Changes in Soil Properties in Response to Irrigation of Potato by Urban Wastewater

This study evaluated the physicochemical changes in the soil of potato field that was irrigated by fresh water, differentially diluted wastewater and undiluted wastewater (hereafter called wastewater). The potato crop was cultivated for consecutive three seasons under fertilized and unfertilized conditions. The wastewater contained higher concentrations of organic carbon (C), nitrogen (N), phosphorus (P), potassium (K), sodium (Na), calcium (Ca), magnesium (Mg), sulfur (S), zinc (Zn) and boron (B) and lower concentrations of heavy metals. In this study, properties of wastewater-irrigated soil were compared with fresh water-irrigated soil. The application of wastewater reduced the bulk density of the surface soil by 2.83% and augmented the porosity by 6.02%. The unsaturated hydraulic conductivity and water retention capacity of the soil were improved under wastewater irrigation. Soil pH increased due to wastewater application but decreased, to a smaller extent, due to fertilizer application. Soil EC increased both with wastewater and fertilizer application; both parameters changed significantly in the top 0–15 cm soil layer. But, at the deeper layers, they were not affected by wastewater application. The organic C, total N, available P and S of the soils increased significantly (p = 0.05) when potato field was irrigated with raw wastewater. The organic C increased by 23.80% under wastewater irrigation in the top soil layer. The N content of the soil showed similarities with the organic C contents. Exchangeable Na, K, Ca, Mg; Zn and B of the soil also increased significantly with wastewater application. So, irrigation with urban wastewater is suggested to improve soil fertility as well as to ease pressure on the fresh water in the area of water scarcity.     

养殖废水灌溉下施用生物质炭和果胶对土壤养分和重金属迁移的影响

【目的】 养殖废水中含有丰富的养分,但也含有一定的重金属。本文研究了生物质炭和果胶对养殖废水灌溉下的土壤–植物系统养分和重金属迁移规律的影响,以利用养殖废水中的养分,并对其重金属进行调控。 【方法】 选取新乡市郊区农田土壤为供试土壤,采用根箱试验方法种植玉米。设置根箱土壤中添加1%的生物质炭和果胶,分别灌溉蒸馏水和养殖废水发酵产生的沼液。测定了土壤中养分和重金属的含量,探讨了其在土壤–植物系统的迁移规律。 【结果】 沼液灌溉的植株地上部生长与蒸馏水灌溉无显著差异。果胶相比于生物质炭可以促进植株生长。沼液灌溉时,果胶处理的根系和地上部生物量分别比对照增加了25.38%和31.21%。沼液灌溉普遍降低了根际和非根际土壤的pH,生物质炭处理和果胶处理与对照根际和非根际土壤的pH均无显著差异。沼液灌溉增加了非根际土壤的电导,生物质炭相比于果胶增加了土壤的电导。沼液灌溉增加了土壤全氮、有效磷、速效钾和有机质含量。果胶根际土壤的全磷、碱解氮、有效磷、有效Fe、有效Mn均高于生物质炭处理,生物质炭处理根际和非根际土壤的全钾和速效钾含量均高于果胶处理。沼液灌溉相比于蒸馏水灌溉,增加了植株根、茎中N含量和Ca含量。生物质炭处理植株根茎叶N含量、根茎P含量、茎K含量、根茎叶Ca含量、根茎Mg含量高于果胶处理,但果胶处理养分的转运系数较高。养殖废水灌溉增加了根际和非根际土壤中有效Cu和Zn尤其是Zn的含量。与对照相比,生物质炭降低了根际土壤Cu、Pb、Ni的含量,而果胶增加了它们的含量。沼液灌溉增加了植株根茎叶中Cu、Zn、Pb含量,果胶处理植株根系Cu、Zn、Pb、Cd、Ni含量最高,但向地上部转运较少。 【结论】 在北方碱性土壤灌溉养殖废水发酵产生的沼液时,施用生物质炭和果胶可以提高土壤肥力和植株养分含量,生物质炭通过减少土壤中有效态重金属含量以减少重金属在植物体内累积,果胶虽然增加土壤有效态重金属含量,但可以降低其向地上部的转运,避免了重金属在植物体内的累积。      

