An incubation experiment was conducted to study the effects of farmyard manure (FYM) and elemental sulfur (S) on availability, fractionation and transformation of phosphorus in calcareous sandy soil. Soil samples were treated with FYM at levels: 0 (FYM0), 2.5 (FYM1), 5 (FYM2) and 7.5 (FYM3) g pot−1 and S at levels: 0 (S0), 0.1 (S1), 0.2 (S2) and 0.3 (S3) g pot−1. The soil was incubated for ten weeks under field capacity conditions. Additions of FYM caused significant increases in the amount of available P (Olsen−P) from 34.57 to 44.54 mg kg−1. The S with FYM application significantly increased Olsen−P of this soil at S1FYM1 from 42.95 to 52.70 mg kg−1. Significant reduction in Olsen−P was observed at S2 and S3 levels, but the addition of S at S1 level led to its insignificant increase. FYM application transformed HCl-Pi, NaOH II-Pi and residual P to NH4Cl-P, NaHCO3-Pi, NaHCO3-Po, NaOH I-Pi, NaOH I-Po and NaOH II-Po fractions. Application of S converted the NH4Cl-P, NaOH I-Pi and HCl-Pi fractions to NaHCO3-Pi, NaHCO3-Po, NaOH I-Po, NaOH II-Pi, NaOH II-Po and residual P fractions. It’s recommended adding FYM to calcareous sandy soils as well as adding S combined with FYM to improve the soil properties.

NULLGroundwater is considered an important water source for agricultural, drinking and domestic uses in many regions of the world including Libya, especially in its coastal area. This study aims to assess the quality of groundwater in north-western area of Libya for drinking and agricultural through examining its physico-chemical characteristics such as pH, electrical conductivity (EC), total dissolved solids (TDS), total hardness, cations and anions. These parameters are used to assess the suitability of groundwater for domestic purposes by comparing their current values with the maximum permissible limits of these parameters that are recommended by World Health Organization (WHO). The EC, sodium adsorption ratio, soluble sodium percentage, Kelly’s ratio and magnesium adsorption ratio of the groundwater are also used to evaluate its suitability for irrigation. Gibbs diagram shows the evaporation–crystallization dominance in controlling the quality of groundwater. The main hydrochemical facies is Ca–Mg–SO4–Cl type of water in both methods of Piper and Chadha’s diagram. The results revealed that most groundwater samples were not suitable for drinking and household uses due to their high levels of most cations and anions, total hardness, EC and TDS. Most of the collected water samples showed the investigated parameter levels exceeded the permissible limits of WHO. Therefore, most of the groundwater samples are considered unsuitable for irrigation due to its high salt content, unless certain measures for salinity control are undertaken.

NULLAssessment and understanding of soil available phosphorus (P) and potassium (K) content distribution is an important part of deciding whether or not the fertilization is appropriate or even necessary for a soil. So, the main objective of this study is to evaluate and map the spatial variability of the available soil P and K using the geostatistical technique. Georeferencing surface soil samples (0-25 cm) were collected from four sites representing course-textured soils in El- Kharga and El-Dakhla oases. Ordinary Kriging (OK) technique was applied for the spatial interpolation of available soil P and K contents. The spatial distribution of available P and K was analyzed and mapped by Arc GIS (version 10.2.2). The results showed that concentrations of the available soil P and K ranged from 0.35 to 85.02 mg/kg and from 11 to 6204 mg/kg, respectively. The nugget-to-sill ratio suggested a strong spatial dependence for both available soil P and K in all sites of the study area, indicating that the available soil P and K were mainly controlled by intrinsic factors. The interpolation models varied for both P and K as well as from site to another site across the study area. Cross-validation proved that the chosen models were the best fitted semivariogram models to map spatial distribution of the available soil P and K. The produced maps of spatial distributions for soil P and K availability were characterized by high accuracy. So, site specific management can be planned and considered to be applied for this study area. Also, these maps can facilitate and help in making decisions for choose appropriate fertilization policies for these soils as well as to avoid adding fertilizers for sites which do not need to be fertilized. Our results confirmed that the integration of statistics, geostatistics and GIS provides a powerful tool to assess, describe and map the spatial variability of the available soil phosphorus and potassium. As well as to develop high resolution maps that may aid variable rate management (e.g. fertilization).

