Investigation on Phosphate Solubilization Potential of Agricultural Soil Bacteria as Affected by Different Phosphorus Sources,Temperature, Salt,and pH

Ten phosphate-solubilizing bacterial strains belonging to genera Pseudomonas, Burkholderia, Enterobacter, Serratia, Klebsiella, and Aeromonas were tested for mineral phosphate solubilization activity in Pikovskaya's broth using different phosphate sources at four temperatures (15, 25, 35, and 45 ^οC). Dicalcium and tricalcium phosphate were solubilized more effectively (≥1000 mg L^?1) than ferric and rock phosphate (≥100 mg L^?1) and 35 °C was found to be the optimum temperature. Although Klebsiella and Aeromonas spp. are well known for their dinitrogen (N₂)–fixing ability, to the best of our knowledge, this is the first report of inorganic phosphate solubilization by Klebsiella terrigena and Aeromonas vaga. Interestingly, A. vaga BAM-77 is the most efficient strain at solubilizing inorganic phosphorus (P) even in the presence of 8% sodium chloride (NaCl) at pH 10. These findings indicate that all four strains are efficient P solubilizers under variable conditions of temperature, pH, and P source and thus can be recommended for P fertilization in different soils.     

Effects of Nitrogen Application on Chlorophyll Content,Water Relations,and Yield of Maize Hybrids under Saline Conditions

An experiment was conducted to assess whether accumulation of photosynthetic pigments, proline, and maintenance of water relation attributes relate to the yield of maize hybrids differing in salt tolerance. Two maize hybrids, Pioneer32B33 and Dekalb979, were grown at three salinity levels under four nitrogen treatments. The experiment was laid out in a three-factor randomized complete block design and there were three replications of each treatment. Salt stress significantly decreased leaf chlorophyll a and a/b contents, whereas chlorophyll b and total chlorophyll were slightly increased. Under salinity stress, relative water content decreased, and water potential and osmotic potential become more negative. As a result, turgor potential also decreased. Nitrogen application improved all the chlorophyll pigments, water-related attributes, and yield components. However, chlorophyll a/b ratio was decreased. Overall, because of the differential response of maize hybrids to salt stress in terms of their performance in photosynthetic pigments, water relations, and yield, it can be concluded that hybrid Pioneer32B33 might perform better, if grown under salinity regime and sufficient nitrogen was applied in the growth medium.     

Impact of Varying Ca/Mg Waters on Ionic Balance,Dispersion, and Clay Flocculation of Salt-Affected Soils

Inceptisols and Vertisols are two dominant soil orders that support major agricultural production in India. These soils often exist in semi-arid and arid regions. Low precipitation and high evaporation demand leads to salt accumulation in these areas. The problem of salt accumulation is further compounded by the presence of saline/alkaline groundwaters. We evaluated the effect of modified Ca/Mg waters on ionic composition, dispersion, and clay flocculation of sodic Inceptisols, saline-sodic Inceptisols, and normal Vertisols from different parts of India. A completely randomized factorial design with three replications of individual soils were sequentially leached with five pore volumes of deionized, saline water of 60 and 120 me L^?1 total electrolyte concentration (TEC) at a fixed SAR of 5.0 mmol^1/2 L^?1/2 and Ca:Mg ratio of 2:1, 1:1 and 1:2. Application of saline waters decreased pH and increased EC of the soil leachates after leaching five pore volumes of three Ca/Mg ratios of 60 and 120 me L^?1 solutions in sodic Inceptisols and normal Vertisols. In saline-sodic Inceptisols, application of saline waters decreased both pH and electrical conductivity (EC) of the soil leachates. Preferential Ca²⁺ holding in soil was only noticed in sodic Inceptisols when leaching process was performed with independent saline waters, but Mg²⁺ has a tendency to hold in soil upon application of independent saline waters for all soils except sodic Inceptisols. Periodic application of deionized water could increase soil dispersion and decreased flocculation of clay particles. Mg²⁺ ion had less flocculating vis-à-vis high-dispersion effect on soil clays than the Ca²⁺ ion.     

Potassium is responsible for salinity in soils amended with poultry manure

Abstract

Soil salinity increases when heavy rates of poultry manure are applied to sandy coastal plain soils. Analysis of soils involved in a poultry manure study during 1970, 1971 and 1972 has shown that soil salinity is primarily associated with a high concentration of ? in the soil solution. Although concentrations of other elements increased with the application of poultry manure also, the increases were not sufficient to account for the salinity in these soils.     

