes greatly improved after degradation as compared to those of the pure m-aramid. This paper provided a new approach to preparing novel textile materials with high comfortability.     

增氧对水培棉花生长的影响研究

通过水培试验研究增氧对棉花生长的影响;试验设计3种增氧方式,分别为持续性增氧(Physical continuous oxygen,PCO)、间歇性增氧(Physical oxygen,PO),化学增氧(Chemical oxygen,CO),种棉花不增氧CK,不种棉花不增氧CK0;研究结果表明,不同增氧方式对营养液中溶解氧浓度都有不同程度的提高,表现为PCOPOCOCK;PCO处理对根体积、根系总吸收面积、根活性面积、根系生物量、株高、地上部生物量、氮和钾的吸收量的促进作用均达到显著水平,分别比CK增加了194.62%、261.89%、301.73%、57.15%、22.76%、38.03%、35.27%、84.78%;间歇性增氧PO处理对根系生物量、株高、地上部分生物量的促进作用显著,分别比CK高30.83%、15.65%、21.19%。通过以上结果表明,棉花对氧的需求敏感,不同增氧方式均能在一定程度上促进棉花生长,其中持续性增氧效果尤为突出,特别是对棉花生物量的积累,说明增氧可以提升棉花生长潜力。