不同小麦种植体系中磺酰磺隆在土壤中的持久性研究

Many sulfonylurea herbicides have been used under a wide variety of agronomic conditions in numerous crops. An understanding of dissipation rate of herbicide is fundamental for predicting the fate of herbicide in soil. In order to study the sulfosulfuron persistence under different cultivation systems of wheat, a four replicated experiment was carried out in the Hashemabad Reaserch Center of Gorgan, Iran in 2010 in a split plot design with two factors. Cultivation system as the main factor consisted of six levels, including conservation tillage by Combinate, no-tillage by Baldan grain drill, conservation tillage by Chizelpacker, conservation tillage by Delta Model, surface tillage by heavy disk, and conventional tillage by moldboard plow and twice disk. Secondary factor included two levels of sulfosulfuron application(with and without sulfosulfuron). Soil samples were taken at 6 stages and soil microbial respiration and soil pH were measured as factors affecting sulfosulfuron persistence. Results showed the least time of sulfosulfuron persistence belonged to the cultivation system of no-tillage by Baldan grain drill with a half-life of 4.62 d. Then, conservation tillage by Combinate and conventional tillage with a half-life of 6.30 d and conservation tillage by Delta Model with a half-life of 9.90 d were ordered. The most time of sulfosulfuron persistence(11.55 d) was related to conservation tillage by Chizelpacker. Ninety percent reduction of sulfosulfuron concentration occurred 15.34, 20.92, 32.88, and 36.38 d after sulfosulfuron application, respectively, for no-tillage system, conservation tillage by Combinate and conventional tillage, conservation tillage by Delta Model and surface tillage, and conservation tillage by Chizelpacker. In all the cultivation systems, toxicity symptoms were not observed 40 d after spraying sulfosulfuron onto the tomato plants which were used as test plant. Effects of different cultivation systems on soil microbial respiration were also significant.     

Development,growth, and nitrogen use of autumn- and spring-sown facultative wheat

Spring-sown crops are expected to have a higher risk of drought during summer in the next decades in Central Europe due to expected climate change. Therefore, a two-year experiment was conducted under Pannonian growing conditions in Eastern Austria to investigate the effect of autumn- and spring-sowing of facultative wheat. Autumn-sowing of facultative wheat enhanced crop development, soil coverage, crop stand height, crop growth rate, and nitrogen (N) utilization efficiency during the vegetation period compared to spring-sowing; duration of growth stages was prolonged and crops were earlier ripe. In contrast, spring-sowing resulted in higher relative growth rates, higher N concentrations of aboveground dry matter, higher relative N uptake rates, and more mineral N in the soil. At harvest, grain yield and yield components ears m^?2 and thousand kernel weight (TKW) were higher in autumn-sown than in spring-sown wheat, resulting thereby in an increased seed yield. Spring-sown wheat had higher N concentrations in grain and in straw. Anyhow, N yield was slightly higher with autumn-sowing due to the higher grain and straw yields. Grain and straw yield, plant stand height, ears m^?2, and TKW were impaired in the second experimental year by a severe drought for both sowing dates as well as N concentrations and N yields of grain and straw, partial factor N use efficiency and N utilization efficiency. But the yield components harvest index, grains m^?2, and grains ear^?1 were strongly impaired with spring-sowing under drought conditions. Thus, autumn-sowing of wheat resulted in higher yield stability across both years, based on these yield components highlighting possible benefits of autumn-sowing with expected summer drought under climate change.     

