Runoff,sediment and nutrient losses from various tillage systems of cotton

Runoff, sediment and nutrient losses were studied from 3 tillage systems of cotton (Gossypium hirsutum L. ‘McNair 235’): (1) no-till without a cover crop (NT); (2) reduced-till with a winter wheat (Triticum aestivum L. ‘Coker 747’) as a cover crop (RTC); (3) conventional-till (CT) in the Tennessee Valley of north Alabama during the 1985 growing season. Runoff samples were collected from natural rainfall events and analyzed for sediment and nutrient losses.Among the 3 tillage systems the RTC system was the most effective in reducing the surface runoff, sediment and nutrient losses while maintaining comparable crop yield. Runoff and sediment concentrations from the CT system were high during the “critical period” (from planting to the last cultivation of the CT system). During the “non-critical period” (between the last cultivation of the CT system to harvesting) sediment concentrations from all tillage systems were relatively low even with high-runoff events. Summer cultivations reduced both surface runoff and sediment concentrations from the CT system. This may signify that a combination of conservation tillage and summer cultivation has the potential for controlling weeds without enhancing soil erosion.Concentration of ammonium nitrogen (NH₄-N) and soluble-phosphorus concentration in surface runoff were higher than the recommended standard level for public water supplies and the growth of algae, respectively. Concentration of nitrate nitrogen (NO₃-N) in the surface runoff was well within the upper limit for drinking water.     

植被覆盖和雨强对附着在沉积物上的养分流失, 泥沙颗粒组成及体积分形维数的影响

Vegetation and rainfall are two important factors affecting soil erosion and thus resulting in nutrient loss in the Chinese Loess Plateau.A field experiment was conducted to investigate the effects of rainfall intensities(60,100 and 140 mm h-1) and vegetation(Caragana korshinskii) coverages(0%,30% and 80%) on soil loss,nutrient loss,and the composition and volume fractal dimension of eroded sediment particles under simulated rainfall conditions.The results showed that vegetation cover,rainfall intensity and their interaction all had significant effects on sediment transport and the sedimentbound nutrient loss.Higher rainfall intensity and lower coverage led to higher sediment and nutrient losses.Positive linear relationships were observed between soil loss and nutrient loss.The treatments showed more significant effects on the enrichment ratio(ER) of nitrogen(ERN) than organic matter(EROM) and phosphorus(ERP).Compared with the original surface soil,the eroded sediment contained more fine particles.Under the same coverage,the clay content significantly decreased with increasing rainfall intensity.The ER of sediment-bound nutrients was positively correlated with that of clay,suggesting that the clay fraction was preferentially eroded and soil nutrients were mainly adsorbed onto or contained within this fraction.There were increments in the fractal dimension of the sediment particles compared to that of the original surface soil.Moreover,the fractal dimension was positively correlated with clay,silt,and sediment-bound OM,N,and P contents,whereas it was negatively correlated with sand content.This study demonstrated that fractal dimension analysis can be used to characterize differences in particle-size distribution and nutrient loss associated with soil erosion.     

Partition Isotherms of Chlorobenzenes in a Sediment–Water System

Partition experiments for a series of chlorobenzenes, 1,4-dichlorobenzene (1,4-DCB), 1,3,5-trichlorobenzene (1,3,5-TCB), 1,2,4,5-tetrachlorobenzene (1,2,4,5-TeCB), pentachlorobenzene (QCB), and hexochlorobenzene (HCB), in a sediment–water system were carried out and the sediment–water partition isotherms for the chlorobenzenes were determined. The partition isotherms were well described by the linear and the Langmuir models. However, experimental data indicated that the partition isotherms exhibited nonlinear trends at high concentrations. The maximum concentrations that can be adsorbed from the Langmuir model decreased with K _OW values of the chlorobenzenes. QSAR analysis showed that strong relationships exist between the partition parameters (partition coefficients and maximum concentration that can be adsorbed) and physicochemical properties (molar volume, solubility in water, and K _OW values).     

流溪河水库流域碳氮营养盐浓度的时空变化特征及其影响因素

流溪河水库流域是亚热带典型的山地河源区,研究此流域的碳氮营养盐浓度时空变化特征及其影响因素对揭示亚热带流域生物地球化学循环与保障水资源供给具有重要意义.基于地形、气象、土地利用、土壤和实地采样获得的水质数据,采用相关分析及Elastic Net回归分析法,探讨了流溪河水库流域溪流碳氮营养盐浓度的时空变化特征及其影响因素...     