部分根区干燥灌溉条件下土壤温度和玉米N吸收改善研究

Soil temperature is a major effective factor on the soil and plant biological properties. Irrigation can affect soil temperature and thereby induces a temperature effect on plant growth, which may result in an economic increase due to higher yield and plant nutrition. A field experiment was carried out to investigate the effects of three irrigation strategies including full irrigation (FI), partial root-zone drying (PRD) and deficit irrigation (DI) on soil temperature and the consequent results on the grain yield and N uptake of maize (Zea May L.). Soil temperature was measured by time domain reflectometry (TDR) sensors during the 2010 growing season. Irrigation treatments were applied from 55 to 107 d after planting. The PRD treatment caused soil temperature to be in a favorable domain for a longer period (for over 60% of the measuring dates) as a consequent result of water movement to deeper soil layers compared with the other treatments; the PRD treatment also reduced soil temperature at deeper soil depths to below the maximum favorable soil temperature for maize root growth, which resulted in deeper root penetration due to both water availability and favorable soil temperature. Compared to the FI treatment, the PRD treatment increased root water uptake by 50% and caused no significant reduction in total N uptake, while this was not observed in the DI treatment partially due to the negative temperature effect of DI on plant growth, which consequently affected the water and nutrient uptake. A longer vegetation period in the PRD treatment was observed due to higher leaf N concentrations and no significant reduction in maize grain yield occurred in the PRD treatment, compared with those in the FI treatment. Based on the results, having 15.2% water saving during the whole growing season, the PRD irrigation would positively affect soil temperature and the water and nutrient uptake as a consequent, which thereby would prevent significant reduction in maize grain yield.     

Treated municipal wastewater for citrus irrigation 1

Treated, reclaimed municipal wastewater was evaluated on citrus trees in central Florida for over six years. The effects of irrigation with reclaimed wastewater on soil water content, soil chemical analysis, leaf mineral status, and fruit quality were compared with those of irrigation with well water. Irrigation with reclaimed water increased mineral residues in the soil profile, altered leaf mineral concentration and fruit quality, and promoted better tree performance and more weed growth relative to irrigation with well water. Higher accumulation of nitrogen (N), potassium (K), calcium (Ca), and magnesium (Mg) in soils irrigated with reclaimed water were not significantly reflected in leaf mineral status. Although leaf sodium (Na), chloride (Cl), and boron (B) concentrations were noticeably higher in reclaimed water treatments than in those of well water, they are still far below the toxicity levels. This highly treated wastewater in central Florida has been found to be a very safe and good option for increasing water supplies, but not a significant source of plant nutrients to citrus trees.     

Effects of wastewater irrigation on soil and cabbage‐plant (brassica olerecea var. capitate cv. yalova‐1) chemical properties

The use of wastewater for irrigation is increasingly being considered as a technical solution to minimize soil degradation and to restore nutrient contents of soils. The aim of this study is to increase fertility and minimize degradation of soils irrigated with wastewater exposed to different purification treatments. A field experiment was conducted to investigate the effects of control and irrigation with wastewater, which had undergone different purification treatments, on macro‐ and micronutrient distribution within the soil profile and nutrient contents of cabbage (Brassica olerecea var. Capitate cv. Yalova‐1) in Erzurum, Turkey. Wastewater irrigation and preliminary treatment–wastewater irrigation significantly affected soil chemical properties especially at 0–30 cm soil depth and plant nutrient contents after one year. Application of wastewater increased soil salinity, organic matter, exchangeable Na, K, Ca, Mg, plant‐available P, and micro‐elements and decreased soil pH. Wastewater increased also yield and N, P, K, Fe, Mn, Zn, Cu, B, and Mo contents of cabbage plants. Undesirable side effects were not observed in plant heavy‐metal contents, due to salinity and toxic concentrations of metals from the application of wastewater to soil.     

