JWSS - Journal of Water and Soil Science

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Nitrogen fertilizer application for corn (Zea mays L.) based on available N of soil can decrease the need to N fertilizer and, consequently, reduce the risk of environmental pollution, especially that of groundwater and drinking water. The objectives of this study were i) determining soil N0₃-N critical level at 4 to 6 leaf stage, ii) to study soil nitrate distribution, iii) determining N rate required for maximum corn grain yield, iv) measuring soil residual nitrate nitrogen after harvesting, and v) using hand chlorophyll meter to evaluate N status of corn. The experiment was conducted under field conditions in Bajgah and Kooshkak research stations (Fars Province) in 1996 using a split plot randomized complete block design with four replications. Main plots were control, 60, 120, and 180 kg N ha^-1 as urea. At 4 to 6 leaf stage each main plot was divided into two sub-plots and N was applied at 60 kg N ha^-1 rate to one sub-plot and the other sub-plot was left as control.

 Results showed that critical soil N0₃-N level at 4 to 6 leaf stage in 0-30 cm depth for 90 percent relative yield in Bajgah was 12-14 and for Kooshkak was 8-10 mg kg^-1 soil. The highest coefficient of determination between corn grain yield and soil N0₃-N in 0-30 cm depth for Bajgah was in furrow sample and for Kooshkak was in furrow and shoulder composite sample. In both sites, maximum corn grain yield, with 15.5% moisture content, was about 14 mg ha^-1 that was obtained through the application of 120 kg N ha^-1 as preplant plus 60 kg N ha^-1 as sidedress which is about 1/2 of the application rate used by local farmers. The highest residual soil N0₃-N after harvesting was 24 and 18 and the lowest was 2.6 and 3 mg kg^-1 soil for Bajgah and Kooshkak soils, respectively. When maximum corn grain yield was obtained, chlorophyll meter reading at the middle of leaf blade at dough stage, was 49 for both sites. It seems that N fertilizer application rate by local farmers is excessive.

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Nitrogen is usually the most limiting nutrient for crop production. Manganese deficiency in some calcareous soils of Iran has been reported. The objective of this study was to evaluate the effect of N and Mn on the growth and chemical composition of spinach (Spinacia oleracea L.) under greenhouse conditions. The experiment was conducted in a soil from Chitgar series (Fine-loamy, carbonatic, thermic, Calcixerollic Xerochrepts). Treatments consisted of factorial arrangement of five N rates (0, 50, 100, 200 and 400 mg kg^-1 as NH₄NO₃) and three Mn rates (0, 15 and 30 mg kg^-1 as MnSO₄) in a completely randomized design with four replications. Plants were allowed to grow for 60 days and a hand-held SPAD-502 chlorophyll meter was used to evaluate leaf chlorophyll status at harvest.

 Results showed that N and Mn application increased shoot dry weight, N and Mn concentrations and total uptake, Mn:Fe ratios and chlorophyll readings, significantly. Nitrogen increased concentrations and total uptake of Zn, Cu and total uptake of Fe in plants, but decreased Fe concentration. Addition of Mn decreased Fe and Zn concentrations in spinach but increased total uptake of Fe and Cu. When maximum dry matter was obtained, the chlorophyll meter reading was about 40. A similar study should be carried out under field conditions before the N and Mn fertilizer recommendations for spinach can be made.

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Micronutrients availability including that of Zn is critical for optimum growth of plants. Zinc availability in calcareous soils of Iran is relatively low due to the presence of a large amount of CaCO₃ and high pH levels. Overapplication of phosphorus to soils may also cause P-induced Zn deficiency. The objective of this experiment was to evaluate the effect of phosphorus and zinc application on the growth and chemical composition of corn (Zea mays L.) under greenhouse conditions. Treatments consisted of a factorial combination of 5 levels of P (0, 25, 50, 100 and 200 µg P/g soil as KH₂PO₄) and 3 levels of Zn (0, 5 and 10 µg Zn/g soil as ZnSO₄. 7H₂O) in a completely randomized design with 3 replications. Plants were allowed to grow for 60 days and then cut at the soil surface.

 Results showed that P and Zn applications increased top dry weight. Applied P increased P concentration and total uptake in plants, but decreased Zn concentration and had no effect on Zn uptake. Zinc application decreased P concentration of com but increased Zn uptake and concentration. The P: Zn ratio in plants increased with P application but decreased with Zn addition. Application of P and Zn increased Fe concentration in plant but decreased Mn concentration and had no effect on Cu concentration. Prior to making any fertilizer recommendations, more research is required to precisely evaluate the response of com to P and Zn applications under field conditions.

