Adsorption and desorption of atrazine, desethylatrazine, deisopropylatrazine, and hydroxyatrazine in vegetated filter strip and cultivated soil

Adsorption and desorption of atrazine and its metabolites in vegetated filter strip soil (VFS) has not been evaluated, yet these data are needed to predict the transport of these compounds through the VFS. Adsorption and desorption parameters for atrazine, desethylatrazine (DEA), deisopropylatrazine (DIA), and hydroxyatrazine (HA) were compared between a cultivated Houston Black clay (CS) and an adjacent 12-year-old VFS established in a mixed stand of bermudagrass [Cynodon dactylon (L.) Pers.] and buffalograss [Buchloe dactyloides (Nutt. Engelm)]. Adsorption and desorption isotherms were determined by batch equilibrium. The evaluated chemical and physical properties of the VFS and CS were similar with the exception of a 1.7-fold increase in the organic carbon content of the VFS. Adsorption and desorption coefficients for atrazine were at least 59% higher in VFS than in CS. The adsorption coefficient for HA was 48% higher in VFS compared with CS, but desorption was not statistically different between soils. Adsorption and desorption coefficients for DEA and DIA were not statistically different between soils. The predicted order of mobility in CS is HA < atrazine = DIA = DEA. In VFS, the predicted order of mobility is HA < atrazine = DIA < DEA. These data indicate that the higher organic carbon in VFS will likely retard the transport of atrazine and HA to surface and ground waters; however, the transport rates of DEA and DIA will be similar between soils.     

不同灌水对冬小麦农艺性状与水分利用效率的影响研究

试验研究不同灌水对 10个冬小麦品种农艺性状、产量和水分利用效率的影响结果表明 ,不同冬小麦品种对水分亏缺的响应规律基本相同 ,但品种间有一定差异 ,充分灌水处理冬小麦生物量较大且水分利用效率较低 ,而灌 2水 (拔节～抽穗水 )处理效果较佳 ,其中“6 36 5”抗旱性能和产量潜力最佳 ,水分利用效率也较高。     

秸秆带状覆盖下培土对马铃薯产量与水分利用效率的影响

气候变化效应评估、土壤固碳潜力和肥力管理等,迫切需要详尽的土壤有机质（soil organic matter, SOM）空间分布信息。该文以江苏省第二次土壤普查的1 519个典型土壤剖面的表层（0～20 cm）SOM含量为例,选择1 217个样本为建模集,302个为验证集,选取年均温度、年均降雨、物理性黏粒和土壤pH值等因子进行SOM的地理加权回归（geographically weighted regression, GWR）建模。从建模集中分别随机抽取100%（1 217个）、80%（973个）、60%（730个）、40%（486个）,20%（243个）的样点,对比不同样点数量下GWR和传统全局回归模型的精度差异,并选择最优模型进行SOM空间预测制图。结果表明：1）江苏省SOM含量在不同空间尺度上存在极显著的空间自相关性。不同样点数量的建模集的全局自相关性和局部空间自相关聚类图结果相似。全局Moran''s I值介于0.25～0.61（P<0.001）。SOM含量空间分布以空间聚集特征为主,"高-高"聚集区主要分布在苏中和苏南地区,"低-低"聚集区主要分布在苏北地区。2）GWR建模结果均优于传统的传统全局回归建模,其残差在不同的空间尺度上均不存在空间自相关性。不同建模集的GWR的R2adj较全局建模均提高0.15～0.20,其AIC和RSS均比全局模型有大幅降低,为56.08～360.19和17.40～76.67。不同建模样本数量的GWR模型对SOM的解释能力差异较小。3）建模样点数量（除建模样本n=243）对GWR预测制图结果的精度影响不大,RMSE介于5.56～5.75 g/kg之间,MAE介于3.87～4.05 g/kg之间,R2介于0.52～0.48之间,均优于全部建模样点的普通克里格插值验证结果。该研究可为样点数较少的省级尺度地区SOM空间建模与制图提供借鉴。     

Improving agricultural water use efficiency by nutrient management in crop plants