NULLAssessment and understanding of soil available phosphorus (P) and potassium (K) content distribution is an important part of deciding whether or not the fertilization is appropriate or even necessary for a soil. So, the main objective of this study is to evaluate and map the spatial variability of the available soil P and K using the geostatistical technique. Georeferencing surface soil samples (0-25 cm) were collected from four sites representing course-textured soils in El- Kharga and El-Dakhla oases. Ordinary Kriging (OK) technique was applied for the spatial interpolation of available soil P and K contents. The spatial distribution of available P and K was analyzed and mapped by Arc GIS (version 10.2.2). The results showed that concentrations of the available soil P and K ranged from 0.35 to 85.02 mg/kg and from 11 to 6204 mg/kg, respectively. The nugget-to-sill ratio suggested a strong spatial dependence for both available soil P and K in all sites of the study area, indicating that the available soil P and K were mainly controlled by intrinsic factors. The interpolation models varied for both P and K as well as from site to another site across the study area. Cross-validation proved that the chosen models were the best fitted semivariogram models to map spatial distribution of the available soil P and K. The produced maps of spatial distributions for soil P and K availability were characterized by high accuracy. So, site specific management can be planned and considered to be applied for this study area. Also, these maps can facilitate and help in making decisions for choose appropriate fertilization policies for these soils as well as to avoid adding fertilizers for sites which do not need to be fertilized. Our results confirmed that the integration of statistics, geostatistics and GIS provides a powerful tool to assess, describe and map the spatial variability of the available soil phosphorus and potassium. As well as to develop high resolution maps that may aid variable rate management (e.g. fertilization).

NULLAssessment and understanding of soil available phosphorus (P) and potassium (K) content distribution is an important part of deciding whether or not the fertilization is appropriate or even necessary for a soil. So, the main objective of this study is to evaluate and map the spatial variability of the available soil P and K using the geostatistical technique. Georeferencing surface soil samples (0-25 cm) were collected from four sites representing course-textured soils in El- Kharga and El-Dakhla oases. Ordinary Kriging (OK) technique was applied for the spatial interpolation of available soil P and K contents. The spatial distribution of available P and K was analyzed and mapped by Arc GIS (version 10.2.2). The results showed that concentrations of the available soil P and K ranged from 0.35 to 85.02 mg/kg and from 11 to 6204 mg/kg, respectively. The nugget-to-sill ratio suggested a strong spatial dependence for both available soil P and K in all sites of the study area, indicating that the available soil P and K were mainly controlled by intrinsic factors. The interpolation models varied for both P and K as well as from site to another site across the study area. Cross-validation proved that the chosen models were the best fitted semivariogram models to map spatial distribution of the available soil P and K. The produced maps of spatial distributions for soil P and K availability were characterized by high accuracy. So, site specific management can be planned and considered to be applied for this study area. Also, these maps can facilitate and help in making decisions for choose appropriate fertilization policies for these soils as well as to avoid adding fertilizers for sites which do not need to be fertilized. Our results confirmed that the integration of statistics, geostatistics and GIS provides a powerful tool to assess, describe and map the spatial variability of the available soil phosphorus and potassium. As well as to develop high resolution maps that may aid variable rate management (e.g. fertilization).

NULLAssessment and understanding of soil available phosphorus (P) and potassium (K) content distribution is an important part of deciding whether or not the fertilization is appropriate or even necessary for a soil. So, the main objective of this study is to evaluate and map the spatial variability of the available soil P and K using the geostatistical technique. Georeferencing surface soil samples (0-25 cm) were collected from four sites representing course-textured soils in El- Kharga and El-Dakhla oases. Ordinary Kriging (OK) technique was applied for the spatial interpolation of available soil P and K contents. The spatial distribution of available P and K was analyzed and mapped by Arc GIS (version 10.2.2). The results showed that concentrations of the available soil P and K ranged from 0.35 to 85.02 mg/kg and from 11 to 6204 mg/kg, respectively. The nugget-to-sill ratio suggested a strong spatial dependence for both available soil P and K in all sites of the study area, indicating that the available soil P and K were mainly controlled by intrinsic factors. The interpolation models varied for both P and K as well as from site to another site across the study area. Cross-validation proved that the chosen models were the best fitted semivariogram models to map spatial distribution of the available soil P and K. The produced maps of spatial distributions for soil P and K availability were characterized by high accuracy. So, site specific management can be planned and considered to be applied for this study area. Also, these maps can facilitate and help in making decisions for choose appropriate fertilization policies for these soils as well as to avoid adding fertilizers for sites which do not need to be fertilized. Our results confirmed that the integration of statistics, geostatistics and GIS provides a powerful tool to assess, describe and map the spatial variability of the available soil phosphorus and potassium. As well as to develop high resolution maps that may aid variable rate management (e.g. fertilization).