Coupling among applied,soil, root,and top components for forage crop production

Abstract

This analysis establishes linkage among (a) applied nutrients nitrogen (N), phosphorus (P), and potassium (K), (b) available soil nutrients, (c) root dry matter and nutrient content, (d) top dry matter and nutrient content, and (e) leaf area and carbon dioxide (CO₂) concentration. It was previously shown that (a) and (d) are coupled by logistic equations with a common response coefficient c between dry matter and plant nutrient uptake with each applied nutrient. As a consequence of the common c, it has been shown that dry matter and plant nutrient removal are coupled by a hyperbolic equation. Furthermore, a model has been developed which includes N, P, and K as inputs. In the present work, (a) and (b) were coupled by a logistic equation as were (a) and (c). It was then shown that plant nutrient removal was coupled to available soil nutrients through a hyperbolic equation. The hyperbolic relationship was also shown to link dry matter between roots and tops, as well as plant N removal between roots and tops. As a consequence of the results above, it was then concluded that root nutrient content is related to available soil nutrient through a hyperbolic equation. The detailed mechanism of this coupling was not identified. Leaf area of soybeans followed a hyperbolic relationship with CO₂ concentration in the canopy.     

肥液浓度和生物质掺混比例对微润灌溉湿润体内水肥分布的影响

微润灌溉作为一种新型地下连续灌溉节水技术,可为农业水肥一体化提供有效载体。为探明不同生物质掺混比例下竖插式微润灌溉施肥湿润体内水分和养分的分布规律,开展室内入渗试验,设置3个肥液浓度（清水F₀：0 g·L^-1;低浓度F_L：0.2 g·L^-1;高浓度F_H：0.4 g·L^-1）和4个土壤生物质（花生壳粉末）掺混比例（无掺混B₀：0;低掺混B_L：1.5%;中掺混B_M：3.0%;高掺混B_H：4.5%）,研究微润灌溉施肥湿润体内土壤含水率、硝态氮、速效磷和速效钾的分布特性。结果表明：掺混生物质后湿润体内水肥分布范围显著增大,而肥液浓度对水肥分布范围的影响不显著。土壤水肥含量随着与微润管水平距离的增加而逐渐减小,水肥含量最大值出现在微润管周围。在与微润管水平距离为0~10 cm范围内,土壤含水率和硝态氮分布较均匀,速效磷和速效钾则形成累积区。肥液浓度和生物质掺混比例对湿润体内水肥含量均值影响显著。与F₀相比,增加肥液浓度提高土壤含水率和养分（硝态氮、速效磷和速效钾）含量均值3.94%~14.09%和124.92%~458.05%;与B₀相比,增大生物质掺混比例提高土壤含水率和养分含量均值12.89%~33.32%和28.37%~115.44%。微润灌溉施肥湿润体内土壤含水率和硝态氮的分布均匀性较高,而速效磷和速效钾分布均匀性较低。增大肥液浓度和生物质掺混比例可提高湿润体内土壤含水率和硝态氮的分布均匀系数,而降低速效磷和速效钾的分布均匀系数。微润灌溉施肥湿润体内水肥含量均值与至微润管水平距离的关系符合四参数Log-logistic模型。总之,在土壤中掺混生物质有利于微润灌溉施肥下水分和养分的运移,增加肥液浓度和土壤生物质掺混比例可显著提高湿润体内的水肥含量,增大水分和硝态氮的分布均匀性,促使速效磷和速效钾在微润管周围的累积量增多。研究结果可为微润灌溉水肥一体化技术提供理论依据和实践参考。     