Physicochemical Properties of Soil under Wheat Cultivation by Irrigation with Municipal Wastewater in Bangladesh

Irrigation with wastewater provides the opportunity to solve the problems of its disposal, reuse and water conservation. Freshwater, differentially diluted wastewater and undiluted wastewater (hereafter called wastewater) were used to grow wheat in sandy loam soil under fertilized and unfertilized conditions at the experimental farm of Bangladesh Agricultural University, Bangladesh. Fresh groundwater and wastewater of Mymensingh municipality were used to irrigate a wheat field for three consecutive years to examine the effects of wastewater application on soil properties. In this study, the properties of wastewater-irrigated soil were compared with freshwater-irrigated soil. The application of wastewater reduced the bulk density of the surface soil by 1.92% and augmented the porosity by 5.89%. The unsaturated hydraulic conductivity and water retention capacity of the soil were improved under wastewater irrigation. Soil pH increased due to wastewater application but decreased, to a smaller extent, due to fertilizer application. Soil electrical conductivity (EC) increased both with wastewater and with fertilizer application; both parameters changed significantly in the 0–20 cm soil layer. However, at the deeper layers, they were not affected by wastewater application. The organic carbon (C) and total nitrogen (N) level of the soils were higher under wastewater irrigation than under freshwater-irrigated soil. The organic C increased by 23.93% under wastewater irrigation in the top 20 cm soil layer. The N content of the soil showed similarities with the organic C contents. Available P and S concentrations were greater in the soil irrigated with wastewater compared with the soil irrigated with freshwater. The exchangeable cations – sodium (Na), potassium (K), calcium (Ca) and magnesium (Mg) – also increased significantly with wastewater application. Thus, farmers are advised for irrigation with municipal wastewater to ease pressure on freshwater and to improve soil fertility.     

华北平原冬小麦对过去30年气候变化响应的敏感性研究

以气候变暖为主要特征的全球变化已经对人类的生产和生活产生重要影响。作物物候及产量对气候变化的响应和适应是研究气候变化对农业生产影响的重要内容。本文选择位于华北平原的4个典型农业气象试验站(唐山、惠民、商丘和驻马店),利用详细的物候和产量观测资料,在站点尺度上研究了冬小麦物候及产量对过去30年(1980—2009)气候变化的响应及其敏感性。结果表明:过去30年冬小麦出苗期推迟,而抽穗期和成熟期呈提前趋势。物候期的提前或推迟导致冬小麦不同生长发育阶段历时发生变化,出苗—抽穗阶段(营养生长阶段)呈缩短趋势,而抽穗—成熟生长阶段(生殖生长阶段)呈延长趋势。相关性研究表明:在4个研究站点,温度和辐射是制约冬小麦产量的主要气候因子;但不同生长阶段,冬小麦产量对气象因子的响应不同。利用多元回归统计方法研究冬小麦产量对不同生长阶段气候因子(温度、辐射和降雨)的敏感性发现:在出苗—抽穗生长阶段,除驻马店站点外,温度升高对冬小麦产量有正效应;而在抽穗—成熟阶段,温度升高会给产量带来负面影响。冬小麦产量与辐射呈正相关,辐射降低给冬小麦产量产生负效应。     

