Wastewater Irrigation Effect on Soil,Crop and Environment: a Pilot Scale Study at Irbid,Jordan

An investigation was carried out at pilot scale to test the feasibility of using the effluent of a rotating biological contactors (RBC) unit treating wastewater generated from a university campus. The objective of the study was to cerefully monitor the impact of wastewater irrigation on the soil, percolating water, crop growth and the pathogenic condition within the immediate vicinity of wastewater application. Experimental plots with three crops: alfalfa, radish and tomato were irrigated with fresh and waste waters. The irrigation water was applied by sprinklers. Each crop was given two sub-treatments: with fertilizer and without fertilizer. The physical and chemical properties of the soil, the crop yields, and subsurface drainage were measured. In most of the cases, the yields resulted from the uses of wastewater with fertilizer were compatible with those of the uses of freshwater with fertilizer. The washings of tomato fruits grown with wastewater were analyzed for fecal coliforms. It appeared that the fruit skins were free of viable fecal coliforms 24 hours after the wastewater application. Subsurface drainage analyses did not show any alarming levels of constituents irrespective of the source of the water: wastewater or freshwater. The wastewater irrigation applied for a season had no significant effect on a silty loam soil. With wastewater irrigation, slught changes in the soil porosity and salinity were observed.     

微咸水喷灌对作物影响的研究进展

微咸水喷灌条件下, 作物同时受到土壤盐分和喷灌水盐分的双重影响。大部分作物通过叶片吸收盐分的速率与盐分浓度和喷水历时基本上呈线性函数关系; 同时, 喷灌过程中不仅要监测灌溉水的电导率, 而且与其他水源混合时也要监测离子组成, 尽量降低Mg²⁺、Cl^-和Na⁺的含量。喷灌频率的增加比喷水历时的增加更能增加作物盐分的吸收, 并加重对作物的损伤。微咸水喷灌后短时间的淡水冲洗可以减少作物叶片对盐分的吸收。微咸水喷灌显著降低成熟植被的生物量和作物累积耗水量, 造成作物一定程度的减产, 而且具有累积效应; 但作物产量和叶片汁液离子浓度没有明显的相关关系。今后, 应重点研究以下5个方面的问题: (1)微咸水喷灌下作物的耐盐性评价指标, 建立相应的评价体系; (2)选育耐微咸水喷灌的品种, 尤其是用于草场恢复重建、城市绿化、盐渍土改良等耐盐牧草、草坪草的选育; (3)制定与微咸水喷灌相适应的灌溉制度, 研究微咸水喷灌条件下作物叶片上和土壤中盐分的淋洗对微咸水喷灌具有重要的作用; (4)微咸水喷灌对作物影响的区域性和时效性, 应建立微咸水喷灌对作物产量影响的区域性评价和研究长期微咸水喷灌对作物的影响; (5)微咸水喷灌对土壤盐分积累及分布的影响。     

Micronutrients Losses from Soil under Subsurface Drainage System

The drainage system, although it reclaims waterlogged soils, poses a potential threat to leaching of valuable nutrients. To assess the micronutrient losses from such system established more than two decades ago in the plains of northwestern Pakistan, drainage waters were periodically analyzed for selected micronutrients. The inputs of micronutrients in irrigation waters were also determined. The micronutrient removal in drainage water was 1.39 to 9.79 times greater than micronutrient inputs in irrigation waters and fertilizers. Among micronutrients, the removal of copper (Cu) and manganese (Mn) in drainage water was greater than iron (Fe) and zinc (Zn). The concentrations of micronutrients generally changed with cropping (sampling time), increased with soil depth, and were invariably negative on the nutrient balance sheet, suggesting that these nutrients are continuously depleted from the system in drainage water. These nutrients therefore must be replenished in soil through an appropriate means for optimum crop yields under the given drainage–irrigation–cropping system.     

Soil Water,Fertility and Sustainable Agricultural Production in Arid and Semiarid Regions on the Loess Plateau*

Research by Academia Sinica shows that current crop production on the loess plateau is only slightly higher than one third of the potential. Soil water relationships and nutrient supply have been investigated and a long term (18 years) field experiment conducted. This work shows that the soil does have the capacity to support sustainable crop production and that higher yields are possible through appropriate fertilizer usage and irrigation. The fertility of loess‐derived soil is related to characteristics of the loess such as depth of the deposit, loose structure, water storage capacity and ammonium fixation capacity and its release to crops. On sloping land soil and water loss is significant; a prime requirement for the reduction of nutrient loss is the control of erosion. The two main factors limiting crop production are: drought stress and nitrogen deficiency. Covering the soil with plastic film or straw (or other crop residues) is effective in conserving soil moisture. Breeding of crop varieties more efficient in nutrient utilisation and more tolerant of drought stress can make a contribution to improvement of production.     