Abstract

Improvement of agricultural water use efficiency is of major concern with drought problems being one of the most important factors limiting grain production worldwide. Effective management of water for crop production in water-scarce areas requires efficient approaches. Increasing crop water use efficiency and drought tolerance by genetic improvement and physiological regulation may be a means to achieve efficient and effective use of water. A limited water supply inhibits the photosynthesis of plants, causes changes of chlorophyll contents and components and damage to photosynthetic apparatus. It also inhibits photochemical activities and decreases the activities of enzymes in plants. Water stress is one of the important factors inhibiting the growth and photosynthetic abilities of plants through disturbing the balance between the production of reactive oxygen species and the antioxidant defence, causing accumulation of reactive oxygen species which induce oxidative stress to proteins, membrane lipids and other cellular components. A number of approaches are being used to enhance water use efficiency and to minimize the detrimental effect of water stress in crop plants. Proper plant nutrition is a good strategy to enhance water use efficiency and productivity in crop plants. Plant nutrients play a very important role in enhancing water use efficiency under limited water supply. In this paper we discuss the possible effective techniques to improve water use efficiency and some macronutrients (nitrogen, phosphorus, potassium, calcium and magnesium), micronutrients (zinc, boron, iron, manganese, molybdenum and chloride), and silicon (a beneficial nutrient) in detail to show how these nutrients play their role in enhancing water use efficiency in crop plant.     

Adsorption efficiency of a continuous trapping system and its use for the collection of root exudates from cucumber

Root exudates comprising soluble low‐molecular‐weight organic compounds (LMWOCs) play a crucial role in the rhizosphere processes. Therefore, accurate determination of the composition and quantity of these compounds is of importance. A continuous trapping system (CTS) with XAD‐4 macroporous resin is widely used for collecting root exudates in hydroponics, and ion exchange resins are used in the separation of root exudates into neutral, acid and basic fractions. Here, we studied the adsorption equilibrium isotherms and dynamic adsorption properties of 27 standard LMWOCs on XAD‐4 resin. The adsorption isotherms of most LMWOCs matched the Langmuir isotherm equations. Furthermore, we investigated the adsorption efficiency of the CTS for LMWOCs and the recovery ratios during fractionation by ion exchange resins. The adsorption capacities of the CTS for LMWOCs which are non‐polar or having large non‐polar moieties were higher. The recovery ratios of most LMWOCs were larger than 80% during fractionation. The overall recovery ratios of LMWOCs were ca. 10, 20, and 30% for sugars, organic acids, and amino acids, respectively. Using this collection method, we present the composition and quantity of root exudates of cucumber (Cumumis sativus L.) at four different growth stages. The major components of root exudates were similar to previous works, whereas the quantities were different. The various collection methods may be the main reason for these differences. Therefore, it is necessary to study the overall recovery ratios when the compositions of root exudates via different collection methods are compared.     

基于遗传投影寻踪模型的农业水资源利用效率综合评价

针对农业水资源利用效率评价指标的不相容性问题,提出了农业水资源利用效率综合评价的遗传投影寻踪方法。该方法可以依据样本自身的数据特性寻求最佳投影方向,利用最佳投影方向可以判断各评价指标对综合评价目标的贡献大小和方向。通过最佳投影方向与评价指标的线性投影得到投影指标值,通过这一指标可以对样本进行统一评价和分类。利用该方法对甘肃省81个县域单元的农业水资源利用效率进行综合评价,评价结果很好的反映了各评价指标对综合评价目标的贡献大小和方向以及各评价单元综合利用效率。     

农地集约利用的碳排放效率分析与低碳优化

提高农地利用集约水平与控制农地利用碳排放量容易陷入两难选择的困境,理想的碳排放效率可以寻找到以碳排放作为成本,适度的农地利用集约水平。该文构建农地集约利用度计算模型与农地集约利用投入产出指标,计算中国31个省份的农地集约利用度;基于松弛测度(slacks-based measure,SBM)模型,构建SBM模型投入产出指标,计算各省份的农地集约利用碳排放总效率、技术效率与规模效率。研究结果表明:农地集约利用程度高低与农地集约利用碳排放总效率高低并不保持普遍一致;农地集约利用碳排放总效率有效省份集中分布在西部地区,农地集约利用度较高的长三角、珠三角、京津冀地区主要省份的农地集约利用碳排放总效率普遍较低;区域农地集约利用碳排放技术效率不足是导致总效率偏低的主要原因,而规模效率不足对总效率影响较小。因此针对总效率无效省份,给出调整投入冗余量、期望产出不足量与非期望产出冗余量的低碳优化方案,并构建结合了东、中、西部地区区域农地利用与经济发展特点的低碳优化策略,以期最终可以改善农地集约利用碳排放效率。     

农业生产资源投入效率的初步研究——以江苏省海安县为例

农业生产需要 3大类资源 :土地、劳动力、资本。本文通过对农业生产资源特性的分析 ,论述了我国农业生产资源投入的效率 ,并以江苏省海安县为例 ,测算了海安县农业生产资源投入的效率。     

Nitrogen balance in small river basins under agricultural and forestry use

The N balance has been studied in detail in the basins of small rivers under agricultural management and forest use. The N content of the watershed territory of large forests was found to be practically balanced. In the river basin where the land was intensively farmed for 10 yr, N input increased five times through mineral fertilizers, and one-and-a-half times through organic fertilizers. Consequently, the amount of N returned to the atmosphere as a result of denitrification increased by one-and-a-half times, and that leached into the ground water, increased from 0.8 to 6.5 mg 1^?1 N.     