丹江口库区土壤氮磷养分流失特征

[目的]研究丹江口库区土壤的水土流失和非点源污染物氮磷流失的特点,为农业非点源污染模型的建立提供理论依据。[方法]通过室内人工模拟降雨试验,研究了坡度和施肥等处理对产流产沙、氮磷养分(硝态氮、铵态氮、总氮、有效磷和总磷)流失特点的影响。[结果](1)随着坡度的增加,平均入渗率和初始产流时间呈减小趋势,而径流总量和泥沙总量呈增加趋势。(2)相同施肥处理下,随着坡度的增加,泥沙中硝态氮、总氮、有效磷和总磷的流失浓度呈减小趋势,铵态氮流失浓度在不施氮肥条件下呈减小趋势,而在施氮肥处理下呈增加趋势。(3)在相同坡度条件下,随降雨时间推移,总氮浓度呈先减小后趋于稳定的趋势;铵态氮浓度随施肥处理的变化均呈现出波浪形变化;在施氮肥时,径流中硝态氮的浓度随着时间的推移,呈逐渐减小并趋于平缓的趋势,而在不施氮肥时几乎无变化。[结论]在不同施肥措施和坡度条件下,硝态氮主要随径流而流失,为随泥沙流失的8~11倍;铵态氮主要是随径流泥沙而流失,为随径流流失的1~17倍;总氮则是随径流和径流泥沙共同流失;有效磷和总磷都是以泥沙结合态流失为主,分别为随径流流失的1 000~6 200和1~3倍。     

加速土壤侵蚀对养分流失的影响

Soil erosion and nutrient losses on newly-deforested lands in the Ziwuling Region on the Loess Plateau of China were monitored to quantitatively evaluate the effects of accelerated soil erosion, caused by deforestation, on organic matter, nitrogen and phosphorus losses. Eight natural runoff plots were established on the loessial hill slopes representing different erosion patterns of dominant erosion processes including sheet, rill and shallow gully （similar to ephemeral gully）. Sediment samples were collected after each erosive rainfall event. Results showed that soil nutrients losses increased with an increase of erosion intensity. Linear relations between the losses of organic matter, total N, NH4-N, and available P and erosion intensity were found. Nutrient content per unit amount of eroded sediment decreased from the sheet to the shallow gully erosion zones, whereas total nutrient loss increased. Compared with topsoil, nutrients in eroded sediment were enriched, especially available P and NH4-N. The intensity of soil nutrient losses was also closely related to soil erosion intensity and pattern with the most severe soil erosion and nutrient loss occurring in the shallow gully channels on loessial hill slopes. These research findings will help to improve the understanding of the relation between accelerated erosion process after deforestation and soil quality degradation and to design better eco-environmental rehabilitation schemes for the Loess Plateau.     

黄土区裸露坡地径流养分流失模型的建立与验证

在自然降雨条件下,黄土区坡耕地土壤表层中的养分会随地表径流流失,从而加剧了土壤质量和生产力的下降并造成严重的农业面源污染,使得准确预测黄土区养分随地表径流的流失过程尤为重要.现有的养分流失模型着重于估算长时段的养分流失总量,且未考虑开始产流前入渗水对交换层养分的稀释作用.根据不同降雨时段的养分迁移特性,将整个降雨过程划...     

Predicting Water, Sediment and NO3-N Loads under Scenarios of Land-use and Management Practices in a Flat Watershed

Changes in land-use or management practices may affect water outflow, sediment, nutrients and pesticides loads. Thus, there is an increasing demand for quantitative information at the watershed scale that would help decision makers or planners to take appropriate decisions. This paper evaluates by a modeling approach the impact of farming practices and land-use changes on water discharge, sediment and NO₃-N loads at the outlet of a 51.29 km² watershed of central Iowa (Walnut Creek watershed). This intensively farmed (corn-soybean rotation) watershed is characterized by a flat topography with tiles and potholes. Nine scenarios of management practices (nitrogen application rates: increase of current rate by 20, 40%, decrease of current rate by 20, 40 and 60%; no tillage) and land-use changes (from corn-soybean rotation to winter wheat and pasture) were tested over a 30 yr simulated period. The selected model (Soil and Water Assessment Tool, SWAT) was first validated using observed flow, sediment and nutrient loads from 1991 to 1998. Scenarios of N application rates did not affect water and sediment annual budgets but did so for NO₃-N loads. Lessening the N rate by 20, 40 and 60% in corn-soybean fields decreased mean NO₃-N annual loads by 22, 50 and 95%, respectively, with greatest differences during late spring. On the other hand, increasing input N by 20 and 40% enhanced NO₃-N loads by 25 and 49%, respectively. When replacing corn-soybean rotation by winter wheat, NO₃-N loads increased in early fall, immediately after harvest. Pasture installation with or without fertilization lessened flow discharge, NO₃-N and sediment delivery by 58, 97 and 50%, respectively. No-tillage practices did not significantly affect the water resource and sediment loads. Finally, such realistic predictions of the impact of farming systems scenarios over a long period are discussed regarding environmental processes involved.     

