Residue management for reducing evaporation in relation to soil type and evaporativity1

Abstract. Usual residue-management options are to remove the residue, use it as mulch with or without undercutting or to incorporate it into the soil. While the role of surface mulch in evaporation has been widely studied, the information on the effect on evaporation of mulch with undercutting or residue incorporated into soil, particularly in relation to soil type and evaporativity (E_o) is lacking. We studied the effect of wheat straw used in various ways on the course of evaporation loss from soil columns with three soils at Ludhiana, India and one soil at Bushland, Texas, USA, under two E_o's Energy-limited evaporation rates under mulch (E_om) followed the soil-specific relation E_om/E_o= a e^(bRes+cEo), where Res is residue rate t/ha and a, b and c are constants; E_o, is expressed in mm/d. In an effort to model the total evaporation (CE) during the energy-limited stage ‘U’ was obtained from appropriate CE versus time curves and (CE-U) was regressed over (t - ti)^0.5 to obtain the slope ‘α’ (Ritchie 1972) for the soil-limited evaporation stage. The observed ‘U’ was independent of mulch rate and E_o but was strongly affected by soil type, Values of ‘α’ decreased with increase in mulch rate and decrease in E_o and coarseness of soil. The otherwise short lived benefit of evaporation reduction with mulch per se, which peaked after a few days was maintained when residue was mixed with soil at the stage when evaporation reduction reached a maximum; this benefit continued for several weeks. Cumulative evaporation values computed from ‘U’ and ‘α’ agreed closely with the observed values under straw mulch for loamy sand and clay loam soils and for ‘undercut’ and ‘residue mixed’ treatments on all soils regardless of E_o, and for all situations under small E_o. However, for sandy loam and silt loam soils under E_o of 10 mm/d, the modified square root of the time function of Jalota et al. (1988) gave a better fit.     

稻麦两熟制下秸秆还田模式的产量和经济效益分析

明确不同秸秆还田模式对小麦、水稻产量和经济效益的影响,对推广秸秆还田具有重要意义。利用稻麦复种长期田间定位试验2012-2018年的数据,分析了秸秆不还田（S0）、麦秸还田（WS）、稻秸还田（RS）和稻麦秸均还田（WRS）4种秸秆还田模式对作物产量、氮肥利用率、秸秆增产率、秸秆边际产量和秸秆农学利用率的影响。结果表明：秸秆还田均增加水稻产量,其中RS和WRS模式增产效果均显著大于WS模式;小麦产量随秸秆还田年限呈“减产-稳产-增产”的变化趋势。秸秆的周年增产率和农学利用率分别为5.65%~13.60%和0.11~0.17kg/kg。与RS模式相比,WRS模式属于秸秆过量还田,其秸秆增产效率降低。秸秆还田提高稻麦氮肥周年利用率1.67~4.01kg/kg,其中RS和WRS模式较WS模式更利于作物的氮吸收。WS、RS和WRS模式的稻田周年净收益较不还田模式分别增加1 690、4 875和4 177元/（hm²·年）,其中RS和WRS模式均显著高于WS模式。综合以上结果,麦季稻秸还田模式（RS）既可提高还田秸秆利用率,又可增加稻田净收益,推荐在稻麦两熟农田采用。     

四唑虫酰胺对棉田斜纹夜蛾的防治效果

【目的】研究双酰胺类杀虫剂四唑虫酰胺对斜纹夜蛾的室内生测和田间药效试验。【方法】采用人工饲料混药法测定四唑虫酰胺对斜纹夜蛾3龄幼虫毒力,采用机率值分析方法对数据进行处理,用SAS统计分析系统计算毒力回归方程和LD₅₀。用喷洒药剂悬浮液的方法进行田间试验,使用邓肯新复极差法(DMRT)对不同处理防治效果进行统计分析。【结果】四唑虫酰胺对斜纹夜蛾的LD₅₀为0.58 μg/g,氯虫苯甲酰胺对斜纹夜蛾的LD₅₀为1.12 μg/g,四唑虫酰胺的杀虫活性较高,但与氯虫苯甲酰胺的差异不显著。药后3 d,18%四唑虫酰胺悬浮剂7.5和10 mL/667m²处理对斜纹夜蛾的防效分别为85.00%和87.87%,显著高于5.0 mL/667m² 药剂处理,与5%氯虫苯甲酰胺悬浮剂 45 mL/667m²处理差异不显著。药后7 d,18%四唑虫酰胺悬浮剂 3个浓度处理对斜纹夜蛾的防效与5%氯虫苯甲酰胺 45 mL/667m²处理差异不显著。药后 14 d,18%四唑虫酰胺悬浮剂10 mL/667m²处理的防效显著高于5.0和7.5 mL/667m²药剂处理,但与5%氯虫苯甲酰胺 45 mL/667m²处理差异不显著。【结论】18%四唑虫酰胺悬浮剂对斜纹夜蛾具有良好的的防治效果,且随着浓度增高其防效增大。     