Direct and Residual Effects of Micronutrients on Crops in a Pattern in Floodplain Soil

ABSTRACT

Different micronutrients have variable residual effects in the soil. Again, crops have variability in their response to applied micronutrient. An experiment was conducted in floodplain soil of Bangladesh using cauliflower, maize, and rice in a pattern to explore differential effects of micronutrients on crops. Seven treatments following additive element trial technique including a control were used in the study. Micronutrients were applied @ 3 kg Zn, 2 kg B, 2 kg Cu, 3 kg Mn, 5 kg Fe and 1 kg Mo per hectare. Cauliflower as the first crop of the pattern responded to direct application of both zinc and boron whereas significant residual effects of these elements were observed in the second crop (maize). In rice as the third crop, no significant residual effects were estimated. In floodplain soil, zinc and boron fertilizers are needed to apply in each third crop of a pattern where the second crop is nutrient exhaustive like maize.     

Method development and application to determine potential plant uptake of antibiotics and other drugs in irrigated crop production systems

Studies have shown the detection of emerging contaminants (ECs), of which pharmaceuticals are a subset, in surface waters across the United States. The objective of this study was to develop methods, and apply them, to evaluate the potential for food chain transfer when EC-containing waters are used for crop irrigation. Greenhouse experiments were performed in which select food crops were irrigated with water spiked with three antibiotics. Field experiments, at two different sites, were conducted. Select crops were irrigated with wastewater effluent known to contain ECs, EC-free well water, and Colorado River water containing trace-level ECs. The results of the greenhouse studies show the potential for uptake of one or more of the antibiotics evaluated, albeit at very low levels. In those food crops watered with wastewater effluent, only an industrial flavoring agent, N,N'-dimethylphenethylamine (DMPEA), was consistently found. None of the evaluated contaminants were found in crops irrigated with Colorado River water.     

Effect of Municipal Wastewater as a Wetland Water Source on Soil Microbial Activity

Microbial activity levels of two soil materials, excavated from a wetland and irrigated with municipal wastewater effluent or Missouri River water, were compared. The wastewater had twice the electrical conductivity and four times the sodium concentration as river water. We performed activity assays on the soils before leaching, immediately after leaching, and after harvesting plants. Gas chromatography was used to measure carbon dioxide (CO₂) evolved in soil samples incubated for 7 d. Activity was significantly reduced in preleached wastewater–irrigated soils compared with river water–irrigated soils. Immediately after leaching, activity significantly increased and was similar to river water–irrigated soils. Activity decreased slightly after plant harvest in postleached treatments. Increased activity after leaching may be related to decreased salinity and sodicity, which probably lowered osmotic pressure in the soil. Our study demonstrated that soil salinity and sodicity induced by wastewater irrigation decreased microbial activity, which may impact nutrient cycling and glycophytic vegetation communities in wetlands.     

Treated Industrial Wastewater Effects on Chemical Constitution Maize Biomass,Physicochemical Soil Properties,and Economic Balance

Irrigation with treated wastewaters can improve nutrient levels and yield of crops planted on degraded soils. This study evaluated how irrigation with treated industrial wastewater affected biomass production and nutrition of maize plants and physio-chemical properties of a degraded soil. The experiment was conducted in a greenhouse using PVC columns. Treatments consisted of 8 treatments irrigated with clean water and increasing doses of N and P, and 8 treatments with 4 proportions of wastewater irrigation (25%, 50%, 75% and 100% v/v). In general, maize biomass did not differ between irrigation water sources. Differences were largely associated with N nutrition. We observed increases in concentrations of N, P, K, S, Mn, Na, Cu, and Zn in tissue of maize under irrigation with wastewater. The addition of treated wastewater increased the P and Na concentrations, and EC values in the soil without affecting clay dispersion in water. An associated economic analysis indicated that wastewater irrigation would not be economically feasible without including environmental benefits. In southern Brazil, the proportion of irrigation water that is wastewater should not exceed 50%.     