潮土小麦和玉米Olsen-P农学阈值及其差异分析

【目的】磷农学阈值是指导不同作物磷肥用量并获取最佳经济产量的重要依据,然而,不同地区不同的耕作制度、土壤类型、作物种类、pH、温湿度条件下,作物的磷农学阈值不同。明确小麦–玉米轮作体系下,典型潮土区小麦和玉米的磷农学阈值,并分析其差异。【方法】本研究基于“国家潮土土壤肥力与肥料效益长期监测站”25年的定位试验,选取氮、钾肥施用充足和磷肥用量不同的NK (不施磷肥)、NPK (施用氮磷钾化肥)、NPKM (氮磷钾化肥和有机肥配施)、1.5NPKM (高量氮磷钾化肥配施有机肥)、NPKS (氮磷钾化肥与玉米秸秆还田配施) 5个处理的试验数据,使用米切里西指数模型 (Mitscherlich exponential model) 拟合小麦和玉米的Olsen-P农学阈值,并通过对比不同土壤磷水平下两种作物的磷吸收利用特性,分析其阈值不同的原因。【结果】获得最大相对产量的95%时,潮土区小麦Olsen-P农学阈值为13.1 mg/kg,玉米Olsen-P农学阈值为7.5 mg/kg。玉米Olsen-P农学阈值低于小麦主要原因:1) 土壤磷水平较低时,小麦对磷缺乏更为敏感,而玉米可保持相对较强的吸磷能力,25年不施磷处理玉米吸磷量是小麦的1.4倍;2) 土壤Olsen-P含量达到玉米阈值,而未能达到小麦阈值时,可保障玉米籽粒、茎秆及小麦籽粒正常生长对磷的需求,但小麦茎秆磷浓度仅能达到相对最大磷浓度的68.9%,严重影响了小麦的正常生长和获取较高产量的能力;土壤Olsen-P含量提高到小麦阈值后,小麦茎秆磷浓度提高到相对最大磷浓度的80.5%以上,进而可保障小麦获得较高的产量;3) 土壤磷素养分充足时,小麦对磷的吸收量大于玉米,且主要是由于小麦茎秆磷浓度和吸磷量随土壤Olsen-P含量的增加而大幅度增加。【结论】小麦和玉米作为典型潮土区两种重要的粮食作物,Olsen-P农学阈值分别为13.1和7.5 mg/kg。由于两种作物的生理特性不同,小麦对磷素的吸收利用率较低,茎秆需要较高的土壤磷浓度维持正常生长,产量形成对磷养分需求更大。因此,小麦–玉米轮作体系下,小麦的磷农学阈值更高,小麦季所需土壤磷供应量大于玉米季。为增强磷肥利用效率,减少磷肥投入量和土壤中磷素的过量累积,玉米季磷肥使用量应适当小于小麦季。当土壤Olsen-P水平高于作物磷农学阈值后,减少或短时间停止施用磷肥并不会对作物产量有明显影响。     

Effect of Crop Residue With and Without a Culture of Cellulolytic Fungi on Yield,NPK Uptake and Soil Fertility Under Rice-Wheat Cropping System

The field experiments were carried out at Indian Agricultural Research Institute, New Delhi during three crop cycles from 1996-97 to 1998-99 to study the effect of incorporation of wheat and rice residues with and without a culture of cellulolytic fungi Trichrus spiralis on grain and straw yields and NPK uptake of rice-wheat cropping system and organic C, available P and available K content of soil. Incorporation of residue of wheat, rice or both had no significant effect on individual grain and straw yields and N and P uptake of rice and wheat, but significantly increased total grain and straw yields and N and P uptake of rice-wheat cropping system. Cellulolytic culture had no additional advantage over crop residues. Incorporation of residue of wheat, rice or both significantly increased K uptake of both rice and wheat as this practice resulted in recycling of 90% of total K uptake by rice and wheat crops. Incorporation of crop residue also resulted in building up of organic C, available P and available K content in soil.     

Residue Decomposition and Fate of Nitrogen‐15 in a Wheat Crop under Different Previous Crops and Tillage Systems

Abstract

Nitrogen (N) management may be improved by a thorough understanding of the nutrient dynamics during previous‐crop residue decomposition and its impact on fertilizer N fate in the soil–plant system. An experiment was conducted in the Argentine Pampas to evaluate the effect of maize and soybean as previouscrops and plow‐till and no‐till methods on N dynamics and ¹⁵N‐labeled fertilizer uptake during a wheat growing season. Maize and soybean residues released N under both tillage treatments, but N release was faster from soybean residues and when residues were buried by tillage. Net immobilization of N on decomposing residues was not detected. A regression model that accounted for 92% of remaining N variability included time, previous crop, and tillage treatment as independent variables. The rapid residue decomposition with N release was attributed to the high temperatures of the agroecosystem. The recovery of ¹⁵N‐labeled fertilizer in the wheat crop, soil organic matter, and decomposing residues was not statistically different between previous crop treatments or tillage systems. Crop uptake of fertilizer N averaged 52% across treatments. Forty percent of fertilizer N was removed in grains. Immobilization of labeled N on soil organic matter was substantial, averaging 34% of the ¹⁵N‐labeled fertilizer retained, but was very small on decomposing residues, averaging 0.2–3.0%. Fertilizer N not accounted for at harvest in the soil–plant system was 12% and was ascribed to losses. Previous crop or tillage system had no impact on wheat yield, but when soybean was the previous crop, N content of grain and straw+roots increased. Discussion is presented on the potential availability of N retained in wheat straw, roots, and soil organic matter for future crops.     

