RESPONSE OF MAIZE AND ASSOCIATED WEEDS TO IRRIGATION INTERVALS, WEED MANAGEMENT AND NITROGEN FORMS

Abstract

Two field experiments were conducted during the 2005 and 2006 growing seasons at the Experimental Farm of the National Research Centre at Shalakan, Kalubia Governorate, Egypt, to study the response of maize yield and its components and associated weeds to two irrigation intervals (every 2 and 3 weeks), three weed management treatments (metribuzin herbicide, hoeing twice at 25 and 40 days from sowing and weedy check) and four N forms (ammonium sulfate, ammonium nitrate, urea and calcium nitrate). Results showed that irrigation every 2 weeks significantly decreased grassy and total weeds and NK uptake by weeds. Providing maize plants by irrigation every 2 weeks significantly increased chlorophyll a leaf content, yield and its components, grain P content and protein yield/fed. Hoeing twice was more effective than metribuzin herbicide for controlling grassy and total weeds and lowering N, P and K uptake by weeds. Application of metribuzin markedly increased chlorophyll a leaf content, while hoeing twice was the effective treatment for increasing yield and its components, except ear diameter, and enhanced grain N content, protein % and protein yield/fed. Calcium nitrate significantly decreased dry weight of grassy and total weeds and NK uptake by weeds. Adding ammonium nitrate markedly increased chlorophyll a leaf content, number of rows/ear, 100-kernel weight and grain yield/fed. Irrigation every 2 weeks with metribuzin treatment gave the maximum values of 100-kernel weight, ear yield and grain yield /fed when ammonium nitrate as nitrogen form was used.