NUTRIENT UPTAKE AND USE EFFICIENCY BY TROPICAL LEGUME COVER CROPS AT VARYING PH OF AN OXISOL

Oxisols comprise large soil group in tropical America. These soils are acidic and have low fertility. Use of tropical legume cover crops in cropping systems is an important strategy to improve fertility of these soils for sustainable crop production. Data are limited on nutrient uptake and use efficiency of tropical cover crops under different acidity levels. The objective of our study was to evaluate growth and nutrient uptake parameters of sixteen tropical legume cover crops under three soil pH (5.1, 6.5, and 7.0) of an Oxisol. Shoot dry weight was influenced significantly by pH and cover crop treatments and their interactions, indicating that cover crops used had differential responses to changing soil pH levels. Overall, shoot dry weight decreased when soil pH was raised from 5.1 to 7.0, indicating acidity tolerance of cover crops. Nutrient concentration (content per unit of dry weight), uptake (concentration X dry weight), and nutrient use efficiency (dry weight of shoot per unit of nutrient uptake) varied significantly among cover crops. The variation in nutrient uptake and use efficiency among cover crop species was associated with variation in shoot dry matter production. Significant variation among crop species in dry matter production and low C/N ratios (average value of 14.25) suggest that cover crops which produced higher dry matter yield like white jack bean, gray mucuna bean, black mucuna bean, mucuna bean ana, and lablab are important choices for planting in tropical soils to recover large amount of macro and micronutrients, and to prevent such nutrient leaching in soil plant systems.     

Drought risk to agricultural land in Northeast and Central Germany

Aim of the study was the evaluation of the present state and further development of drought risk to agricultural sites in Northeast (NE) and Central Germany in consideration of climate changes. Based on the Medium Scale Agricultural Site Map, soil‐hydrological data were derived for heterogeneous soil areas. They refer to the landscapes in NE and Central Germany characterized by low precipitation, marked spatial soil heterogeneity, and a high share of hydromorphic soils. The soil data were linked with long‐term climate records of 368 stations for the period 1951–2000 as well as a climate scenario for the period 2001–2055. The plant water supply was calculated for three crop groups: cereals, root crops, and grass. The current and future development of drought risk of agricultural land of NE and Central Germany was evaluated. Starting in 1951, the water supply over the vegetation period has been decreasing with time for all crop groups up to now and may continue up to the year 2055 at most sites. However, there are also regions with increased plant water supply. The federal states of Brandenburg and Saxony‐Anhalt showed the strongest water deficit. Especially in these states, the plant water supply is strongly limited for cereals already today and probably may get worse for all crops in the future. On an average of the years, drought may limit plant growth in parts at >40% of agricultural land. In the federal states Mecklenburg‐Western Pomerania, Saxony, and Thuringia, the plant water supply mostly will stay in an approximately sufficient range due to higher precipitation and more favorable soil quality. The results are a background for the assessment of land‐use planning and evaluation of current and future soil‐ and site‐specific crop growing suitability on a medium scale.     

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.     

Influence of irrigation on dry matter production,leaf composition,and nutrient removal by turnip

Irrigation scheduling of leafy greens generally consists of applying 19 mm of water every four days, which leads to irrigation depths that exceed the soil water deficit, and requires fertilizer applications higher than recommended rates. We determined the influence of irrigation scheduled by class A pan evaporation and a variable crop factor on leaf tissue composition and nutrient removal by turnips using a continuous moisture gradient and different N fertilizer conditions. Irrigation maintained foliar concentrations of N, P, K, Ca, and Mg in the sufficiency range. During dry periods, increasing irrigation increased P, decreased Mg, and had little effect on N, Ca, or K foliar concentrations. Micro‐nutrient concentrations in the leaves responded to irrigation rates, but within a narrow range. Excessive water applications, due to rainfall or to irrigation rates higher than the model rate, consistently reduced nutrient crop removal. Since a combination of water applications that did not exceed soil water deficit and current fertilizer applications maintained adequate nutrient status and maximized nutrient crop removal, apparent need for N fertilization in excess of the recommended rate for turnips is due to excessive water applications.     

Soil physical changes and maize growth in a structurally fragile tropical soil due to mulching and duration between irrigation intervals