Cultivation of wheat following pea and triticale/pea mixtures increases yields and nitrogen content

Abstract

An experiment was conducted in 2004–2007 at the University of Podlasie Zawady Experimental Station (52°06′N, 22°50′E), Siedlce, Poland, to examine the effect of either post-harvest residues or residues and straw of spring triticale (Triticale), field pea (Pisum sativum L.) and their mixtures containing the following proportions of both components: 75+25, 50+50, 25+75% on the subsequent crop of winter wheat (Triticum aestivum L.). A field experiment was designed as split-blocks with three replicates. Residue mass, straw mass as well as N, P, K, Ca and Mg amounts were determined in the residues and straw. The residue amount of spring triticale was the greatest. N, Ca and Mg amounts in the residues of spring triticale/field pea mixtures were similar or higher whereas P and K amounts were similar or lower compared with spring triticale residues. Spring triticale straw contained less N, P, Ca and Mg than the straw of either field pea or spring triticale/field pea mixtures. Grain yield, yield components, N content and N uptake in the grain of winter wheat following field pea and spring triticale/field pea mixtures were significantly higher compared with winter wheat following spring triticale. Increasing proportions of field pea in mixtures with spring triticale cultivated as previous crops significantly increased winter wheat grain yields as well as N content and uptake. The residues of the previous crops combined with the straw significantly increased winter wheat grain yield, number of ears per m², number of grains in an ear, thousand-grain weight and N content and uptake. The highest winter wheat grain yield and N uptake were determined following an application of residues and straw of field pea and 25+75% spring triticale/field pea mixture. The grain of winter wheat after field pea had the greatest N content.     

绿洲灌区小麦免耕秸秆还田对后作玉米产量性能指标的影响

产量性能是决定作物生长发育和产量形成的关键因素,研究前茬秸秆处理方式对后茬作物产量性能指标的影响,对于建立高效种植制度、优化栽培措施具有重要指导意义。2009—2012年,在甘肃河西绿洲灌区,通过田间定位试验,研究了前茬小麦不同秸秆还田和耕作措施(NTSS:25 cm高茬收割立茬免耕;NTS:25 cm高茬等量秸秆覆盖免耕;TIS:25 cm高茬等量秸秆翻耕;CT:不留茬翻耕对照)对后作玉米产量性能指标的影响,以期为优化试区玉米种植模式提供依据。结果表明,与CT相比,前茬小麦秸秆还田降低了后作玉米大喇叭口期之前的叶面积指数(LAI)与光合势(LAD),但增大了吐丝期之后的LAI与LAD,延缓了衰老,以NTSS、NTS延缓衰老作用突出;NTSS、NTS和TIS处理玉米全生育期的平均叶面积指数(MLAI)比CT分别提高12.8%、19.1%和7.0%,总光合势分别提高12.9%、18.6%和6.8%,免耕秸秆还田(NTSS和NTS)提高MLAI和LAD的效果最好。免耕秸秆还田提高了玉米全生育期的平均净同化率(MNAR),以NTSS提高作用明显,较CT高10.7%;但净同化率(NAR)表现为吐丝期之前增大,吐丝期之后降低。NTSS、NTS提高了后作玉米的籽粒产量,比CT分别高13.0%、15.6%,TIS比CT提高7.9%,NTS增产效应最大。不同秸秆还田及耕作方式下,玉米籽粒产量与MLAI、穗数(EN)、穗粒数(KNE)呈极显著正相关性,与收获指数(HI)呈显著正相关性,但与MNAR无显著相关性。MLAI、EN、KNE增加、HI提高是前茬小麦免耕秸秆还田提高后作玉米产量的主要原因。前茬秸秆免耕还田优化后茬玉米主要产量性能指标的效果最好。因此,前茬小麦25 cm秸秆覆盖免耕还田是绿洲灌区优化后作玉米产量性能指标及获得高产的可行栽培措施。     

