Phosphorus Rates on Growth Parameters of Maize (Zea mays L.) in Reddish Brown Earth under Greenhouse Condition

Phosphorus is an essential element for plants. However, many soils lack sufficient in formthat is readily available to crops to ensure optimum growth especially in dry zone soils in SriLanka. Hence, this study was undertaken with the objective of evaluating the impact ofdifferent rates of Triple Super Phosphate (TSP) as a source of Phosphorus for maize (Var.Sampath) growth under greenhouse condition. Top soils at a depth of 0-25 cm were collectedfrom research farm, Puliyankulama and from a farmland in Kahatagasdigiliya, Anuradhapuradistrict. Greenhouse experiment conducted for both soils. Twenty pots were arranged in acompletely randomized design with four treatments (0, 20, 30 and 40 kg of Phosphorus ha-1)and five replicates for a single experiment. Soil samples were taken at 4, 8, 10, 12 and 16weeks after planting (WAP). The soil samples were analysed for soil pH, electricalconductivity (EC) and available Phosphorus (Olsen’s method). The leaf Phosphorus contentat 50% tasseling stage was measured using dry ash method. The growth parameters wereplant heights at 4, 8, 10 and 12 WAP, number of days to 50% tasseling and number of days to80% silking. Results indicate soil pH, EC, and leaf Phosphorus % are not significantlydifferent (p<0.05) at different levels of Phosphorus in both locations. However, soil availablePhosphorus is significantly different (p<0.05) to the control. Conversely it does not showsignificant different (p<0.05) among fertilized treatments at both sites. Moreover, plant heightat 50% tasseling stage, number of days to 50% tasseling and number of days to 80% silkingare not significantly different (p<0.05) among any treatments at both soil types. Hence, theresults further revealed that the different levels of P treatments have no significant effect onsoil pH, EC, available P, leaf P and growth parameters of maize variety Sampath undergreenhouse conditions.

Estimation of Optimum Available Phosphorous Extraction Methods for Reddish Brown Earth Soil

Several extraction methods are used to determine plant available Phosphorus (P) that affectfor growth and yield of plants. This study was conducted to evaluate the different available Pextraction methods for reddish brown earth (RBE) soil in dry zone of Sri Lanka. Theexperiment was conducted as a randomised complete block design (RCBD) with fourreplicates at Kahatagasdigiliya in Anuradhapura district during Maha (2013/2014) season.Seven extraction methods, i.e., Olsen‟s, Bray 1, Borax, Mehlich III, Modified Kelowna,ammonium chloride and distilled water were tested. Soil samples were collected at thetasseling stage of maize plants (Zea mays L.) treated with four fertiliser rates: 0 (T1), 20 (T2),30 (T3) and 40 (T4) kg of P ha-1. Soil samples were analysed for pH, available P and total Papart the initial chemical characterisation. The effect of extraction methods for soil availableP and the P recovery, interactions among the P levels with different extraction methods wereevaluated. Available P extraction and P recovery using Modified Kelowna method wassignificantly greater than other methods (p<0.05). Olsen‟s, Bray 1, Borax, Mehlich III,Ammonium Chloride extraction methods were not significantly different (p>0.05) inavailable P determination. The extraction methods and fertiliser levels were significantlydifferent (p<0.05) with soil available P. The P extraction in T4 was comparatively higher thanother methods except distilled water extraction. Modified Kelowna method was mostappropriate in available P extraction under experimental conditions in RBE soil.Keywords: Phosphorus, P extraction methods, P recovery, RB