Under tropical meteorological conditions, the volume of soil explored by plant roots is crucial for crop growth as it allows increased water and nutrient use efficiency. We hypothesized that, under different irrigation intervals, leguminous mulch can extend the duration between irrigation events but maintain crop performance, because decreased evaporative fluxes also reduce constraints to root exploration imposed by mechanical stress. We evaluated the combined effects of leguminous mulch and irrigation intervals on soil physical properties to determine whether the growth and productivity of maize were modified in a structurally fragile tropical soil. The experiment involved the following treatments: 4‐day irrigation intervals with soil mulched (4C) or bare (4S), 6‐day irrigation intervals with soil mulched (6C) or bare (6S), 8‐day irrigation intervals with soil mulched (8C) or bare (8S) and 10‐day irrigation intervals with soil mulched (10C) or bare (10S). Mulch decreased soil penetration resistance and increased to 4 days the favourable time for root development in drying soil. Relative to bare soil, mulch with a 6‐day irrigation interval almost doubled nitrogen uptake post‐tasselling, which decreased nitrogen remobilization and increased the crop growth rate during this stage. These conditions had a positive effect on the transpiration rate and stomatal conductance as well as on the growth and yield of maize. A 6‐day irrigation interval with mulch compared to 4 days with bare soil resulted in similar conditions for root development, but greater uptake of nitrogen (102.73–78.70 kg/ha) and better yield (6.2–5.3 t/ha), which means greater efficiency in nitrogen and water use.     

Root growth,nutrient uptake and use efficiency by roots of tropical legume cover crops as influenced by phosphorus fertilization

The root is an important organ which supplies water and nutrients to growing plants. Data related to root growth and nutrient uptake by tropical legume cover crops are limited. The objective of this study was to evaluate root growth of tropical legume cover crops and nutrient uptake and use efficiency under different phosphorus (P) levels. The P levels used were 0 (low), 100 (medium) and 200 (high) mg kg^?1 of soil and 5 cover crops were evaluated. Root dry weight, maximum root length, specific root length were significantly influenced by P and cover crop treatments. Maximum values of these root growth parameters were achieved with the addition of 100 mg P kg^?1 soil. The P X cover crops interaction for all the macro and micronutrients, except manganese (Mn) was significant, indicating variation in uptake pattern of these nutrients by cover crops with the variation in P rates. Overall, uptake pattern of macronutrients was in the order of nitrogen>calcium>potassium>magnesium>phosphorus (N > Ca > K > Mg > P) and micronutrient uptake pattern was in the order of iron>manganese>zinc>copper (Fe > Mn > Zn > Cu). Cover crops which produced maximum root dry weight also accumulated higher amount of nutrients, including N compared to cover crops which produced lower root dry weight. Higher uptake of N compared to other nutrients by cover crops indicated that use of cover crops in the cropping systems can reduce loss of nitrate (NO₃^?) from soil-plant systems. Increase in root length and root dry weight with the addition of P can improve nutrient uptake from the soil and less loss of macro and micronutrients from the soil-plant systems.     

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.     

微润灌对作物产量及水分利用效率的影响

为探明微润灌对作物生长及产量的影响,以夏玉米和冬小麦为研究对象,采用完全随机试验设计,对比研究微润灌不同毛管间距布置(20 cm、40 cm、60 cm)、地下滴灌和无灌溉对大田作物产量、水分利用效率和土壤电导率的影响。结果表明:与地下滴灌相比,微润灌用水量约为地下滴灌的1/4~4/5;由于灌水差异较大,作物产量有所降低,夏玉米产量显著下降(P0.05),冬小麦产量下降,但未达显著水平(P0.05);两作物水分利用效率有所提高,但差异不显著(P0.05);灌溉水分利用效率均显著提高(P0.05)。随微润管布置间距的减小,作物产量呈增加趋势,作物水分利用效率与灌溉水分利用效率均呈减小趋势。综合考虑分析,在较为缺水的塿土区微润管最佳布置间距60 cm,此时可不显著降低产量同时提高水分利用效率。此外,微润灌布置间距对土壤电导率的影响较小。采用微润灌与地下滴灌处理时,随土层深增加,作物各生育期土壤电导率无显著差异(P0.05)且变化趋势基本一致,表明微润灌与地下滴灌对土壤的影响具有一致性。微润灌下作物产量与灌浆成熟期10~20 cm土层土壤电导率和10~80 cm土层土壤平均电导率之间相关性显著。因此,采用灌浆成熟期10~20 cm土层土壤电导率或10~80 cm土层土壤平均电导率预估微润灌下的作物产量具有可行性。上述研究可为微润灌技术推广应用提供依据。     

