Some Characteristics of Soils of the Experimental and Research Station at Deirab

Analyses of profile samples from different locations at Deirab reveal that, on the main, the soils are medium-to light-textured and highly calcareous. CaCO3 is found to highly dominate the coarse fraction in the sandy samples, but becomes a significant component of the finer fraction in relatively heavy textured samples. Moisture characteristics of the soils, revealing patterns of their moisture depletion, indicate that in Deirab, crops may incur temporary wilting failing frequent irrigation. Deirab soils are low in CEC. This property is found to correlate significantly (r = 0.71) with the soil clay content. By employing the regression equation, a pure clay separate is calculated to have a CEC of about 30 meq/100g. This value is intermediate between the CEC of chlorite group of minerals and that of attapulgite found by x-ray distraction to be the dominant clay minerals in Deirab soils

Nutrition, dry matter accumulation and partitioning and phosphorus use efficiency of potato grown at different phosphorus levels in nutrient solution

High rates of phosphate fertilizers are applied to potato (Solanum tuberosum L.), which may cause antagonistic interactions with other nutrients and limit crop yields when over-supplied. The purpose of this study was to evaluate the influence of phosphorus (P) levels in nutrient solution on P use efficiency, nutritional status and dry matter (DM) accumulation and partitioning of potato plants cv. Ágata. The experiment was carried out in a greenhouse, arranged in a completely randomized block design with four replications. Treatments consisted of seven P levels in nutrient solution (0, 2, 4, 8, 16, 31, and 48 mg L-1). Plants were harvested after 28 days of growth in nutrient solution, and separated in roots, stems and leaves for evaluations. The treatment effects were analyzed by regression analysis. Phosphorus levels of up to 8 mg L-1 increased the root and shoot DM accumulation, but drastically decreased the root/shoot ratio of potato cv. Ágata. Higher P availability increased P concentration, accumulation and absorption efficiency, but decreased P use efficiency. Higher P levels increased the N, P, Mg, Fe, and Mn concentrations in roots considerably and decreased K, S, Cu, and Zn concentrations. In shoot biomass, N, P, K, and Ca concentrations were significantly increased by P applied in solution, unlike Mg and Cu concentrations. Although higher P levels (> 8 mg L-1) in nutrient solution increased P concentration, accumulation and absorption efficiency, the DM accumulation and partitioning of potato cv. Ágata were not affected