Stevia Leaf biomass yield PUE P requirement Critical P content Knowledge of phosphorus (P) uptake and its use efficiency by crop plants is essential for adequate management of the plant nutrients to sustain food production with a minimal environmental impact. To study the effects of P on the growth, leaf biomass production, P content and uptake and to estimate P use efficiency (PUE), minimum P requirement and critical leaf P content of stevia, a pot experiment was conducted in the net house of the Department of Agricultural Chemistry, Bangladesh Agricultural University following completely randomized design (CRD) with three replications in acid and non-calcareous soils of Bangladesh. The applied treatments was six viz. 0 (P0), 25 (P25), 50 (P50), 75 (P75), 100 (P100) and 150 (P150) kg P ha-1. Plant samples were collected at 15 days interval to obtain different parameters. Collective results indicated that significantly highest values of different parameters were obtained with P @ 100 kg ha-1 and the lowest from P control. Phosphorus application increased leaf dry yield at harvest by 55 to 510% in acid soil and 70 to 488% in non-calcareous soil over control. The rapid growth of the plant was recorded at the later stages (30 to 60 days after planting). Phosphorus content and uptake was directly proportional with the increased levels of P except the treatment P150 in both soils. Maximum PUE and fertilizer P use efficiency (FPUE) was observed at P100 treatment. Critical P content was estimated to be ca 0.19 and 0.30% in the leaves of stevia plants grown in acid and non-calcareous soils, respectively. For maximum leaf biomass production of stevia grown in acid and non-calcareous soils, the minimum requirement of P was also estimated to be ca 109 and 104 kg ha-1 , respectively. The information of this finding would contribute to optimize the soil P use and improve fertilizer management for stevia cultivation. To cite this article: Maniruzzaman M, T Chowdhury, MAH Chowdhury and MA Rahman, 2017. Phosphorus use efficiency and critical P content of stevia grown in acid and non-calcareous soils of Bangladesh. Res. Agric. Livest., Fish., 4 (2): 55-68. Maniruzzaman et al. Phosphorus use efficiency and critical P content of stevia Res.

Phosphorus (P) deficiency is invariably a common crop growth and yield-limiting factor in unfertilized soils, especially soils high in calcium carbonate, which reduces P solubility. Even when such soils are fertilized, adsorption and desorption lead towards a reversion to stable and less soluble P forms, thus reducing fertilizer use efficiency. Field trials that examine the implications of such P reactions and residual fertilizer P responses in the field are relatively rare in Mediterranean environments. A 5-year field experiment in southern Turkey examined the residual effects of repeated P fertilizer applications for corn production in a calcareous soil Typic Xerofluvent. Following the initial year's fertilization (0, 33, 66 and 99 kg P ha À1 ) to establish a range of soil P levels in subsequent years, the main plots received 0, 9, 18, 27 and 36 kg P ha À1 annually. Grain P uptake was calculated for each year and used in the prediction of P recovery. All plots were sampled and analyzed for available P prior to planting with a local corn hybrid. Soil P values increased with the initial P levels (8-24 mg kg À1 ) but declined after 3 years (6-10 mg kg À1 ). Only the lowest annual P application rate (9 kg P ha À1 ) produced an available P level that was not in the sufficiency range. Grain yields across the main and subplots and years ranged from 6.6 to 13.2 t ha À1 . Overall corn yield averaged over the years increased by 8-33% compared to the control as the rates of applied P increased. However, P application had no effect in a year when below-average rainfall restricted crop growth. A residual P effect on grain yield occurred with higher P application levels in the last year. Leaf and grain P concentrations were in the sufficiency range in general. Grain P uptake was calculated for each year and used in the prediction of P recovery. Actual recovery was higher with low P application rates and ranged between 10.8 and 46.4%. The study indicated that under irrigated conditions, corn is likely to respond to P fertilization, but that buildup of available P can occur within a few years and adequate plant available P levels can be maintained by modest P fertilizer application rates.

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In the Mediterranean region, much emphasis is placed on the role of fertilizers in enhancing crop production to achieve food security. Given the complex nature of phosphorus (P) reactions in soils, considerable research has dealt with fertilizer aspects related to efficient P use, but comparatively less emphasis has been given to plant variation with respect to P efficiency. In this study, selection and adaptation of P-efficient corn genotypes was seen as one possible approach to enhancing P efficiency. Thus, a greenhouse experiment with 10 corn genotypes (traditional to modern), five P application rates (0-200 mg kg 21 ), and four field trials with three genotypes for 2 years were carried out on various calcareous soils (Vertic Torrifluvent, Vertic Calciorthid, Entic Chromoxerert, and Typic Xerofluvent). Measurements were made of root characteristics. Treatments in the field trials were five P application rates as main plots (0-68 P ha 21 ) and three corn genotypes as subplots. Genotypes were selected for the field trials from the greenhouse experiment as ''efficientresponsive,'' ''efficient-nonresponsive,'' and ''inefficient-responsive.'' Dry-matter (DM) yield and plant P uptake by plants increased with P application rates in the greenhouse experiment. Root length and mass were considerably increased by increasing P levels. Genotypes were classified for P efficiency. The studies indicated that because corn genotypes respond to P-fertilizer application differently, this trait could be utilized to exploit native and applied P more efficiently, especially at low levels of available P and when P-fertilizer use is limited. This differential response derives from morphological, physiological, and genetic variability among the genotypes. Although genotypic efficiency is important for fertilizer management, the contribution of the efficiency is not a substitute for fertilizers, especially if high yields are required. Nevertheless, breeding for P-use efficiency should be a component of any program to improve crop yield potential.

Vermicompost products have gained a great importance in plant nutrition over the years. They are reported to have plant growth promoting effects both in horticulture and field crops. The nutritional value and chemical properties of vermicomposts highly depend on the feedstock used in their production. The aim of this study was to evaluate vermicompost manure, derived from the mixture of cattle manure and kitchen scraps, on seed germination and growth of tomato seedlings (Lycopersicon lycopersicum Mill.). Four solid vermicompost amendment rates of 0, 10, 20, and 30% were applied in plastic trays. Vermicompost application delayed and reduced seed emergence in all application rates, while in general, vermicompost substitution promoted growth tomato seedlings up to 20% of application rate. The results showed that vermicompost substitutions greater than 20% had adverse effects on seedling emergence and seedling growth parameters, which was attributed to high EC of vermicompost induced by cattle manure. Results suggest that both physical and chemical properties of the feedstock used for vermicompost production should be taken into consideration in order to sustain high vermicompost quality to ensure targeted plant growth for horticultural and agricultural purposes.