微润灌溉技术研究进展及展望

[目的]对近年来国内外关于微润灌溉技术的研究成果进行综述,探讨微润灌溉的未来研究方向,为微润灌溉制度和灌溉参数的制定及该节水技术的推广提供依据。[方法]总结微润灌溉的发展历程和应用现状,微润灌溉条件下土壤水分运动规律,微润灌溉对作物生长的影响,并分析微润灌溉技术的不足之处。[结果]微润灌溉是一种新型地下灌溉技术,以连续灌溉方式不间断地向作物根系供应适量水分,使植物吸水过程与田间灌溉过程具有同步性,灌水量与植物耗水量相匹配,实现无胁迫灌溉,改善作物品质和产量。该技术已成为国际领先的仿生型连续灌溉系统,在干旱半干旱地区具有广阔的应用前景。[结论]今后应加强的研究领域主要包括:微润灌溉对土壤养分运移的影响;微润灌溉对不同种植模式作物生长的影响;微润灌溉对农田生态系统温室气体排放的影响。     

分根区交替灌溉对马铃薯水氮利用效率的影响（简报）

分根区交替灌溉已被证实是一种有效节水灌溉技术同时保持作物产量,但有关分根区交替灌溉提高作物氮素利用效率、降低对水土环境的影响机理还不是很清楚。为了探明地下滴灌条件下充分灌溉及分根区交替灌溉（APRI）对马铃薯水氮利用效率的影响,通过田间小区试验,对各处理马铃薯全生育期灌水量、植株体氮素残留、土壤氮素残留及水氮利用效率进行了比较分析。研究结果表明：收获后,APRI处理（E、I、K）与充分灌水处理产量（F、J、L）差异不大,但APRI处理灌溉水利用效率显著高于充分灌水处理（p=0.05）;充分灌水处理不同土层（0～ 30 cm和30～60 cm）土壤中残留硝态氮、矿物质氮较APRI处理高;APRI处理（I、K）作物氮利用效率及农田氮利用效率显著高于充分灌水处理（J、L）（p=0.05）。因此,APRI处理不仅能够显著提高作物的水分利用效率,而且还能显著提高土壤矿质氮的活性,有利于作物对土壤氮素的吸收利用。     

Root Growth,Nutrient Uptake,and Nutrient-Use Efficiency by Roots of Tropical Legume Cover Crops as Influenced by Phosphorus Fertilization

Roots are important organs that supply water and nutrients to growing plants. Data related to root growth and nutrient uptake by tropical legume cover crops are limited. The objective of this study was to evaluate root growth of tropical legume cover crops and nutrient uptake and use efficiency under different phosphorus (P) levels. The P levels used were 0 (low), 100 (medium), and 200 (high) mg kg^?1 of soil, and five cover crops were evaluated. Root dry weight, maximum root length, and specific root length were significantly influenced by P and cover crop treatments. Maximum values of these root growth parameters were achieved with the addition of 100 mg P kg^?1 soil. The P?×?cover crops interactions for all the macro- and micronutrients, except manganese (Mn), were significant, indicating variation in uptake pattern of these nutrients by cover crops with the variation in P rates. Overall, uptake pattern of macronutrients was in the order of nitrogen (N) > calcium (Ca) > potassium (K) > magnesium (Mg) > P and micronutrient uptake pattern was in the order of iron (Fe) > Mn > zinc (Zn) > copper (Cu). Cover crops which produced maximum root dry weight also accumulated greater amount of nutrients, including N, compared to cover crops, which produced lower root dry weight. Greater uptake of N compared to other nutrients by cover crops indicated that use of cover crops in the cropping systems could reduce loss of nitrate (NO₃ ^?) from soil–plant systems. Increase in root length and root dry weight with the addition of P can improve nutrient uptake from the soil and lessen loss of macro- and micronutrients from the soil–plant systems.     

Nutrient mobilization and nutrient contents of Zea mays in response to EDTA additions to heavy‐metal‐contaminated agricultural soil

Enhanced phytoextraction of heavy metals (HMs) using chelating agents and agricultural crops is widely tested as remediation technique for agricultural soils contaminated with less mobile HMs. Nutrients are complexed by chelating agents simultaneously to HMs. In this study, the effect of EDTA (ethylenediaminetetraacetic acid) application on nutrient mobility in the soil and nutrient contents of Zea mays was tested on the laboratory and on the field scale. EDTA effectively increased the mobility of total water‐soluble macronutrients (Ca, K, Mg, P) and micronutrients (Fe, Mn) in the soil solution. Thereby nutrient co‐mobilization did cause competition to target HMs during the phytoextraction process. Mobilization was caused by complexation of nutrient cations by negatively charged EDTA and by dissolution of oxides and hydroxides. Increased concentrations of negatively charged P indicate the dissolution of metal phosphates by EDTA. Higher total water‐soluble nutrient concentrations enhanced bioavailability and plant contents of all determined nutrients especially that of Fe. Mobilization of nutrients may result in leaching and loss of soil fertility.