废水灌溉下有机物料对重度盐渍土养分及芦苇生长的影响

在山东滨州含盐量为16.7 g.kg 1的重度退化滨海盐碱湿地,研究了造纸废水灌溉条件下添加有机物料对盐渍土养分和芦苇生长的影响,以期为重度退化滨海盐碱湿地的生物修复提供依据。试验从春季开始进行,共设4种处理:翻耕对照(CK)、翻耕+废水灌溉(FF)、翻耕+废水灌溉+秸秆(FFJ)以及翻耕+废水灌溉+污泥(FFW),测定了不同处理下土壤养分、呼吸强度、含盐量及芦苇株高和生物量的变化。结果表明,与对照相比,各处理土壤有机质显著提高,10月末时FFJ、FFW和FF处理土壤有机质含量分别是对照的1.34倍、1.29倍和1.22倍;碱解氮和有效磷含量也高于对照,依次为FFW>FFJ>FF>CK;各处理土壤呼吸强度高于对照,其中FFJ处理显著高于对照,比试验初期提高96%;各处理表层土壤含盐量均出现不同程度降低,以FFJ和FFW降低幅度最大,分别比对照降低22.6%和16.3%;FFW、FFJ和FF处理的芦苇株高显著高于对照,8月末分别是对照的3.1倍、2.7倍和2.2倍;FFJ和FFW处理的芦苇生物量、根冠比和平均叶面积都显著高于对照,而FF处理与对照没有显著差异;FF处理芦苇株高、生物量与土壤有效氮含量相关最为显著,FFJ和FFW处理与土壤有机质含量相关性最为显著。结果表明,废水灌溉为重度盐渍化土壤提供了充足的水分,有机物料能有效提高土壤养分含量,解决了重度盐碱化土壤水分胁迫和养分胁迫的问题,促进芦苇生长,但秸秆和污泥两种有机物料之间没有显著差异。     

Impact of Treated Industrial Effluent on Physical and Chemical Properties of Three Subtropical Soils and Millet Nutrition

The use of treated industrial effluents to irrigate plants is an alternative, because of nutrients that can increase yield of the agricultural crops. This study was conducted to determine irrigation with treated effluent and gypsum application, which changes the chemical and physical characteristics of soils and the growth and nutrition of millet (Pennisetum glaucum). Thus, an experiment was conducted on PVC columns with three soil classes, Typic Hapludox, Typic Hapludult, and Arenic Hapludult. Nutrient and Na⁺ concentrations in the millet biomass reflected concentrations of elements in the effluent and soil. In the control, low N levels were found in the biomass, while higher leaf N concentrations were observed, due to irrigation with treated effluent. In the short term, irrigation with treated industrial effluent by controlled application could be an alternative and a complementary source of nutrients for plants, reducing the volume of nutrients and organic materials discharged into water bodies.     

水肥耦合对玉米化学计量学特征及其生长性状的影响

为了探讨不同水肥条件下玉米C、N、P化学计量学特征及其影响因素,设置土壤不同含水量和全氮含量的盆栽试验,分析了不同水肥对玉米生长性状和碳氮磷化学计量学特征的影响,并对两者进行了相关分析。试验设置田间持水量的90%,70%,50%(W1、W2、W3),田间正常施氮量的150%,100%,50%,(N1、N2、N3),共9个处理。结果表明:玉米根、茎、叶不同器官干物质量均随着施氮量的减少而减少,随着土壤含水量的增加而增加。高、中水分时玉米株高随着施氮量的增加而增加,当玉米处于干旱胁迫时施氮量对玉米株高影响不大。低水分下的茎粗显著低于高、中水分。玉米根、茎、叶的C含量差异不显著。低氮施肥处理下玉米根、茎和叶的N含量均显著低于中、高氮处理,而后两者对根、茎和叶的N含量的影响表现不一,其中对茎氮含量差异达到显著水平,对叶氮含量在抽雄期以后才显著。玉米C∶N∶P生态化学计量特征随水肥因素的变化表现不一,其中N/P平均为6.01,随着施氮量的增加而升高,随土壤含水量的增加而降低;C/N为0.31,随着施氮量的增加而降低,对水分因素不敏感;C/P为1.62,表现出强烈的内稳性,不随外界生物与非生物环境的变化而变化。     

An evaluation and comparison of drip and conventional furrow irrigation methods on maize