小麦秸秆还田条件下钾肥减量对水稻产量及养分利用的影响

利用长江中下游稻麦轮作定位试验，研究小麦秸秆还田条件下，钾肥减量施用对土壤钾素含量、水稻产量和钾素累积量以及钾肥利用率的影响，为小麦秸秆还田后水稻钾肥合理施用提供科学依据。试验共设5个处理，分别为：秸秆还田+配方施肥（K_100%），秸秆还田+配方施肥钾肥减量10%（K_90%），秸秆还田+配方施肥钾肥减量20%（K_80%），秸秆还田+配方施肥钾肥减量30%（K_70%），秸秆还田+配方施肥不施钾肥（K₀）。采集3年水稻不同生育期植株和土壤样品，分析土壤钾素动态变化和水稻钾素吸收富集规律，并统计水稻产量和经济效益。3年试验结果表明，与K_100%相比，K_90%处理的土壤全钾和速效钾含量分别提高了3.13%和6.38%，水稻钾素总累积量和净累积量平均提高1.55%和5.13%，水稻平均增产2.19%；K_80%和K_70%处理的土壤全钾和速效钾含量分别平均减少12.58%~15.31%和4.26%~10.64%，水稻钾素总累积量平均减少了7.49%~13.62%，水稻净累积量平均增加了0.48%~1.78%，K_80%处理的水稻产量平均增加2.32%，而K_70%处理的水稻产量则平均降低了6.43%。与K_100%相比，钾肥减量（K_90%、K_80%、K_70%）能够显著增加水稻钾肥农学效率（15.51%~24.53%）、偏生产力（17.96%~25.40%）和钾素吸收利用率（17.53%~55.36%）（P<0.05）。当钾肥减量大于20%时，经济效益呈下降趋势。小麦秸秆还田条件下，与配方施肥相比（K_100%），钾肥减量10%对土壤速效钾含量影响不显著，但能够提高水稻钾素累积量；钾肥减量20%~30%会降低土壤速效钾含量以及水稻钾素累积量，提高水稻钾素净累积量；钾肥减量10%~20%对水稻产量影响不显著，但可以增加钾肥农学效率、偏生产力和钾肥吸收利用率及经济效益。     

Effect of Aquasorb and Organic Compost Amendments on Soil Water Retention and Evaporation with Different Evaporation Potentials and Soil Textures

Abstract

Aquasorb PR3005A, a hydrophilic polymer (a salt copolymer polyacrylamide), and garden waste compost were added to a loamy sand and a loam soil in pots to assess their impact upon soil physical properties at two different evaporation potentials. Compost was mulched and incorporated, the Aquasorb was incorporated, and their effect on temperature and amelioration of soil water content and evaporation was investigated. Mulching with compost reduced evaporation and increased soil temperature. Maize (Zea mays var. single cross 704) was sown in the same pots later, and growth indicator factors (plant height, fresh and dry weight, root weight, and leaf area) were compared. It was concluded that compost mulch application is beneficial to soil water retention whereas compost incorporation did not show these benefits. Compost mulch advances seedling emergence and enhances early growth through hydrologic soil amelioration. High rates of Aquasorb were also beneficial in advancing the emergence and early growth of maize seeded in loamy sand. The hydration capacity of Aquasorb is reduced as the electrolyte concentration and electrical conductivity are increased. Increased electrolyte concentration in soil solution, through drying, may result in gel dehydration and water release at potentials greater than field capacity, which may be lost to drainage. Furthermore, it is concluded that pot experiments with amendments fail to simulate field conditions.     

Quantitative structure—activity studies of insect growth regulators. XI. Stimulation and inhibition of N-acetylglucosamine incorporation in a cultured integument system by substituted N-tert-butyl-N,N′-dibenzoylhydrazines

The ability to stimulate N-acetylglucosamine (GluNAc) incorporation in-vitro of a number of N-tert-butyl-N,N′-dibenzoylhydrazines having various substituents on both phenyl rings was measured in cultured integument excised from the rice stem borer (Chilo suppressalis Walker). The relationship between in-vitro and larvicidal potency was approximately linear. The substituent effects on variations in the potency were similar between in-vitro and larvicidal activities. An inhibitor of oxidative detoxication, piperonyl butoxide, had no synergistic effects on the in-vitro potency. The ability of some dibenzoylhydrazines to inhibit GluNAc incorporation at exposure periods longer than the optimum for stimulation was also measured in a similar cultured integument system. The relationship between the inhibitory and stimulatory potency indices was linear, indicating that the larvicidal activity of dibenzoylhydrazines is closely related to its ability to stimulate as well as to inhibit GluNAc incorporation into the larval cuticle.     