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Phosphorus (P) and iron (Fe) are essential nutrients for plants. Iron availability is low in calcareous soils of Iran due to the excessive amounts of CaCO₃ and high pH. Overfertilization of P fertilizers may also decrease Fe availability. The objective of this study was to evaluate the effect of P and Fe on the growth and chemical composition of corn (Zea mays L.) under greenhouse conditions. Treatments consisted of a factorial arrangement of P rates (0, 40, 80, 120 and 160 mg kg-1 as KH₂PO₄) and Fe rates (0, 2.5, 5 and 10 mg kg^-1 as Fe EDDHA) in a completely randomized design with four replications. Plants were grown for 8 weeks in a loamy soil, calssified as Chitgar series (fine-loamy, carbonatic, thermic, Typic Calcixerepts). Results showd that P application up to 80 mg kg^-1 increased corn top dry matter. Corn P concentration and total uptake increased by P application but decreased by Fe application. Application of Fe up to 5 mg kg^-1 increased dry matter but decreased it at higher rates. Concentration and total uptake of Fe increased by Fe application but decreased by P application. Zinc and copper concentrations decresed significantly when P was added. Manganese concentration increased at 40 mg P kg^-1 but decreased at higher rates. Iron application decreased zinc and manganese concentrations but had no effect on copper.

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Iron (Fe) availability is low in calcareous soils of Iran due to high pH levels and presence of excessive amounts of CaCO₃. Overfertilization by phosphorus (P) fertilizers may also decrease Fe availability. The objective of this study was to evaluate the effects of P, Fe and their interactions on the growth and chemical composition of soybean [Glycine max (L.) Merrill] under greenhouse conditions. Treatments consisted of a factorial arrangement of P rates (0, 40, 80, 120 and 160 mg kg^-1 as KH₂PO₄) and Fe rates (0, 2.5, 5 and 10 mg kg^-1 as FeEDDHA) in a completely randomized design with four replications. Plants were grown for 8 weeks in a loamy soil, classified as Chitgar series (fine-loamy, carbonatic, thermic, Typic Calcixerepts). Results showed that P application up to 80 and Fe at 2.5 mg kg^-1 increased shoot dry matter. Phosphorus concentration, total uptake and P:Fe ratio in soybean increased by P application but decreased by Fe application. Application of Fe up to 2.5 mg kg^-1 increased dry matter but decreased it at higher rates. Concentration and total uptake of Fe increased by Fe application but decreased by P application. Interaction of P and Fe had no effect on shoot dry matter. Zinc (Zn) and copper (Cu) concentrations decreased significantly when P was added and manganese (Mn) concentration increased up to 40 mg P kg^-1 but decreased at higher rates. Iron application had no effect on soybean Zn and Cu concentrations but decreased Mn concentration at all rates. Prior to any fertilizer recommendations, it is necessary to study the effects of P, Fe and their interactions on soybean under field conditions.

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Twenty-five surface samples of calcareous soils of Fars Province were used to study the distribution of different nitrogen (N) forms to determine the relationship between the N forms and soil charcteristics, and to obtain regression equations for prediction of N forms from soil characteristics. The forms determined were: soil total nitrogen NO₃-N by phenol disulfunic acid NO₃-N extractable by 2 M KCl NH₄-N extractable by 2 M KCl, 1 N sulfuric acid, and 0.25 N sodium hydroxide oxidative released N by acid permanganate and alkaline permanganate and NH₄-N extractable by 2 M KCl at 100 ^oC. The highest amount of N was that released by alkaline permanganate which constituted 4.47% of soil total N and the lowest form was exchangeable NH₄⁺ which amounted to only 0.6% of total N. Water soluble and exchangeable forms accounted for less than 2% of total N. Highly significant correlations were found between total N and acid permanganate-N (r=0.931) and total N and alkaline permanganate-N (r=0.850). Highly significant regression equations were obtained for prediction of soil total N, acid permanganate-N, and alkaline permanganate-N from soil organic matter (OM), which is an indication of a close relationship of these N forms with OM.

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The effect of phosphorus (P) (0, 25, and 50 mg kg-1 soil as Ca(H2PO4)2) and organic matter (OM) (0, and 2% w/w feedlot cattle manure) on P and zinc (Zn) distribution in different parts of wheat plant (Triticum aestivum L.) at various growth stages and its relationship with soil P and Zn were determined in greenhouse condition. In all pots, shoot P concentration decreased as plant growth proceeded. Phosphorus concentration of shoot and flag leaf decreased from 7th to 9th stage of growth, whereas that of spickle increased. Spickle P uptake and Zn uptake of stem, shoot, flag leaf, and spickle increased with proceeding of wheat growth. Phosphorus uptake of shoot increased from 3th to 9th growth stages, whereas P uptake of stem and flag leaf decreased from 7th to 9th growth stages. Soil P and Zn concentrations increased with application of P and OM and plant growth. The trend of P and Zn changes in shoot, stem and flag leaf was similar. It is, therefore, concluded that analyzing flag leaf for P and Zn concentrations be used for prediction of plant nutritional status of those nutrient elements in cases where such information is needed.