Yields of wheat and soil carbon and nitrogen contents following long-term incorporation of barley straw and ryegrass catch crops

Abstract. Three successive crops of winter wheat were grown on a sandy loam to test the residual effect of long‐term annual incorporation of spring barley straw at rates of 0, 4, 8 and 12 t ha^?1, and ryegrass catch crops with or without additions of pig slurry. Soil receiving 4, 8 and 12 t ha^?1 of straw annually for 18 years contained 12, 21 and 30% more carbon (C), respectively, than soil with straw removal, and soil C and nitrogen (N) contents increased linearly with straw rate. The soil retained 14% of the straw C and 37% of the straw N. Ryegrass catch‐cropping for 10 years also increased soil C and N concentrations, whereas the effect of pig slurry was insignificant. Grain yield in the first wheat crop showed an average dry matter (DM) increase of 0.7 t ha^?1 after treatment with 8 and 12 t straw ha^?1. In the two subsequent wheat crops, grain yield increased by 0.2–0.3 t DM ha^?1 after 8 and 12 t straw ha^?1. No grain yield increases were found after 4 t straw ha^?1 in any of the three years. Previous ryegrass catch crops increased yields of wheat grain, but effects in the third wheat crop were significant only where ryegrass had been combined with pig slurry. Straw incorporation increased the N offtake in the first wheat crop. In the second crop, only 8 and 12 t straw ha^?1 improved wheat N offtake, while the N offtake in the third wheat crop was unaffected. Ryegrass catch crops increased N offtake in the first and second wheat crop. Again, a positive effect in the third crop was seen only when ryegrass was combined with slurry. Long‐term, annual incorporation of straw and ryegrass catch crops provided a clear and relatively persistent increase in soil organic matter levels, whereas the positive effects on the yield of subsequent wheat crops were modest and transient.     

Responses of wheat to arbuscular mycorrhizal fungi: A meta-analysis of field studies from 1975 to 2013

Arbuscular mycorrhizal fungi (AMF) can benefit growth and yield of agriculturally significant crops by increasing mineral nutrient uptake, disease resistance and drought tolerance of plants. We conducted a meta-analysis of 38 published field trials with 333 observations to determine the effects of inoculation and root colonization by inoculated and non-inoculated (resident) AMF on P, N and Zn uptake, growth and grain yield of wheat. Field AMF inoculation increased aboveground biomass, grain yield, harvest index, aboveground biomass P concentration and content, straw P content, aboveground biomass N concentration and content, grain N content and grain Zn concentration. Grain yield was positively correlated with root AMF colonization rate, whereas straw biomass was negatively correlated. The most important drivers of wheat growth response to AMF were organic matter concentration, pH, total N and available P concentration, and texture of soil, as well as climate and the AMF species inoculated. Analysis showed that AMF inoculation of wheat in field conditions can be an effective agronomic practice, although its economic profitability should still be addressed for large-scale applications in sustainable cropping systems.     