Nitrogen use efficiency by winter barley under different climatic conditions

The proportion of straw and grain as well as of nitrogen (N) in the barley (Hordeum vulgare L.) plant was greatly changed by the distribution of rain in the pre‐ and post‐anthesis periods and by the existence of air temperatures above 30°C during grain filling along with N fertilizer rate. The response of barley to N rates of 0, 40, 80, 120, and 160 kg N/ha was studied over a three‐year period. Adequate rainfall in the pre‐anthesis period, little rain in the post‐anthesis period, and air temperatures above 30°C during the hard dough stage of the grain development, produced high N translocation to the grain as well as a positive response on grain yield and N content in the grain up to a fertilizer rate of 118 N kg/ha. Above this rate, grain yield decreased, while the N content in grain continued to increase. Optimum moisture conditions during the pre‐ and post‐anthesis periods, and mild temperatures during the grain filling period, produced a good grain yield response to N fertilizer rate, increases up to 131 kg N/ha without varying the N content in grain. The N translocation efficiency was somewhat lower than low rainfall in the post‐anthesis period. Low rainfall in the pre‐anthesis period and air temperatures above 30°C in the early milk stage of the grain made grain filling difficult, even when the rainfall was sufficient in the post‐anthesis period. Hence under these conditions, N fertilizer rate did not increase the grain yield, but the N content and the N‐translocation efficiency decreased with increasing N fertilizer rates.     

不同白菜品种对锌的响应及锌利用效率研究

采用盆栽试验研究了白菜[Brassica campestris L.ssp.Chinensis(L.)Makino]4个品种对不同浓度锌(Zn 0、1、10 mg/kg)的响应.结果表明,白菜的生物量及体内锌含量随锌水平的增加而增加;但白菜品种对锌营养反应的敏感性不同.地上部锌含量、锌积累量和锌吸收效率均以日本华冠(J...     

Air filter efficiency as a function of particle size and velocity

The air filtration theory demonstrates the existence of a minimum efficiency value for some aerosol particle sizes and velocities. Through experiments, many laboratories have sought to prove this efficiency minimum while using industrial filter pads. Generally used methods, involving monodisperse aerosol generation, are difficult to implement. The authors describe a laboratory experiment ready for semi-industrial application, thanks to the use of a new type of particle counter. A lightly poly dispersed soda-fluorescein (uranin) aerosol is used. Air filtration concepts are brought to mind and detailed experimental models are described, as well as findings with high-efficiency paper filters, alfa fiber filters, asbestos and fiberglass filters. Efficiency minimum occurs for 0.15 μm diameter sodafluorescein particles. Filtration velocity influence on efficiency is also demonstrated. Lastly, the authors compare known results with their soda-fluorescein aerosol and with sodium chloride aerosol findings.     

Enhancing the P trapping of pasture filter strips: successes and pitfalls in the use of water supply residue and polyacrylamide

In intensive pastoral systems the landscape at ground level is clad in dense, filtering vegetation – yet phosphorus losses in overland flow do occur, and pollution of surface waters is a serious consequence. The use of pre‐applied polyacrylamide (PAM) or chitosan to trap particulate phosphorus (PP) and P‐sorbing potable water treatment alum residue (PWTR) to enhance vegetative filtering effects is examined here using field and laboratory overland flow simulation (flows from 0.43 to 0.34 litres s^?1 (m width)^?1) and analysis. Fitted equations suggest that up to 40% of dissolved reactive P applied (0.75 mg P litre^?1) in overland flow could be captured in a flow length of 2.1 m (1 kg PWTR m^?2). Unfortunately, drying decreased PWTR effectiveness, though little of the P captured was readily desorbed. This effect did not appear to be the result of gibbsite formation. Compared with the other treatments, there was a strong treatment effect of pre‐applied PAM on the change in PP losses (P < 0.001) over time, though evidence suggests the PAM effect declined during a 44 minute flow period. We showed that the investigated two‐pronged approach to the enhancement of the effectiveness of P trapping by pasture had limitations. Laboratory sheet‐flow simulations suggest that a field‐stable P sorber with sorption characteristics similar to those of the un‐dried PWTR could be an effective retention enhancer for dissolved P. Pre‐applied PAM can have an effect on particulate‐P trapping but was rapidly dissolved and removed by flow.     

