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Pak. J. Bot., 47(SI): 251-254, 2015. |
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Updated: 31-12-15 | ||||
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EFFECT OF WEEDS AND SOIL AMENDMENTS ON N, P AND K CONTENTS OF RICE
NIGHAT SANA, ARSHAD JAVAID*, AMNA SHOAIB AND RUKHSANA BAJWA
Institute of Agricultural Sciences, University of Punjab, Quaid -e-Azam Campus, Lahore 54590, Pakistan *Corresponding author’s email: arshadjpk@yahoo.com, arshad.iags@pu.edu.pk
Abstract: A field experiment was conducted to assess the nitrogen (N), phosphorus (P) and potassium (K) contents of rice (Oryza sativa L.) as influenced by soil amendments and four common weeds namely Echinochloa colonum (L.) Link, Cyperus rotundus L., Marsilea minuta L. and Paspalum paspaloides (Michx.) Scribn. The field soil was amended either with recommended (N) or half dose (½ N) of N-fertilizer as urea along with recommended dose of P2O5 and K2O or with farmyard manure (FYM) @ 15 tons ha-1. N, P and K contents and grain yield were greatly affected by weed competition and soil amendments. The highest N and P contents were recorded in weed free control in recommended dosage of N. N contents in rice were significantly reduced by all the weeds in ½N dose, and by M. minuta and mixed weeds in recommended dose of N. In FYM, all the weeds except E. colonum significantly reduced N contents in rice. P contents were only significantly reduced in ½N dose due to mixed weeds. K contents were significantly enhanced due to presence of weeds in ½N, and were insignificantly affected in FYM amendment. Grain yield was invariably reduced due to weed competition in all the three soil amendments. Mixed weeds proved more damaging than individual weeds. The highest yield losses of 37-75% due to weeds were recorded in FYM followed by 12-56% in ½N dose and 12-40% in recommended N dose treatment. There was a positive correlation between grain yield, and shoot N and P contents, in all the three soil amendments. Correlation between grain yield and shoot K contents was negative in ½N dose and FYM amendments.
Key words: NPK contents, Rice, Soil amendments, Weeds.
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