轮作模式与周期对黄土高原旱地小麦产量、养分吸收和土壤肥力的影响

【目的】粮草轮作、粮豆轮作是黄土高原旱地区常见种植制度,本文利用长期定位试验探索该地区轮作制度和茬口年限对小麦产量、养分吸收和土壤肥力的影响,以期优化旱地作物种植制度。【方法】长期定位试验始于1984年,试验设8个处理:对照(小麦连作,CK),粮草长周期轮作(3组种植方式:2茬小麦→4茬苜蓿→1茬马铃薯→小麦,WAT1;小麦→4茬苜蓿→1茬马铃薯→2茬小麦,WAT2;4茬苜蓿→马铃薯→3茬小麦,WAT3),粮草短周期轮作(2组种植方式:小麦+红豆草→红豆草→小麦,WST1;红豆草→小麦→小麦+红豆草,WST2),粮豆轮作(2组种植方式:小麦+糜子→豌豆→小麦,WPT1;豌豆→小麦→小麦+糜子,WPT2)。小区面积66.69 m2,每个处理重复3次,随机区组排列。小麦收获后采集植物及土壤样品,测定小麦产量、籽粒和秸秆养分含量、土壤肥力性质。【结果】与小麦连作相比,轮作小麦籽粒增产1.47%~29.66%,秸秆增产2.17%~29.77%,粮草轮作增产效果更显著,轮作优势在豆科牧草后第二年最高,第三年减弱。粮草长周期轮作有利于小麦对N、K、Fe、Cu、Zn的吸收,吸收量在苜蓿茬后第三年第二年第一年;粮草短周期轮作可提高小麦对N、K、Fe的吸收量,红豆草茬后第1年吸收量稍高于后第二年;粮豆轮作有利于小麦吸收N、K、Fe、Mn,豌豆茬后第二年吸收量大于第一年。轮作制度和茬口年限对小麦微量元素养分收获指数的影响程度大于大量元素,粮豆轮作有利于N、P、Cu向籽粒转移,3种轮作制度下小麦K收获指数均低于连作小麦,粮草轮作中小麦Fe收获指数低于连作小麦。轮作后,土壤全氮增加11.54%~20.51%,碱解氮提高9.66%~21.56%;粮草短周期轮作对土壤有机质、氮素和速效钾的提升作用突出,但有效磷亏缺23.97%;粮豆轮作对土壤磷素累积和有效化作用明显,其有效磷比小麦连作增加45.52%。【结论】黄土高原旱地区增加小麦产量、改善籽粒矿质营养,实现土壤培肥的较优轮作模式为红豆草(2~4年)→小麦(2年),以4~6年为一个轮作周期,同时注意增施磷肥。     

A field study on the influence of soil ph on trace element levels in spring wheat (Triticum aestivum), potatoes (Solanum tuberosum) and carrots (Daucus carota)

Soil pH is one of the main factors influencing the solubility and availability of trace elements in arable soils. Thus pH can affect the trace element contents of agricultural crops and thereby indirectly influence human health. The aim of this study was to determine Cd, Ni, Zn, Cu, Mn, Cr, Al and Se contents in spring wheat, potatoes and carrots (Cd, Ni and Zn) and estimate their correlations with certain soil factors (surface and subsurface soil pH and organic matter content) governing the plant availability of these elements. Commercial fields were sampled in Sweden in order to cover a wide range of soil types with respect to pH, soil texture and organic matter content. Concentrations of Zn, Mn, Ni (grain) and Cd (straw) in spring wheat (n=43); Cd, Ni, Zn, Mn, Cu and Al in potatoes (n=69); and Cd, Ni and Zn in carrots (n=36) showed significant negative correlations with surface soil pH (0–25 cm). The Se content of potatoes and Cr content of spring wheat straw were positively correlated with soil pH. Stepwise multiple regressions including a combination of soil pHs (0–25 and 25–50 cm) and organic matter contents (0–25 cm) showed that the organic matter content as well as the surface and subsurface soil pH significantly influenced concentrations of several trace elements in one or more of the studied crops. It was concluded that, if acid deposition together with other acidifying processes (fertilisation, harvest of biomass, etc.) are not balanced by a sufficient amount of liming there might be a decrease in the pH of arable soils, which, in turn will lead to decreased levels of Se in edible crops but an overall increase concentrations of other trace elements.     

Effect of crop‐residue management on the production and agronomic nitrogen efficiency in a rice–wheat cropping system

The rice–wheat cropping system (RWCS), producing about 5–10 Mg ha^–1 y^–1 of grain, is the backbone of food‐crop production in South‐East Asia. However, this system shows signs of fatigue as indicated by declining yields, negative nitrogen (N) balances, and reduced responses to applied fertilizer at some research centers. The return of rice and wheat residues can recycle up to 20%–30% of the N absorbed by the crops. However, their wide C : N ratio can temporarily immobilize native and applied N. To overcome this immobilization, wheat‐straw application was supplemented with the incorporation of Sesbania green manure and mungbean residues, and their effects on productivity, agronomic N efficiency, and system's apparent N balances were studied. Combining the application of wheat straw with Sesbania green manure or mungbean residues increased cereal grain yield and agronomic N efficiency and improved the generally negative apparent N balances. The combined use of wheat straw and mungbean produced an additional 0.5–0.6 t ha^–1 protein‐rich grain and thus appears to be the most promising residue‐management option for rice–wheat cropping systems in South Asia, provided that the transition cropping season between wheat harvest and rice transplanting is long enough.     