Biomass Production,Forage Quality,and Cation Uptake of Quail Bush,Four‐Wing Saltbush,and Seaside Barley irrigated with Moderately Saline–Sodic Water

Abstract: Beneficial use of water of impaired quality has gained attention globally as society's demand for domestic quality water has increased. Additionally, concerns about the environmental implications of disposal of water of impaired quality have necessitated assessment of alternatives to disposal of such water. The study reported here investigated capacity of Atriplex lentiformis (Torr.) S. Wats. (Quail bush), Atriplex X aptera A. Nels. (pro sp.) (Wytana four‐wing saltbush), and Hordeum marinum Huds. (seaside barley) to produce biomass and crude protein and take up cations when irrigated with moderately saline–sodic water, in the presence of a shallow water table. Water tables were established at 0.38, 0.76, and 1.14 m below the surface in sand‐filled columns. The columns were then planted to the study species. Study plants were irrigated for 224 days; irrigation water was supplied every 7 days equal to water lost to evapotranspiration (ET) plus 100 mL (the volume of water removed in the most previous soil solution sampling). Water representing one of two irrigation sources was used: Powder River (PR) [electrical conductivity (EC) = 0.19 Sm^?1, sodium adsorption ratio (SAR) = 3.5 (mmol_c L^?1)^1/2 ] or coalbed natural gas (CBNG) wastewater [EC = 0.35 Sm^?1, SAR = 10.5 (mmol_c L^?1)^1/2]. Biomass production did not differ significantly between water quality treatments but did differ significantly among species and water table depth within species. Averaged across water quality treatments, Hordeum marinum produced 79% more biomass than A. lentiformis and 122% more biomass than Atriplex X aptera, but contained only 11% crude protein compared to 16% crude protein in A. lentiformis and 14% crude protein in Atriplex X aptera. Atriplex spp. grown in columns with the water table at 0.38 m depth produced more biomass, took up less calcium (Ca²⁺) on a percentage basis [(g Ca²⁺ g^?1 biomass) ×100], and took up more sodium (Na⁺) on a percentage basis than when grown with the water table at a deeper depth. Uptake of cations by Atriplex lentiformis was approximately twice the uptake of cations by Atriplex X aptera and three times that of H. marinum. After 224 days of irrigation, crop growth, and cation uptake, followed by biomass harvest, EC and SAR of shallow groundwater in columns planted to A. lentiformis were less than EC and SAR of shallow ground water in columns planted to either of the other species.     

Influence of Salt Stress on the Nutritional State of Cordyline fruticosa var. Red Edge, 2: Sodium,Potassium, Calcium,and Magnesium

The aim of this trial was to study the nutritional behavior generated by modifications in the salt concentration in the nutrient solution used for the fertigation of Cordyline fruticosa var. Red Edge plants. Four treatments were tested: T₁ [control, 1.5 dS m^?1, 14.3 mmol L^?1 sodium chloride (NaCl)]; T₂ (2.5 dS m^?1, 22.2 mmol L^?1 NaCl); T₃ (3.5 dS m^?1, 32.7 mmol L^?1 NaCl); and T₄ (4.5 dS m^?1, 38.2 mmol L^?1 NaCl). There is an accumulation of sodium (Na⁺) in roots, stem, and petiole when salinity increases, which avoid leaf damages. Potassium (K) concentration increases with the intermediate saline treatments in stems and leaves but decreases when plants are fertigated with T₄. Calcium (Ca) accumulates in roots with T₃ and T₄, in stems with T₄, and in petioles and leaves with T₃. Magnesium (Mg) concentration is greater in stems, petioles, and leaves of T₄, but is greater in roots of T₃. Plants fertigated with the three saline treatments extract 1.4 times more Na⁺ than T₁ plants. The greatest K⁺ extraction is observed in T₂, followed by T₃, and T₄. T₂, T₃, and T₄ plants extracted more Ca²⁺ than T₁ plants. Finally, Mg²⁺ extractions in T₃ are twice as much as they are in T₁, while in T₄ and T₂ are much greater.     