影响富营养化湖泊底泥氮、磷释放的因素

[目的]分析水体酸碱度、温度以及上覆水营养盐浓度,为合理评估环境因素对湖泊底泥氮、磷释放的影响提供科学依据。[方法]选择富营氧化比较严重的云南省昆明市城市景观湖泊翠湖为研究区域,通过控制不同pH值、温度和上覆水营养盐浓度来模拟影响底泥氮磷释放的因素。[结果](1)放置时间相同条件下底泥氮、磷释放量受到水体酸碱性的影响,中性环境下(pH=7.5)释放量高于酸性和碱性水体条件。底泥释放5,10h条件下,pH值为7.5时底泥磷释放量分别达到5.88,8.28mg/kg;pH值为7.5时底泥氮释放量分别达到22.8,38.4mg/kg;(2)底泥氮、磷释放量随着温度升高而增加。温度为20℃时底泥氮、磷的释放量分别达到28.62,3.75mg/kg;(3)底泥氮、磷的释放量均随着上覆水浓度增加而减少,随着放置时间延长而增加。放置时间5h上覆水氨氮浓度0.31mg/L底泥氮的释放量最大,达到21.63mg/kg。放置10h在氨氮为2.37mg/L时底泥氮的释放量达到最大值(39.22mg/kg);底泥磷释放量在上覆水磷浓度0.14mg/L时底泥总磷的释放量最大;放置时间为5,10h时分别达到4.25,4.91mg/kg。[结论]底泥中营养盐释放是一相当复杂的动态过程,水体酸碱度、温度或上覆水营养盐浓度是影响释放量的主要因素。     

Water and nutrient dynamics of a paddy soil of Bangladesh

The objectives of the study were the changes in water tension, redox potential, and the pH value of a silty Eutric Gleysol from young river sediments near Mymensingh, the nutrient concentration of soil solution, as well as the supply of nutrients by rain, irrigation and fertilizing, and the uptake of nutrients by rice during the year. In the case of nitrogen, a moderate loss was observed, caused by the leaching of NH₄, and significant losses due to volatilisation and denitrification. Fertilized P was enriched in the soil. The leaching of Ca, K, Mg, Na, Cu, Fe, Mn, and Zn was clearly higher than the addition by rain, irrigation and fertilization. It is concluded, that the loss of nutrients was caused by weathering.     

Nutrient solution concentration on pepper grown in a soilless closed system: yield,fruit quality,water and nutrient efficiency

Abstract

The aim of the experiment was to verify how the adoption of a reduced strength nutrient solution in a soilless closed system could influence the production and quality of pepper and improve the use efficiency of water and minerals. Two nutrient solutions characterized by the same ion ratio but macronutrient concentration equal to 100% or 60% were adopted. The total yield did not differ between the treatments; however the lower concentration of nutrients determined a significant reduction of incidence of unmarketable fruits (blossom-end rot) and thus a higher marketable production (+15%). Within the fruit quality characteristics the dry matter content and the titratable acidity were significantly higher adopting the full strength nutrient solution. Important differences were found when the agronomic water use efficiency was considered: the weight of marketable pepper produced per m³ of water input was about 32% higher using the reduced concentration treatment according to the lower volume of water released in the environment due to the lower renewal of recirculated nutrient solution. A similar pattern was observed for the use efficiency of the main nutrients. With reduced strength nutrient solution the amounts of nitrogen, phosphorus and potassium released per ton of marketable tomatoes were respectively 83%, 80% and 81% lower than the control. The use of a reduced strength nutrient solution in soilless closed system for pepper cultivation did not influence the total yield and improved the use efficiency of water and minerals. Moreover, the environmental impact of the system was drastically reduced.     