稻麦玉米秸秆残留还田量定量估算方法及应用

为了解秸秆残留还田是秸秆直接还田的基本形式。该文通过逐步推导,给出了秸秆残留还田量定量估算的系列公式,并将秸秆残留还田量定量估算建立在5个参数的基础上,即农作物平均株高、收割留茬高度、叶部生物量比例、枝叶脱落率和秸秆机械收集损失率;以实地调查为基础,结合对试验数据收集整理,给出了小麦、玉米、水稻三大农作物秸秆残留还田量定量估算的参数体系,并估算出了三大农作物的秸秆残留还田量,分别为7 106.92、4 543.48和6 392.95万t,合计为18 043.35万t,占三大农作物的秸秆总产量的31.13%;三大作物人工收获秸秆残留还田量为1724.47万t,机械收获秸秆残留还田量为16 318.88万t,后者是前者的9.46倍;进而以农作物面积为权重,推算出全国的秸秆残留还田量为25 330.08万t,计算出单位面积耕地的残留还田量为1.87 t/hm2,与基本还田量的最低需求3.0 t/hm2相比尚需增加60%以上,与基本还田量的一般需求4.5 t/hm2相比尚需增加1.41倍。论文最后指出了秸秆残留还田量定量估算需要继续深入开展的主要研究工作:一是开展更广泛的田间实测,进一步提高小麦、玉米、水稻三大农作物秸秆残留还田量定量估算参数的精准度,尤其是收割留茬高度和秸秆机械收集损失率这两大参数的精准度,以便更确切地估算三大农作物的秸秆残留还田量;二是针对棉花、大豆、油菜等主要经济作物进行秸秆残留还田量定量估算研究,建立全国主要粮经作物秸秆残留还田量定量估算的参数体系;三是建立区域性的秸秆残留还田量定量估算的参数体系,逐步实现各区域秸秆残留还田量的定量估算。     

Effect of addition of organic residues,farmyard manure and fertilizer nitrogen on soil fertility in rice‐wheat cropping system

A field experiment was conducted for 3 crop years (July‐June) at the Indian Agricultural Research Institute, New Delhi to study the effects of Sesbania and cowpea green manuring (GM) and incorporation of mungbean residues after harvesting grain, Leucaena loppings, FYM and wheat straw incorporation before planting rice and application of 0,40,80 and 120 kg N ha^?1 to rice on the soil organic carbon (SOC), alkaline permanganate oxidizable N (APO‐N), 0.5 M sodium bicarbonate extractable P (SBC‐P) and 1N ammonium acetate exchangeable K (AAE‐K) in surface 0–15 cm soil after the harvest of rice and wheat grown in sequence. Green manuring and addition of organic residues prevented the decline in SOC. On the other hand addition of N fertilizer tended to decrease SOC after rice harvest. On the contrary application of green manures, organic residues, FYM and fertilizer N increased APO‐N, which indicates the benefit of these treatments to a more labile soil organic N pool. Also application of green manures, organic residues, FYM and fertilizer N increased SBC‐P. Not much change was observed in AAE‐K by the treatments applied.     

Nitrogen and carbon mineralization of surface-applied and incorporated winter wheat and peanut residues

Laboratory incubation experiments were conducted to study the C and N mineralization dynamics of crop residues (fine roots and straw) of the two main crops (winter wheat and peanut) in the Chinese Loess Plateau under different ways of incorporation. The C mineralization patterns of the soil amended with winter wheat residues differed greatly, and the highest C mineralization was observed in the treatment with winter wheat straw incorporated (39% of the total added C mineralized). The way of straw placement had only a minor effect on the pattern of C mineralization for peanut. Generally, winter wheat residues showed a stronger immobilization than peanut residues during the incubation period, without any net N release. Winter wheat straw incorporated showed the strongest N immobilization with 35 mg kg⁻¹ (equivalent to 27% of added N) immobilized at the eighth week. This study indicated that retaining crop residues at the soil surface in the dry land soils of the Chinese Loess Plateau is beneficial for C sequestration. It also showed that N immobilization occurs only during a limited period of time, sufficient to prevent part of the mineral N pool from leaching, and that net N mineralization can be expected during the subsequent cropping season, thus enhancing synchronization of N supply and demand.     