Run-off transport of herbicides during natural and simulated rainfall and its reduction by vegetated filter strips

The efficiency of filter strips in protecting watercourses against herbicides in run‐off was evaluated in field experiments in western Germany. Surface run‐off caused by natural rainfall and related transport of metolachlor, terbuthylazine and pendimethalin were measured on plots of 40 m length without filter strips (F0), and after passing over three types of herbicide‐untreated field margin: 12 m conservation headland (CH12), 6 m (GF6) and 12 m grass strips (GF12). Run‐off was also measured after simulated rainfall on 7 m long plots without (F0) and with 3 m grass strips (GF3). All three herbicides were transported both in dissolved and in adsorbed forms; the partitioning depended on their water solubility with metolachlor and terbuthylazine mainly translocated in dissolved form (F0: highest mean concentrations for a natural run‐off event 721 and 220 μg L^?1, respectively). Pendimethalin was predominantly transported in adsorbed form (maximum mean concentration 11.2 μg L^?1). In the sediment, the highest mean herbicide contents in a single natural event (F0) accounted for 2294 μg kg^?1 (metolachlor), 1317 μg kg^?1 (terbuthylazine) and 5648 μg kg^?1 (pendimethalin). The proportions of applied herbicide translocated were 0.3% (metolachlor), 0.2% (terbuthylazine) and 0.06% (pendimethalin; F0, natural rainfall). The extent of herbicide transport decreased with time but within this trend soil sealing, soil moisture and amount and intensity of rainfall increased losses. Compared with the F0 plots, the reduction of herbicide translocation after natural rainfall reached 80–83% (CH12), 80–88% (GF6) and >99% (GF12) over the 3‐year period. The 12 m grass strips allowed only one extreme run‐off event to pass through, thus providing a highly effective watercourse protection against herbicide pollution.     

Screening for intrinsic water use efficiency in a potato dihaploid mapping population under progressive drought conditions

A drought screening experiment focusing on intrinsic water use efficiency (WUE_i) was carried out among 132 clones belonging to a dihaploid potato mapping population. The clones were exposed to progressive soil drying during a five-day period in a greenhouse pot experiment. Analysis of the underlying variables was done based on a multivariate data analysis strategy. The strategy successfully divided the clones into WUE_i performance categories. Differences between clonal WUE_i responses were traced back to differences in the net photosynthetic rate. Stomatal conductance (g_s) did not vary significantly between the clones. Leaf abscisic acid (ABA) concentration and leaf water potential were found to reflect known isohydric behaviour for potato, and a non-linear relationship could be established for g_s and leaf ABA concentration across the WUE_i groups. Similarly, a common non-linear relationship between leaf ABA concentration and soil water potential was found. The latter findings suggest that the investigated population did not harbour significant genetic variation as to ABA production as function of soil desiccation level or with respect to the sensitivity of stomatal aperture vis-à-vis leaf ABA concentration and soil water potential.     

不同覆盖度下盆栽小白菜蒸散与水分利用效率

通过盆栽试验,研究了不同覆盖度条件下小白菜所处小环境的温湿度动态,以及作物蒸腾和盆栽基质蒸发的耗水规律。结果表明：植株生长点的温湿度随覆盖度的增大而增加。昼夜蒸散量随覆盖度的增大而减小,白天蒸散量变化显著,无覆盖处理白天蒸散量为最大,1/2圆覆盖处理仅次于无覆盖处理,15/16圆覆盖处理最小。小白菜从出苗到收获总的耗水量随覆盖度增大而减小,1/2圆覆盖、3/4圆覆盖、15/16圆覆盖处理的总耗水量分别为无覆盖处理的91.34%、69.03%和40.74%。无覆盖、1/2圆覆盖、3/4圆覆盖、15/16圆覆盖处理的地上部干物质质量的平均值分别为5.551、6.536、5.143、3.345 g,其水分利用效率的平均值分别为1.53、1.97、2.05、2.25 kg/m3。试验总结表明盆栽小白菜的水分利用效率随着覆盖度的增加而增加,15/16圆覆盖处理最高。     

Nutrients uptake and water use efficiency of drip irrigated maize under deficit irrigation