Nitrogen fertigation of greenhouse‐grown tomato

Abstract

This greenhouse study was conducted to determine the response of trickle‐irrigated tomato (Lycopersicon esculentum cv. Dombo) to 6.4, 12.8, or 19.2 mmol N/L applied via the irrigation stream. The plants were grown in pots filled with 12 kg of soil. The amount of N applied in a total of 438 L of water per plant was 39.4, 78.8, or 118.2 g for the three N levels, respectively. The residual NO₃‐N concentration in the root volume was negligible with the 6.4 mmol N/L treatment, whereas, with the highest N level increased sharply for the first 16 weeks before reaching a value around 32 mmol N/L, which continued for the remainder of the experiment. With the highest N level there was also increase of soil solution EC, and NO₃‐N concentration in laminae and petioles was in excess. With the lowest N treatment, NO₃‐N concentration in laminae and petioles was at deficient levels. With 12.8 mmol N/L, NO₃‐N in petioles and laminae was at the sufficient level and yet no substantial increase of soil solution EC or NO₃‐N concentration occurred, suggesting efficient use of N by crop. The highest yield (12.6 kg marketable fresh fruit per plant) was obtained with 12.8 mmol N/L due to increased number of fresh weight of fruits. It was concluded that 12.8 mmol N/L applied via the irrigation stream is adequate for high tomato yield without unduly raising soil salinity or wasting fertilizer N.     

于田绿洲典型区域土壤盐分空间分异规律研究

应用地统计学方法对于田绿洲典型区域土壤盐分空间分异规律进行了研究。结果表明,于田绿洲土壤盐渍化严重并表现出表聚现象。由于人类活动干扰,表层土壤盐分变幅最大;0—5cm土层土壤盐分表现出强烈的空间相关性,5—30cm土层次之,30—70cm土层土壤盐分的空间相关性很弱。水平方向上,0—30cm土层中土壤盐分从东向西先增大,后减小,再增大,再减小;30—70cm土层中土壤盐分从东向西逐渐减小;研究区南北两侧土壤盐分含量高,中部盐分含量低。垂直方向上,盐碱地和高、中密度草地土壤盐分含量较高,呈现出自上而下逐渐减小的分布趋势。其中盐碱地土壤盐分含量最高,高密度草地土壤盐分的垂直变化幅度大于中密度草地,低密度草地和农田土壤盐分含量较低,且垂直变化不大。不同地形和土地利用带来的土壤水分运动差异,是绿洲土壤盐分空间分异的主导因素。     

河套灌区玉米耐盐性分析及生态适宜区划分

为了探讨河套灌区盐碱地玉米对根区土壤盐分的生态适应性,本文基于田间定位观测,运用非线性最小二乘数值逼近法建立玉米耐盐函数模型;同时根据耐盐性分析,提出玉米在该灌区不同生态适宜区的划分标准。结果表明,盐碱地地膜覆盖在生产上有较好的控盐效果,可以使玉米苗期0～10、0～20和0～40cm土壤盐分分别降低61.2%、53.8%、41.3%,能够增强玉米对盐碱地的生态适应性;分段式耐盐函数模型和S型耐盐函数模型均能较好地反应玉米相对产量对浅层土壤盐分变化的响应关系;浅层0～40cm土壤盐分作为玉米根层盐分来分析玉米的耐盐性最具代表性,其对应中玉9号玉米的耐盐指数为6.583;根据耐盐性分析,将区域耕地划分为玉米最适宜区、适宜区、次适宜区和不适宜区,对应玉米苗期0～20cm膜外土壤盐分分别为低于1.178、1.178～2.036、2.036～3.465和高于3.465g/kg。本研究将为当地玉米种植合理布局、高效生产提供理论指导。     

盐度降低间歇曝气动态膜生物反应器净化水产养殖废水的效果

采用间歇曝气动态膜生物反应器(DMBR)处理不同盐度下的水产养殖废水,研究盐度对有机物降解和反硝化过程的影响。结果表明:当盐度在0～35g/L范围内,随着盐度的提高,由于盐度对微生物的抑制作用,在含盐条件下有机物降解和反硝化效率下降,间歇曝气动态膜生物反应器对水产养殖废水化学需氧量CODMn的去除率从89.5%下降到75.5%;出水总氮TN去除率从89.9%下降到74.4%。通过对有机物降解速率常数和反硝化速率常数的动力性模拟,CODMn降解速率常数和硝态氮NO3--N的降解速率常数随盐度的提高呈线性下降的趋势,其线性回归模型的决定系数分别为0.9838、0.9665。盐度对水产养殖废水反硝化过程的抑制作用要大于有机物降解过程。