A field study was conducted over two years on maize at Islam Abad Research Station at 34°7′42′′N and 46°27′23′′E and elevation of 1348 m a.s.l in Kermanshah Province, western Iran in order to compare the effects of different irrigation methods and treatments on irrigation water use efficiency, crop yield, yield response factor, pan and seasonal crop coefficients, and other maize parameters. The experiment was a complete randomized block design with three replicates. During the study, irrigation water was applied at 40, 60, 80 and 100% of the maize seasonal water requirement for different surface drip tape (SDT) treatments, and 100% only for conventional furrow irrigation treatments with and without soil and water monitoring. The results showed that by using the above-mentioned different drip tape and surface treatments with soil and water monitoring, maize seasonal irrigation water use savings of 81, 71, 61, 52 and 36% were achieved compared with local conventional furrow irrigation without any soil, water and root monitoring, respectively. The yield response factor (K _y), seasonal crop (K _c) and pan coefficient (K _p) for maize were 0.80, 0.76 and 0.97, respectively.     

长期定位试验中氮肥与磷肥有机肥联合施用通过刺激根的生长增加玉米产量和养分吸收

Imbalanced application of nitrogen (N) and phosphorus (P) fertilizers can result in reduced crop yield, low nutrient use efficiency, and high loss of nutrients and soil nitrate nitrogen (NO₃^--N) accumulation decreases when N is applied with P and/or manure; however, the effect of applications of N with P and/or manure on root growth and distribution in the soil profile is not fully understood. The aim of this study was to investigate the combined effects of different N and P fertilizer application rates with or without manure on maize (Zea mays L.) yield, N uptake, root growth, apparent N surplus, Olsen-P concentration, and mineral N (Nmin) accumulation in a fluvo-aquic calcareous soil from a long-term (28-year) experiment. The experiment comprised twelve combinations of chemical N and P fertilizers, either with or without chicken manure, as treatments in four replicates. The yield of maize grain was 82% higher, the N uptake 100% higher, and the Nmin accumulation 39% lower in the treatments with combined N and P in comparison to N fertilizer only. The maize root length density in the 30--60 cm layer was three times greater in the treatments with N and P fertilizers than with N fertilizer only. Manure addition increased maize yield by 50% and N uptake by 43%, and reduced Nmin (mostly NO₃^--N) accumulation in the soil by 46%. The long-term application of manure and P fertilizer resulted in significant increases in soil Olsen-P concentration when no N fertilizer was applied. Manure application reduced the apparent N surplus for all treatments. These results suggest that combined N and P fertilizer applications could enhance maize grain yield and nutrient uptake via stimulating root growth, leading to reduced accumulation of potentially leachable NO₃^--N in soil, and manure application was a practical way to improve degraded soils in China and the rest of the world.     

Dynamics of maize (Zea mays L.) leaf straw mineralization as affected by the presence of soil and the availability of nitrogen

An incubation experiment was carried out with maize (Zea mays L.) leaf straw to analyze the effects of mixing the residues with soil and N amendment on the decomposition process. In order to distinguish between soil effects and nitrogen effects for both the phyllospheric microorganisms already present on the surface of maize straw and soil microorganisms the N amendment was applied in two different placements: directly to the straw or to the soil. The experiment was performed in dynamic, automated microcosms for 22 days at 15 °C with 7 treatments: (1) untreated soil, (2) non-amended maize leaf straw without soil, (3) N amended maize leaf straw without soil, (4) soil mixed with maize leaf straw, (5) N amended soil, (6) N amended soil mixed with maize leaf straw, and (7) soil mixed with N amended maize leaf straw. ¹⁵NH₄¹⁵NO₃ (5 at%) was added. Gas emissions (CO₂, ¹³CO₂ and N₂O) were continuously recorded throughout the experiment. Microbial biomass C, biomass N, ergosterol, δ¹³C of soil organic C and of microbial biomass C as well as ¹⁵N in soil total N, mineral N and microbial biomass N were determined in soil samples at the end of the incubation. The CO₂ evolution rate showed a lag-phase of two days in the non-amended maize leaf straw treatment without soil, which was completely eliminated when mineral N was added. The addition of N generally increased the CO₂ evolution rate during the initial stages of maize leaf straw decomposition, but not the cumulative CO₂ production. The presence of soil caused roughly a 50% increase in cumulative CO₂ production within 22 days in the maize straw treatments due to a slower decrease of CO₂ evolution after the initial activity peak. Since there are no limitations of water or N, we suggest that soil provides a microbial community ensuring an effective succession of straw decomposing microorganisms. In the treatments where maize and soil was mixed, 75% of microbial biomass C was derived from maize. We concluded that this high contribution of maize using microbiota indicates a strong influence of organisms of phyllospheric origin to the microbial community in the soil after plant residues enter the soil.     

