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An incubation study was conducted in laboratory to determine the effect of lime (L) as CaCO 3 and phosphorus (P) as TSP on soil pH and available soil P in an acid soil. Four rates of L equivalent to 0, 1, 2 and 3 ton CaCO 3 ha −1 and four rates of P equivalent to 0, 25, 50 and 75 mg P kg −1 were applied in combinations as treatments. The soil was incubated at field capacity for 8 weeks (wk) after which they were extracted using NaHCO 3 (Olsen), Mehlich-3, Kelowna and Bray & Kurtz-1 extractants and soil pH was determined. Lime significantly (P < 0.001) increased soil pH. Phosphorus decreased it, though not significantly. Both L and P had significant effects (P < 0.001) on P availability irrespective of extractants used. Two ton CaCO 3 plus 75 mg P kg −1 gave the highest available phosphorus. Mehlich-3 method extracted the largest amount of P (14.54-67.35 mg•kg −1) while Olsen extracted the smallest amount (3.25-32.77 mg•kg −1). The mean extractable P in soils was found to be in the order of Olsen < Kelowna < Bray & Kurtz-1 < Mehlich-3. Although the four methods extracted different amounts of P from soil, values of P extracted by the different methods were strongly correlated among themselves (R 2 = 0.87 to 0.95).

A pot experiment was carried out to investigate the yield of Indian spinach (Basella alba L.) and their uptake and availability of phosphorus from lime and phosphorus amended acidic soil. Four rates of lime (L) equivalent to 0, 500, 1000 and 2000 kg CaCO 3 ha −1 and four rates of phosphorus (P) equivalent to 0, 50, 100, and 150 kg·P·ha −1 of TSP were applied in combinations as treatments. Dry matter yield, P concentrations in shoot and root and P uptake by Indian spinach were determined after harvesting 10 weeks old plant and soil samples were collected from each pot to measure available P by Olsen method. Both L and P and their combinations had significant (P < 0.001) effects on shoot and root biomass, shoot and root P concentrations, P uptake by Indian spinach and P availability. Although lime and P increased biomass production, P concentrations of shoot and root, and its uptake by Indian spinach and available P, this effect was boosted by combining L with P applied. 1000 kg lime plus 100 kg P were adequate for plant growth. Available P was strongly and positively correlated (R 2 = 0.909, P = 0.000) with P uptake by plant. Results of the present study indicated that lime and phosphorus could be used in combination to enhance plant growth.

A pot experiment was carried out to investigate the comparative effect of city finished compost and NPK fertilizer on the growth and availability of phosphorus to radish (Raphanus sativus L.). An air dried sandy loam soil was mixed with five rates of city finished compost (CFC) equivalent to 0, 5, 10, 20, 40 ton·ha -1 and three rates of NPK fertilizer equivalent to 50% (N-P-K = 69-16-35 kg·ha -1 ), 100% (N-P-K = 137-32-70 kg·ha -1 K) and 150% (N-P-K = 206-48-105 kg·ha -1 ). Four plants were harvested at 45 days of growth and remaining one plant was harvested at 90 days of growth and separated into leaves and bulbs. After harvest, soil samples were collected from each pot to measure soil pH and available P extracted by Olsen, Mehlich-3, Kelowna and Bray & Kurtz-1 extractants. The growth parameters (length of leaves and bulbs, fresh and dry weight of leaves and bulbs), relative dry matter yield, plant P concentrations, P uptake by radish, soil pH, and available P increased by the rates of CFC and NPK fertilizer treatments. Among the treatments, growth performance of radish was better with the highest rate of 40 t·ha -1 CFC treatments. The results obtained from the 5 and 10 t·ha -1 CFC treatment were comparable with the results of 50% and 100% NPK fertilizer treatments respectively. Similar effects of amendments were obtained in the case of plant P concentration, uptake of P by plant, soil pH and available soil P concentration. Available P and soil pH showed very strong and positive correlation (P < 0.001) with dry matter yield, P uptake by plant. The P extracted by various extractants also showed strong positive correlation (r = 0.973 to 0.994; P < 0.001 ) each other indicating the suitability of any of the extractants to predict available P. Results of the present study indicated that 10 t·ha -1 city finished compost could be used instead of 100% to obtain similar yield and to improve soil conditions.

Background: Understanding the morphology of the root system in lentils is critical for the identification of root characteristics for breeding cultivars with enhanced phosphorus use efficiency (PUE) to better adapt to poor P environments. PUE and variability in root morphological characteristics at the early vegetative stage were investigated among 40 indigenous and exotic lentil genotypes in a hydroponic phenotyping system.Results: A prerequisite for developing P-efficient crop cultivars is to categorise existing germplasm. In this experiment, 40 lentil genotypes were grown for 24 days under P deficit (3 μm KH2PO4) and P adequate (250 μm KH2PO4) conditions in hydroponics. Lentil genotypes exhibited significant variability for root, biomass, and P efficiency traits. Different techniques have identified various genotypes of lentils based on the efficiency of phosphorus uptake (PUPE) and the efficiency of phosphorus utilization (PUTE). IG 568229 showed the highest PUPE, while the wild ILWL-15 lentil showed the lowest PUPE in both media. The wild lentil ILWL-95 showed maximum PUTE under P adequate medium. The IC 560135, IG 334, IG 560157 and IG 568229 genotypes were found to be highly efficient at both P levels and to be ideal for a large range of P levels without having a drastic impact on biomass output.Conclusions: The primary step for breeding more P-efficient crop plants is the classification of the germplasm. IC 560135 and IC 268238 contrasting lentil lines may be useful for mapping population development, mapping and tagging of gene(s), QTLs for PUE in lentil. These efficient P crops also ensure food and nutritional security, in addition to reducing the cost of cultivation.