南方设施菜地填闲苋菜筛选及其氮磷淋失阻控效果研究

筛选经济效益高、易推广,且对夏季休闲期氮磷淋失阻控效果好的填闲作物,对减轻我国珠三角地区设施菜地土壤氮磷流失、保护水体环境具有重要意义.通过淋溶管法研究了夏季休闲期(7月至8月)种植4种苋菜(圆红苋菜、心红苋菜、青苋与南星苋)对设施菜地土壤淋溶液pH、无机氮磷浓度及收获后土壤速效养分等的影响.结果表明:苋菜作为填闲作物...     

Selection Criteria for Genotypes and Identification of Plant Characteristics for Phosphorus-Efficient Wheat

Most genetic analyses of wheat crops concentrate on elucidating the mode of inheritance of plant characteristics. However, it is equally important to study the genetic relationship between different characteristics so that the consequences of selection for one characteristic on the performance of another can be predicted. Three field experiments with 15 wheat genotypes were conducted at two sites with similar soil types and agroecological conditions (two experiments at site 1 and one experiment at site 2) to evaluate wheat genotypes through correlation and path analyses for identification of plant characteristics responsible for high grain yield at low phosphorus (P) (7.86–8.23 mg P kg^?1 soil; control, no application of P) and adequate P (52 kg P ha^?1) in soil. On the average of the three experiments, the genotypic and phenotypic coefficients in correlation analysis agreed closely in each case. Relatively high values of genotypic coefficient showed a masking influence of genetic factors in the grain production. Grain yield correlated significantly with P-uptake parameters, such as P uptake in grain and straw. Integration of P in grain formation varied among wheat genotypes because of differences in their abilities to absorb, translocate, distribute, accumulate, and utilize P. The integrated effect of these physiological processes appeared in the form of end product (i.e., grain). The yield potential of a genotype to produce grain can be measured directly from absolute grain yield, but when selection was made through the involvement of plant factors such as harvest index, it proved to be a good predictor of grain yield. Positive relationship of harvest index with grain yield indicated an increase in grain yield. Because grain production is an outcome of the integrated effect of many P-related physiological processes, P efficiency was measured by P harvest index, P efficiency ratio, and P physiological efficiency index. The P physiological efficiency index was found to be an appropriate measure of P-use efficiency. When the selection was made through path analysis, it was observed that the genotypes that had high harvest index, absorbed more P, accumulated more P in grain, and produced more grain per unit of absorbed P were efficient in P use and produced high grain yield under low available soil P field conditions. Wheat genotypes ‘Inqlab 91,’ ‘Pak 81,’ ‘4072,’ ‘4943,’ and ‘5039’ were capable of producing high grain yield under low soil P field conditions in this study.     

Influence of crop residue management, cropping system and N fertilizer on soil N and C dynamics and sustainable wheat (Triticum aestivum L.) production

Management of N is the key for sustainable and profitable wheat production in a low N soil. We report results of irrigated crop rotation experiment, conducted in the North West Frontier Province (NWFP), Pakistan, during 1999–2002 to evaluate effects of residue retention, fertilizer N application and mung bean (Vigna radiata) on crop and N yields of wheat and soil organic fertility in a mung bean–wheat sequence. Treatments were (a) crop residue retained (+residue) or (b) removed (−residue), (c) 120 kg N ha⁻¹ applied to wheat, (d) 160 kg N ha⁻¹ to maize or (e) no nitrogen applied. The cropping system was rotation of wheat with maize or wheat with mung bean. The experiment was laid out in a spit plot design. Postharvest incorporation of crop residues significantly (p < 0.05) increased the grain and straw yields of wheat during both years. On average, crop residues incorporation increased the wheat grain yield by 1.31 times and straw yield by 1.39 times. The wheat crop also responded strongly to the previous legume (mung bean) in terms of enhanced grain yield by 2.09 times and straw yield by 2.16 times over the previous cereal (maize) treatment. Application of fertilizer N to previous maize exerted strong carry over effect on grain (1.32 times) and straw yield (1.38 times) of the following wheat. Application of N fertilizer to current wheat produced on average 1.59 times more grain and 1.77 times more straw yield over the 0 N kg ha⁻¹ treatment. The N uptake in wheat grain and straw was increased 1.31 and 1.64 times by residues treatment, 2.08 and 2.49 times by mung bean and 1.71 and 1.86 times by fertilizer N applied to wheat, respectively. The soil mineral N was increased 1.23 times by residues, 1.34 times by mung bean and 2.49 times by the application of fertilizer N to wheat. Similarly, the soil organic C was increased 1.04-fold by residues, 1.08 times by mung bean and 1.00 times by the application of fertilizer N. We concluded that retention of residues, application of fertilizer N and involvement of legumes in crop rotation greatly improves the N economy of the cropping system and enhances crop productivity in low N soils.     