黄芪多糖对雏鸡外周血T淋巴细胞转化功能的影响

将１０８只１日龄伊莎系蛋用公雏均分为３组：一组为对照,其余２组在３日龄时,于背侧颈部皮下分别注射０．２、０．４ｍＬ黄芪多糖注射液（０．０１ｇ／ｍＬ）１次,再分别于７、２１、３５、４９日龄时采用ＭＴＴ比色法及微量全血培养３Ｈ－ＴｄＲ掺入法检测外周血Ｔ淋巴细胞转化率的动态变化。结果表明,黄芪多糖对２１、３５日龄雏鸡Ｔ淋巴细胞转化功能有增强作用,且与剂量有相关性,而对７、４９日龄雏鸡的作用不明显。ＭＴＴ比色法与３Ｈ－ＴｄＲ掺入法的检测结果无显著差异（Ｐ＜０．０５）。     

Burial rates of surrogate seeds in arable fields

The probability of seed consumption by surface-dwelling predators depends on the duration of seed exposure on the soil surface. We investigated seed burial using painted ceramic beads as surrogate seeds. Fifty beads of three size classes each were applied to small arenas within crop fields and their fates were followed from August to October. New sets of beads were applied as soon as most beads had disappeared from the soil surface. Bead availability on the soil surface declined immediately after placement, and then declined steadily over time, with increased loss during rain and management practices. Smaller beads were incorporated into the soil/litter matrix more easily than larger beads. Bead burial differed considerably among crop environments, with more burial in forage crops (red clover, lucerne) than in row crops (soyabean, maize). The fact that seed availability differed among crop environments suggests that it can be manipulated to maximise predation risk.     

麦秸还田及氮肥管理技术对水稻产量的影响

以水稻武香粳14和扬粳9538为材,大田设麦秸还田与不还田、不施氮肥、习惯施肥法（FFP）和基于叶绿素仪(SPAD)测定值的氮肥管理(SSNM)等处理。结果表明,SSNM较FFP氮肥施用量减少40.0%~41.7%,而产量平均增加3.81%。秸秆还田的较秸秆未还田的产量平均增加2.49%。氮肥的农学利用率、吸收利用率和生理利用率均以秸秆还田高于秸秆不还田处理。与秸秆未还田或FFP相比,秸秆还田和SSNM降低了生育前期的分蘖数、叶面积指数和干物质积累（但抽穗及以后差异较小）;提高了茎蘖成穗率、结实期叶片光合速率和根系活力。说明秸秆还田和SSNM有利于生育后期群体光合生产和提高物质生产效率。秸秆还田和实地氮肥管理提高了氮收获指数和氮肥利用效率。对秸秆还田和SSNM的产量、生育特性及氮肥利用效率进行了讨论。     

Weed control and sesame (Sesamum indicum L.) response to preplant incorporated herbicides and method of incorporation

Field studies were conducted at two sesame-growing regions of Texas in 2004 and 2005 to determine weed control and sesame response to four dinitroaniline herbicides and their method of incorporation. Ethalfluralin, pendimethalin (formulated as Prowl EC), and trifluralin were applied at the X, 1X, and 2X of the suggested label dose for Gossypium hirsutum L. Pendimethalin (formulated as Prowl H₂O) was applied at the X, 1X, and 1X rate. Two methods of incorporation included rolling cultivator mixing wheels and spring tooth harrow. With rolling cultivator mixing wheels, all herbicides controlled Amaranthus tuberculatus (Moq.) J.D. Sauer at least 74% regardless of dose. The X dose of ethalfluralin and pendimethalin (formulated as Prowl EC), or the X and 1X dose of pendimethalin (formulated as Prowl H₂O) controlled Brachiaria platyphylla (Griseb.) Nash no better than 73% while all other doses of the herbicides controlled B. platyphylla at least 80%. The use of mixing wheels to incorporate the herbicides resulted in better sesame stands and less stunting than the use of the spring tooth harrow; however, sesame stands were reduced as herbicide rate increased when using mixing wheels. Ethalfluralin at the 1X dose, pendimethalin (formulated as Prowl H₂O) at the X dose, and trifluralin at the X dose produced the highest sesame yield while ethalfluralin at the 2X dose produced the lowest yield.