Response of potatoes to different nutrient solution management in a closed hydroponic system

Ion control of nutrient solutions to control nitrogen (N), phosphorus (P), and potassium (K) was developed for Superior (medium-to-early maturing) and Atlantic (mid-late) potato cultivars grown in closed hydroponic systems in which solutions were replenished and recirculated. Results were compared with conventional nutrient solution management strategies. In the “solution replacement” treatment, nutrient solutions were completely replaced each week. In the “electrical conductivity (EC) control” treatment, water use by potato plants was compensated by adding ground water to achieve the original volume (water replenishment) and the diluted EC of the solution was adjusted to the target levels using stock solution. In “ion control” treatment, ammonium dihydrogen phosphate (NH₄H₂PO₄) and potassium nitrate (KNO₃) were added to the EC-controlled nutrient solution. The amounts increased with plant age in both cultivars. The concentrations of nitrate (NO₃), P, and K in the ion control nutrient solution could be maintained at target levels. In water replenishment, recycling of nutrient solution resulted in a progressive decrease in EC and an increase in pH. Root activity increased by 93% and 59% in the Superior and Atlantic cultivars, respectively, compared with the nutrient solution replacement. These changes decreased photosynthesis, plant growth, water use, and thus tuber growth in the Superior cultivar. Decreased growth of shoots and tubers occurred without affecting photosynthesis in the Atlantic cultivar. Although there were no significant differences in root activity, photosynthesis, or plant growth between the ion control treatment and the EC control treatment, increased tuber growth was observed in the ion control treatment, possibly as a result of the constant supply of nutrients. High tuber growth and the capability to maintain solution nutrient concentration in the ion control treatment are highly desirable for closed hydroponic systems.     

Entwicklung und Ertrag von Sommerweizen in Hydrokultur unter dem Einfluß verschiedener Ernährungsbedingungen

Development and yield of spring wheat in water culture as influenced by nutrient concentration. The development of spring wheat cv. Solo grown until maturity in nutrient solutions of normal concentration changed weekly, differs from similar plants growing in soil. In experiments in which nutrient supply was reduced at different growth stages, an attempt was made to minimize the differences. These consist mainly of permanent tillering, retarded senescing of leaves and in dry matter accumulation in the grain. 1) Reducing the total nutrient supply during the grain filling period decreases the chlorophyll-con-tent of the flag-leaf at an earlier stage and hence also its ability to assimilate CO₂. This reduction in nutrient supply has thus a beneficial effect on the development of the grain by allowing a better coordination with leaf senescence and an increase in nitrogen and dry matter transfer from the flag leaf to the grain. 2) The retarded response to a reduction of the nutrient concentration points to a “luxury consumption” in the vegetative phase. This might be the reason why it was not really possible to achieve optimal timing of vegetative and generative development. 3) After examination of the effect of lowering the nutrient supply in the vegetative phase, a nutritional design for growingspring wheat in water culture was proposed. This consists of lowering the concentration to meet the needs of plants and comprises a rise and fall of the concentration (0.25,0.5, 0.75,0.5 and 0.25 of the normal conc., see fig. 4). 4) Comparing 0.4 and 0 mMol/l N during the grain filling(other nutrients supplied according to the concept outlined above), the relevance of nitrogen for the CO₂,-assimilation capacity and more obviously for the senescence of the flag leaf was shown. Nitrogen deficiency decreases the assimilation ability within a short time and depresses grain development. These findings confirm the validity of the nutritional concept proposed.     

模拟降雨条件下北运河流域农田养分流失特征

为了解北运河流域农田养分流失特征,通过模拟降雨的情况下,分析了降雨量对径流雨水中养分含量、土壤养分和泥沙流失的变化特征。结果表明,北运河地区只有在暴雨情况下产生农田径流,暴雨后,农田径流雨水中总N浓度在4.7~11.3 mg·L-1,氨态氮和硝态氮占44.51%;总P浓度在0.66~1.35 mg·L-1,水溶磷含量占到总磷54.08%。养分的流失以表层为主,土壤表层总氮流失比例达到29.79%,氨态氮损失率达到52.09%,硝态氮损失10.21%,表层土壤总磷含量下降达到16.48%,水溶性磷损失5.27%。农田径流泥沙中总氮含量为0.66~1.27 mg·g-1,占总流失量的82.28%;总P浓度在14.73~20 mg·g-1,占到总流失量的99.89%;模拟降雨后土壤大团聚体减少8.8%,而微团聚体增加9.5%。     