Land suitability analysis can help to achieve sustainable crop production with a proper use of the natural resources. The current study was carried out on the soils of north-western area of Libya to assess their morphological, physical and chemical properties and their suitability for growing irrigated crops. The studied area lies between latitudes 32° 30′ 00.9" and 32° 57′ 34.2'' N and between longitudes 11° 35′ 08.4" and 11° 45′ 09.2" E. Two suitability methods (Sys &Verhey and Storie methods) were used to assess the land suitability of this area. According to Sys and Verhye method, the soils of the studied area varied in the suitability for irrigation between highly suitable (S1) to marginally suitable (S3). However, according to modified Storie index method the soils productivity, ranged from excellent (grade 1) for agriculture to non-agricultural (grade 6). The modified Storie index method was more effective in assessing the land suitability of this area. The drip irrigation system was also more suitable than surface irrigation method for most of the soils of the studied area. The indeces of soil suitability rating and percentage for growing alfalfa, sorghum, barley, maize, millets, wheat and safflower were higher compared to those for growing soybean, sunflower and sesame. Onion and green pepper crops were moderately suitable to be grown in 42% of the soils of the studied area while the other vegetables were not suitable to be grown in most of the soils of the studied area. The evaluated fruit trees could be arranged according to the soil suitability rating and percentage in the order of date palm > olives > guava > citrus > banana. The results also revealed that the studied area has a good potential to produce the selected crops under irrigation provided that the water requirements for these crops are met. The main limiting factors for land suitability for growing crops are soil texture, soil depth, calcium carbonate, alkaline pH and soil salinity.

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This study was carried out to calculate response of two cultivars of wheat which represent the hexaploid and tetraploid species to different cropping sequences and nutrient rates of NPK. This study was carried out in the Experimental Farm of Faculty of Agriculture, Assiut University in the two growing seasons of 2004/2005 and 2005/2006 seasons. Two cropping systems were studied, i.e. corn – clover – wheat and corn – fallow – wheat. The cultivars studied were Sakha 93& Beni-suef 1 in 2004/2005 and Sids 1 & Beni-suef 1 in 2005/2006 season. The nutrient rates of NPK (kg/fed.) were 80, 15 and 50, i.e. the recommended rates, 40, 7.5 and 25 kg/fed. of NPK, 20, 3.75 and 12.5 kg/fed. NPK and without nutrients. The variables studied were distributed in a split-split plot design in which crop sequence was allotted in the main plots. The cultivars were in split plot whereas the nutrients were distributed in the sub-sub plots. The results obtained in this study could be summarized as follows: 1- The growth parameters such as plant height, leaf area index, number of tillers/plant and total dry matter/plant were improved by planting wheat after clover as compared with the cropping system of corn-fallow-wheat. Cultivars belong to the hexaploid cultivars were characterized by favorite growth parameters as compared with simolina cultivar. The recommended nutrients of NPK favored the growth attributes. 2- Average interval from planting to 50% heading tended to be increased significantly when planting wheat was after clover. No significant differences in earliness among the two cultivars studied were detected. The consistent increase in nutrient rates prolonged the interval to 50% heading. 3- Yield components such as number of tillers/plant at harvest spike length, number of spikelets/spike, and seed index tended to be increased when wheat planting was after clover as compared with the sequence of corn-fallow-wheat. Wheat yield components of hexaploid cultivars, i.e. bread wheat surpassed the semolina cultivar in all attributes except the seed index. The later took the contradict trend in this respect. Linear increases in all yield components were observed as nutrients rates were increased. 4- Average grain yield/fed of wheat was increased significantly when wheat was grown after clover compared with cultivating it after fallow. This is true in the two growing seasons. No significant difference among the cultivars studied was observed. Grain yield per unit area tended to be increased as nutrient rates were increased. Here too, the first order interaction of intensification x fertilization revealed that the cropping sequence of corn-clover-wheat increased the response of grain yield to the recommended rates of NPK compared with the sequence of corn-fallow-wheat. 5- Straw yield/fed was reacted significantly to the cropping sequence practiced in favor of planting wheat after clover. Hexaploid cultivars were superior in straw yield production per unit area compared with tetraploid cultivar. Average straw yield was increased significantly as nutrient rates were increased up to the recommended rates. 6- The biological yield/fed was influenced significantly by cropping systems studied in favor of the cropping sequence of corn-clover-wheat in the two growing seasons. The bread cultivars produced heavier weight of biological yield than semolina cultivar. This relation was significant in the two growing seasons. Consistent increase in biological yield/fed was achieved as nutrient rates increased. 7- Harvest index did not show any definite response to intensification system. Here, semolina cultivar improved harvest index as compared to bread cultivars. Negative trend was noted between harvest index and nutrient rates. This means that harvest index tended to be increased as nutrient rates was decreased. 8- Here it should be noted that the average yield of clover produced from the cropping sequence of corn - temporary clover - wheat was ranged from 8781.82 to 10650 kg/fed. in 2004/2005 season. In 2005/2006 it ranged from 12109.09 to 17318.18 kg/fed.