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Application of compost and compost leachate as organic fertilizers can improve plant growth, nutrients uptake and increase phytoavailability of nutrients in soil. A factorial experiment (4×4×2) was conducted in a completely randomized design to evaluate the effect of compost and compost leachate on growth and chemical composition of barley and bioavailability of some nutrients in calcareous clay loam soil and sandy soil under greenhouse conditions. Treatments consisted of four levels of compost (0, 15, 30, and 60 g kg-1), four levels of compost leachate (0, 10, 20, and 40 g kg-1), and two culture mediums (clay loam soil and sandy soil) with three replicates. Results indicated that application of compost and compost leachate significantly increased barley shoot dry matter, the number of tillers, spikes and grain yield in clay loam soil and sandy soil. The maximum barley shoots dry matter and numbers of tillers in both culture mediums were obtained at the highest level of compost or compost leachate, and the maximum number of spikes and grain yield were obtained at the lowest level of compost or compost leachate. Application of compost in clay loam soil and sandy soil increased shoot and root concentrations of nitrogen (N), phosphorus (P), Iron (Fe), manganese (Mn), zinc (Zn) and copper (Cu). However, addition of compost leachate only increased shoot concentrations of Fe and P. Increasing compost levels increased post harvest concentrations of NO3- N, P, Fe, Mn, Zn, Cu and also electrical conductivity and organic matter content of clay loam soil and sandy soil. Addition of compost leachate significantly increased concentrations of Fe, Zn, Cu and also electrical conductivity and organic matter content of both culture mediums. In both culture mediums and both compost and compost leachate treatments, post harvest concentrations of micronutrients were above critical levels. Therefore, addition of these nutrients is not required for the next cultivation. Generally, compost and compost leachate are appropriate organic fertilizers for barley production however, high salinity level in compost leachate, the rate and frequency of leachate application, particularly in sand, needs intensive control and monitoring. Prior to any fertilizer recommendation, the results of this study need to be verified under field conditions, as well.

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Contamination of agricultural soils by heavy metals is a serious threat from both agricultural and environmental standpoints. Among heavy metals, cadmium (Cd) toxicity for humans and plants is of great concern due to its high mobility and phytoavailability in soil even at low concentrations. Opposite to Cd, Phosphorus (P) is an essential nutrient for plant growth. A greenhouse experiment was carried out in a completely randomized design to examine the influence of Cd, P and their interaction on the growth and chemical composition of spinach grown on a calcareous soil. Treatments consisted of four Cd levels (5, 10, 20 and 40 mg/kg soil as cadmium sulfate) and four P levels (0, 20, 40 and 80 mg/kg soil as mono-calcium phosphate) in three replicates. The results indicated that 40 mg Cd significantly decreased spinach dry weight by 47% but P application decreased detrimental effect of Cd on spinach dry weight. Also, phosphorus application significantly decreased Cd concentration in spinach aerial parts by 78%. Increasing Cd levels increased concentration of this element in spinach shoots. Addition of 40 mg Cd decreased P concentration by 21.5% in aerial parts. Zinc (Zn), manganese (Mn), calcium (Ca), and nitrogen (N) concentration significantly decreased with P application but increased concentration of sodium (Na). Cadmium application decreased Zn concentration but increased Ca, Na and N concentrations in spinach. Our tentative conclusion is that P application in P-deficient soils is probably effective in decreasing Cd concentration and the detrimental effect of Cd on spinach growth, indicating a negative interaction between these elements. Prior to any fertilizer recommendation, the results of this experiment should be verified under field conditions

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This study was conducted to investigate the effects of poultry manure (PM) and its derived biochars on chemical properties of a sample calcareous soil. Poultry manure and its derived biochars at 200(B₂₀₀), 300(B₃₀₀) and 400(_B400)°C were incorporated with 400 g of soil at 2% level (w/w) and incubated for 150 days. Some chemical properties of soil and bio-availability of some nutritional ingredients such as phosphorous, potassium, iron, manganese, zinc and copper were determined at different times of incubation. Soil nutrients availability, organic carbon (OC), electrical conductivity (EC) and cation exchange capacity (CEC) increased by addition of all these organic substances. Biochars prepared at higher temperatures were more effective in increasing soil OC and its durability. Addition of PM and B₂₀₀ decreased soil pH, whereas B₄₀₀ increased it. Although highest soil EC was observed in B₃₀₀ and B₄₀₀ treated samples in the early stages of incubation, the rate of increasing in soil EC was higher at PM and B₂₀₀ treated samples. In general, it was concluded that biochar prepared at 300°C had the highest effect on availability of nutrients and their durability in the soil. 

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This study was conducted to investigate the effects of poultry manure (PM) and derived biochars on phosphorous (P) availability and apparent recovery in a calcareous soil. Treatments consisted of four rates of P (0, 30, 60 and 90 µgg-1) and five organic substances (blank, poultry manure and derived biochars at 200, 300 and 400°C). organic substances were incorporated with 400 g of soil at 2% level (w/w). All soil treated samples plus control were incubated for 150 days. Soil P availbility determined at 8 different stage of incubation time period. Phosphorous availability was less in untreated soil samples with organic substances and also decreased with time. Although P recovery from inorganic P fertilizer was high in the early stages of incubation time compared to treated soil samples but decreased with time, if not treated with organic substances. Phosphorus availability and recovery increased with time in PM and biochares treated soil samples. Simultanous application of inorganic P and organic substances decreased apparent P recovery. Negative interaction obsorved between organic substances and high rates of inorganic P fertilizer on P availability. It was concluded that PM biochar prepared at 300°C had the highest effect on adjusting P availability in calcareous soil.