Little is known about nutrient uptake during different growth stages of drip irrigated maize under deficit irrigation. A 2-year field study in the semi-arid region of Upper Egypt was carried out in a randomized complete block design with five replications during the summer of 2016 and 2017. Maize plants were irrigated with 100, 80, or 60% of water requirements. Maize growth was negatively affected by the lower water supply. Total uptake of nitrogen (N), phosphorus (P), and potassium (K) by maize irrigated with I₁₀₀ increased by 21, 25, and 21% compared to that irrigated with I₆₀. I₈₀ reduced the grain and straw yield by 8 and 17% compared to I₁₀₀. Under deficit irrigation water was used efficiently more than full water supply. NPK requirements of drip irrigated maize under deficit irrigation are less than those irrigated by full water supply thus help to sustain the environmental ecosystem and increased the economic returns.     

Interception and use efficiency of light in winter wheat under different nitrogen regimes

In an identical experiment conducted at Mandan (ND), Manhattan (KS) and Lubbock (TX), the influence of the environment and nitrogen (N) fertility upon light interception efficiency (ei) and light use efficiency (ec) of winter wheat (Triticum aestivum L.) were examined using remotely sensed canopy reflectance data to estimate ei. Treatments consisted of two cultivars, four levels of applied N and three levels of irrigation. Increased N application resulted in increased ei, with only secondary effects on ec. Whole season values of ec did not differ significantly between sites or between crops grown under different N regimes. However, ec did change through the season, increasing from an average of 1.5 during the double ridge-to-terminal spikelet stage to an average of 3.8 during the terminal spikelet-to-anthesis stage and finally decreasing to an average of 3.1 during the anthesis-to-soft dough stage. These changes in ec corresponded to changes in the mean temperatures for each growth period.     

控制灌溉水稻叶片水平的水分利用效率试验研究

根据现场试验资料,分析了晚稻叶片水平的水分利用效率的日变化与全生育期变化,叶片的水分利用效率与气孔导度及外界影响因子包括光合有效辐射、土壤水分、叶气温差等的相互关系。结果表明：控制灌溉水稻叶片的水分利用效率在较高土壤水分时与对照处理差别不明显,适度土壤水分调控可以获得较高的水分利用效率;全生育期水稻叶片的水分利用效率随土壤水分变化而波动,过高过低的土壤水分均不利于水分利用效率的提高;叶片的光合速率、蒸腾速率与水分利用效率均随气孔导度的增加表现出先增后减的变化规律。水稻叶片的水分利用效率影响因素分析显示：水分利用效率随叶气温差、二氧化碳浓度和空气湿度的增加而增加;有利于获得较高水分利用效率的气孔导度、光合有效辐射、空气温度和土壤水分范围分别是200～350 μmol·m^-2·s^-1、400～900 μmol·m^-2·s^-1、28～34℃和85%～90%的土壤饱和含水率。     

A decision-support model for monitoring nutrient balances under agricultural land use (NUTMON)

A quantitative model of the balance between inputs and outputs of nitrogen, phosphorus and potassium in African land use systems (NUTBAL) was recently developed at two scales: supra-national (38 sub-Saharan African countries) and regional (Kisii District, Kenya). Calculating inputs (mineral fertilizer, organic manure, wet and dry deposition, biological nitrogen fixation, sedimentation) and outputs (removal of above-ground crop parts, leaching, denitrification, water erosion) led to the conclusion that there are considerable net fertility losses in each growing period.

In this paper, NUTBAL is elaborated into a decision-support model (NUTMON) to monitor the effects of changing land use, and suggest interventions that improve the nutrient balance. As input and output determinants cannot all be quantified equally well, the model recognizes primary data, estimates, and assumptions. The NUTMON determinants are mostly scale-neutral and can therefore be used to monitor nutrient balances at farm, regional, national and supra-national level. This is essential since the hierarchical levels interact. A number of recent interventions at the regional level (Kisii District, Kenya) are elaborated, including national fertilizer and produce price policies, fertilizer supply in small packages, zero-grazing, agroforestry, soil conservation measures, and increasing fertilizer use efficiency. It is shown that a major nutrient conservation effort in Kisii reduces nutrient depletion by approximately 50%, but does not entirely redress the N and K balance. To achieve the latter without reducing crop production, 75% of the district would have to be converted to a rotation system of maize and green manure cover crops, whereas 25% can remain under tea.

NUTMON has the potential to become a dynamic tool for land use policies, geared towards a balanced nutrient status in African land use systems. It can assist decision makers in determining the effects of current and alternative land use scenarios, taking account of both the productivity as well as the long-term sustainability of agro-ecosystems.