Persistence of sulfentrazone in soil under soybean and its carryover effect on bioindicators

To assess the persistence and dissipation kinetics of sulfentrazone in soil, terminal residues in soybean and carryover effect on bioindicator species, field experiment was carried out under Indian tropical conditions. The sulfentrazone was applied at 360, 480 and 720?g a.i. ha^?1 rates as pre-emergence herbicide. Its residues in soil and in soybean at harvest were analyzed by high pressure liquid chromatography. Results showed that the sulfentrazone dissipation in soil followed first-order reaction kinetics with the half-lives of 5.5 to 14.8 days. Terminal residue in shoot and grain showed that sulfentazone at 360?g ha^?1 can be safely applied for weed control in soybean since there was no phytotoxicity injury to the crop. The residue in soybean grain was within the safe limits (0.05?µg g^?1) as proposed by US. However, the detection of sulfentrazone residue in soil at harvest and carryover injury to bioindicator signified the risk for crops in succession. Hence the use of this herbicide in soil with low organic matter and coarse texture is questionable as it is highly mobile. Further biomagnifications of sulfentrazone residue in soil and crop produce under continuous use and interaction of climatic variables and soil properties on its persistence, sorption and leaching behavior need to be investigated.     

秸秆还田对冬小麦产量和氮、磷、钾吸收利用的影响

【目的】陕西关中平原是我国典型的冬小麦—夏玉米轮作区,冬小麦播种前将上季收获后的玉米秸秆还田是当地普遍采用的作物秸秆管理方式。本研究以优化秸秆还田条件的小麦养分资源管理,实现作物增产和肥料增效为目标,通过2年的田间定位试验,探索关中地区玉米秸秆还田条件下,冬小麦高产高效的最佳养分管理措施。【方法】试验于2011年10月至2013年5月在陕西省周至县终南镇进行,供试冬小麦品种为周麦23,夏玉米品种为郑单958。采用裂区设计,主处理为玉米秸秆全量还田(S1)和秸秆不还田(S0),副处理为5个不同氮肥施用水平(N 0、84、168、252和336 kg/hm2),种植作物为冬小麦。通过不同氮水平的回归分析,研究了玉米秸秆还田对后茬冬小麦的籽粒产量、生物量和收获期地上部氮、磷、钾养分吸收利用的影响。【结果】与玉米秸秆不还田相比,秸秆还田对冬小麦籽粒产量和收获期地上部氮、磷、钾养分吸收量的影响均表现出低氮降低、高氮增加的趋势。第一年和第二年在施氮量分别低于N 153和187 kg/hm2时,秸秆还田处理小麦减产,相反则增产,并且增产量随着氮肥用量的增加而增大;生物量与产量趋势一致,前后两年玉米秸秆还田与不还田条件下,冬小麦生物量相等时的氮肥用量分别为N 190和202 kg/hm2。在产量构成要素中,同一氮水平时,秸秆还田对小麦穗粒数和千粒重没有明显影响,而每公顷穗数却表现为低氮降低、高氮增加的趋势,所以秸秆还田后穗数增加是小麦增产的主要原因。同时,在玉米秸秆还田条件下,小麦地上部氮、磷、钾吸收量增加时,第一年的氮肥用量分别高于N 275、123和213kg/hm2,第二年分别高于N 200、165和241 kg/hm2,但氮、磷、钾的收获指数不随施氮量的增加而递增。而且过量施氮也会造成小麦籽粒磷含量的降低。【结论】在综合同一施氮水平时,秸秆还田后的冬小麦籽粒产量和地上部氮、磷、钾养分吸收利用的变化,建议在陕西关中平原的冬小麦—夏玉米轮作区域,氮肥用量应控制在N 150~200kg/hm2,以保证在玉米秸秆还田条件下小麦的增产和氮、磷、钾养分资源的高效合理利用。