Specific response of sugar beet cultivars to different nitrogen forms

Six cultivars of sugar beet characterized by different sugar contents were grown in water culture on Reid-York nutrient solution for 30 days. Nitrogen was included in the medium in the form of either NH₄NO₃, NH₄Cl or Ca(NO₃)₂ at the concentrations 105, 210 and 420 mg N/l. The results obtained reveal that both shoot dry weight and leaf area were dependent upon the type of cultivar and the form and concentration of nitrogen present in the nutrient solution. The least amount of shoot matter and the smallest leaf area were obtained in the presence of ammonium as the sole nitrogen source. The concentration of total nitrate and ammonium nitrogen measured in the shoot was found to be dependent on the cultivar type and on the concentration of nitrogen present in the nutrient solution. The highest oxalic acid concentrations were detected in plants grown on nitrate. No synthesis of oxalic acid was detected upon growth on ammonium as the sole nitrogen source.     

Quantification of Shallow Groundwater Nutrient Dynamics in Septic Areas

Of all groundwater pollution sources, septic systems are the second largest source of groundwater nitrate contamination in USA. This study investigated shallow groundwater (SGW) nutrient dynamics in septic areas at the northern part of the Lower St. Johns River Basin, Florida, USA. Thirty-five SGW-monitoring wells, located at nine different urban areas served by septic systems, were used to collect the SGW samples seasonally and/or biweekly for a duration of 3?years from 2003 to 2006. Analytical results showed that there were 16 wells with nitrate concentrations exceeding the US Environmental Protection Agency's drinking water limit (10?mg?L^?1). There also were 11 and 14 wells with total Kjeldahl nitrogen (TKN) and total phosphorus (TP) concentrations, respectively, exceeding the ambient water quality criteria (0.9?mg?L^?1 for TKN and 0.04?mg?L^?1 for TP) recommended for rivers and streams in nutrient Ecoregion XII (Southeast USA). In general, site variations are much greater than seasonal variations in SGW nutrient concentrations. A negative correlation existed between nitrate/nitrite?Cnitrogen (NO_x?CN) and TKN as well as between NO_x?CN and ammonium ( $ NH_4^{ + } $ ), whereas a positive correlation occurred between TKN and $ NH_4^{ + } $ . Furthermore, a positive correlation was found between reduction and oxidation (redox) potential and water level, while no correlation was observed between potassium concentration and redox potential. This study demonstrates a need to investigate the potential adverse impacts of SGW nutrients from the septic areas upon the deeper groundwater quality due to the nutrient penetration and upon the surface water quality due to the nutrient discharge.     

Growth and nutritional disorders of coffee cultivated in nutrient solutions with suppressed macronutrients

The objective was to evaluate the effect of omitting macronutrients in the nutrients solution on growth characteristics and nutritional status of coffee. The treatments were complete nutrients solutions and solutions with nutrient omission: N (nitrogen), P (phosphorus), K (potassium), Ca (calcium), Mg (magnesium) and S (sulfur). The experiment was carried out under greenhouse conditions with 3 replicates in a completely random design. Plant height, number of leaves per plant, stem diameter, relative chlorophyll index, photosynthesis rate, stomatal conductance, transpiration, carbon dioxide (CO₂) concentration, dry matter, content levels of macronutrients in plant aerial part and root system, and nutritional disorders were evaluated. Macronutrients suppression affected nutrients concentration in many plant parts, inducing the appearance of symptoms characteristic of each nutrient. The most limiting nutrients for coffee plants development were nitrogen and calcium, reflected in the lower dry matter accumulation and nitrogen the most required.     

四川省龙泉湖表层沉积物与表层水体中各种形态氮含量及其相关关系

以四川省龙泉湖湖泊表层沉积物和表层水体为研究对象,分析了表层沉积物的各种水溶性氮含量和表层水体的硝态氮和氨氮的含量。结果表明,表层沉积物中水溶性总氮、水溶性氨氮和水溶性硝态氮的平均含量分别为6.64,1.22和2.83mg/kg,水体中硝态氮和氨氮的平均含量分别为5.09和0.05mg/L;表层水体和表层沉积物中的硝态氮含量无显著相关关系,但表层水体和表层沉积物中的氨氮含量呈显著正相关,说明表层水体中氨氮可能是由沉积物释放而来。