城市污水再生水灌溉对黑麦草生长及土壤磷素转化的影响

为了进一步明确城市污水再生水的农业利用价值,在温室条件下采用盆栽试验方法种植黑麦草,以自来水(clean water,CW)灌溉为对照,分别进行全再生水(reclaimed municipal wastewater,RW)和混合再生水(自来水+再生水,CW+RW,1∶1)灌溉处理,研究了再生水灌溉对黑麦草生长和土壤磷素的转化特征。结果表明,城市污水再生水灌溉显著增加了黑麦草地上部和根系的生物量,CW+RW处理黑麦草地上部和根系生物量在播种55 d后分别较对照(CW)增加18.92%和6.42%,RW处理分别增加26.79%和10.55%;黑麦草地上部磷含量分别显著增加8.48%和10.93%。再生水灌溉土壤全磷含量变化不大并有减少趋势,但土壤速效磷含量CW+RW和RW处理分别较对照(CW)增加29.15%和43.80%;CW+RW和RW处理显著增加了土壤有机磷组分中的活性有机磷和中活性有机磷,与对照CW相比,其中活性有机磷增幅分别为50.30%和81.57%,中活性有机磷增幅分别为7.66%和13.68%;也显著增加了无机磷组分中的Ca2-P和Ca8-P,CW+RW和RW处理Ca2-P含量由对照的12.90 mg·kg-1分别增加到16.42 mg·kg-1和15.49 mg·kg-1,与对照相比,增幅分别为27.29%和19.38%,Ca8-P增幅分别为19.94%和16.03%。再生水灌溉显著降低了土壤pH并显著增加了土壤有机质含量,这可能是增加土壤磷活性的原因之一。再生水灌溉对提高土壤磷素利用率有促进作用。     

施肥对淡灰钙土春玉米产量和土壤水盐运移的影响

在宁夏灌区淡灰钙土上,通过田间试验的方法,研究了喷灌和漫灌条件下不同氮磷钾施用量对春玉米产量和土壤水盐运移动态的影响。结果表明:不同施肥处理的平均产量为6.9～13.2 t/hm²,变异系数为2.7%～13.6%。相对于对照处理,不同氮磷钾配比都能显著提高产量（不施氮肥处理除外,P < 0.05）,增产率为12.7%～92.5%。氮磷钾施用量与春玉米产量都服从二次曲线关系,增产效应为氮肥 > 钾肥 > 磷肥。在玉米生育期内,喷灌更有利于0—20 cm和20—50 cm土层土壤水分分布的均匀性,而漫灌造成土壤水分向深层50—80 cm运移。在喷灌条件下,土壤盐分通常表聚在0—20 cm土层,其最高含量可达2.11 g/kg,而漫灌使盐分向深层土壤运移,50—80 cm土层盐分含量达0.53～1.07 g/kg。因此,在淡灰钙土春玉米种植条件下,喷灌配合氮磷钾施肥可显著增产,但其对耕层土壤的洗盐效果不及漫灌施肥。     

TREATED EFFLUENT AND SALINE WATER IRRIGATION INFLUENCES SOIL PROPERTIES,YIELD, WATER PRODUCTIVITY AND SODIUM CONTENT OF SNOW PEAS AND CELERY

To determine the effects of irrigation water quality, plants were irrigated with normal potable water [0.25 dS m^?1 electrical conductivity (EC), 25 mg L^?1 sodium (Na), 55 mg L^?1 chloride (Cl)], treated effluent (0.94 dS m^?1 EC, 122 mg L^?1 Na, 143 mg L^?1 Cl) and saline water with low salinity (1.24 dS m^?1 EC, 144 mg L^?1 Na and 358 mg L^?1 Cl) and high salinity (2.19 dS m^?1 EC, 264 mg L ^?1Na and 662 mg L^?1 Cl) for snow peas, and high salinity (3.07 dS m^?1 EC, 383 mg L^?1 Na and 965 mg L^?1 Cl) and very high salinity (5.83 dS m^?1 EC, 741 mg L^?1 Na and 1876 mg L^?1 Cl) for celery. The greater salts build up in the soil and ion toxicity (Cl and Na) with saline water irrigation contributed to significantly greater reduction in root and shoot biomass, water use, yield and water productivity (yield kg kL^?1 of water used) of snow peas and celery compared with treated effluent and potable water irrigation. There was 8%, 56% and 74% reduction in celery yield respectively with treated effluent, high salinity and very high salinity saline water irrigation compared with potable water irrigation. The Na concentration in snow peas shoots increased by 54%, 234% and 501% with treated effluent, low and high salinity saline water irrigation. Similarly, the increases in Na concentration in celery shoots were 19%, 35% and 82%. The treated effluent irrigation also resulted in a significant increase in soil EC, nitrogen (N) and phosphorus (P) content compared with potable water irrigation. The heavy metals besides salts build up appears to have contributed to yield reductions with treated effluent irrigation. The study reveals strong implications for the use of saline water and treated effluent for irrigation of snow peas and celery. The salt build up within the root zone and soil environment would be critical in the long-run with the use of saline water and treated effluent for irrigation of crops. To minimize the salinity level in rhizosphere, an alternate irrigation of potable water with treated effluent or low salinity level water may be better option.     

Influence of Nitrogen and Saline Water on the Growth and Partitioning of Mineral Content in Maize

ABSTRACT

Saline irrigation water has a tremendous impact on the yield potential of crops. Distribution of mineral elements in the parts of maize plant in response to saline water and nitrogen (N) nutrition was studied in a pot experiment for six weeks. Plants were irrigated either with tap water or saline water (ECw: 3.2 dSm^?1). Nitrogen was applied at the rate of 0, 50, 100 and 200-kg ha^?1 denoted as N0, N1, N2, and N3, respectively. Plants were separated into leaf, stem and root and analyzed for N, calcium (Ca), magnesium (Mg), sodium (Na), and potassium (K) concentrations. Dry matter production of leaf, stem and root was significantly reduced with saline water. The partitioning of elements in plants was the function of nitrogen and saline water. The N concentration of plant parts varied in the order of leaf > stem > root. A significant decrease in the N content was noted in plants under saline water. The root contained the highest Na content, Ca and Mg were higher in the leaf, whereas K was highest in the stem under saline water. Sodium was highest in the root and the remainder elements were greatest in the stem under tap water. Potassium and Cl were significantly reduced by N level whereas the reverse was true for Ca, Mg and Na content. The Na/K, Na/Ca, and Na/Mg ratios were also higher in salt stressed plant parts due to higher accumulation of Na ion. Among N-fertilizer treatments the Na/Ca and Na/Mg ratios were highest in control whereas Na/K increased with the addition of N. This study indicated that interaction of saline water and nitrogen has mixed effects on the partitioning of mineral elements in maize.     

分根区交替灌溉对玉米水分利用和土壤微生物量碳的影响

分根区交替灌溉由于创造了一个土壤水分分布不均匀的环境,从而影响土壤中微生物活性,作物水分和养分利用。为探明这种影响,该文通过盆栽试验,研究了在2种灌水水平(正常灌水W1,70%～80%田间持水率;轻度缺水W2,60%～70%田间持水率)和2种有机无机氮比例(100%无机氮,70%无机氮+30%有机氮)条件下,常规灌溉和不同生育期分根区交替灌溉(分别在苗期～灌浆初期、苗期～拔节期以及拔节期～抽雄期进行分根区交替灌溉(AI),即AI1、AI2和AI3)对玉米干物质积累、水分利用以及拔节期、抽雄期和灌浆初期土壤微生物量碳(MBC),可溶性碳(DOC)含量以及基础呼吸和诱导呼吸CO2释放量等的影响。结果表明,与常规灌溉相比,轻度缺水时,拔节期～抽雄期分根区交替灌溉总干物质质量增加23.2%～27.4%,水分利用效率提高23.3%～26.7%;相同施肥和灌水水平条件下,抽雄期时拔节期～抽雄期分根区交替灌溉土壤MBC增加,但是土壤诱导呼吸CO2释放量降低。与单施无机氮相比,有机、无机氮配施增加玉米干物质质量,在某些水分条件下(W1CI、W1AI1和W1AI2)还提高灌浆初期基础呼吸和诱导呼吸CO2释放量。因此,轻度缺水时拔节期～抽雄期进行分根区交替灌溉可以提高玉米总干物质质量、水分利用效率和微生物量碳。     

再生水灌溉对玉米和大豆品质影响的试验研究

为了合理利用城市污水处理后的再生水资源，研究再生水灌溉对作物品质的影响，该文采用北京高碑店污水处理厂的两种再生水(二级再生水、三级再生水)，以清水为对照进行玉米和大豆盆栽种植试验。通过对籽粒常规养分、微量元素和重金属含量等项目的测定分析，对再生水灌溉情况下的作物品质进行研究。研究结果表明：再生水灌溉对玉米和大豆籽粒粗蛋白、粗淀粉含量无显著影响；在微量元素方面，对大豆籽粒的影响同对照差异不显著，而对玉米籽粒的影响同水质有关；玉米和大豆籽粒中的重金属铅、镉含量虽均低于国家卫生标准(GB 2715-1981)规定，但二级再生水灌溉的玉米镉含量相对对照增加显著。因此认为三级再生水相对二级再生水应用于作物灌溉更具安全性，对二级再生水中重金属镉含量应严格控制。     

Influence of Quercus ilex trees on herbaceous production and nutrient concentrations in southern PortugalElena Cubera1, 2

In an open woodland in Portugal, the nature of interactions between Quercus ilex trees and herbaceous plants was assessed during 2 years by studying how manipulation of incident solar radiation, water and nutrient supply affect the herbaceous biomass and N, K, P, Ca, Mg, and Mn concentrations. Measurements were carried out in three environments consisting of (1) open grassland, (2) beneath the tree canopy, and (3) under artificial shade. Each of these environments was subjected to two regimes of fertilization and two water levels in a factorial design. The fertilizer treatment consisted of application of no fertilizer or a combination of 200 kg calcium ammonium nitrate ha^–1 (26% N) and 350 kg superphosphate ha^–1 (8% P), while the water‐supply treatment consisted of either no irrigation or irrigation fortnightly from February 1 to April 30. Grasses showed significantly lower nutrient concentrations than forbs. However, nutrient concentrations of the whole herbaceous community were within the recommended ranges for cattle nutrition. A negative effect of shade on herbaceous biomass production was observed. The effect of watering on herbaceous biomass was less prominent than the effect of fertilization, irrespective of the environment, suggesting that Q. ilex does not compete for soil‐water resources with herbaceous biomass in this ecosystem. Fertilization increased total biomass by 106%, 49%, and 97% in the open grassland, beneath the tree canopy, and under artificial shade, respectively. During the first and second year, fertilization increased herbaceous P concentrations by 24% and 83%, respectively, if compared with concentrations obtained at the unfertilized plots. Higher K and Mg concentrations were observed in herbaceous plants beneath the tree canopy than in the open areas, indicating a positive effect of trees on pasture quality. The positive and negative effects of trees on understory forage are discussed.