STUDIES INTO ENHANCING PRODUCTIVITY OF HYBRID MAIZE (zea mays L.) UNDER VARIOUS AGRO - MANAGEMENT PRACTICES

Abstract

The research entitled “studies into enhancing productivity of hybrid maize (Zea mays L.) under various agro-management practices” was sown at Post Graduate Agricultural Research Station, University of Agriculture, Faisalabad in two sets of field trials during Kharif 2005 and 2006. First experiment comprised of three levels of nitrogen viz. 150, 200 and 250 kg ha -1 and six duration of weed-crop competition i.e., 0 (weed free control), 2, 3, 4, 5 or 15 weeks (weedy check), then plots were maintained weed free till harvest. The second experiment, “utilization of allelopathy for reducing herbicide dose in maize sown at different plant densities” comprised of three plant densities (98765, 65884, and 49383 plants ha -1 ) and five weed control methods. Weed control methods were weedy check, Primextra gold 720 SC (atrazine 320 g L -1 + s-metalochlor 400 g L -1 ) at 1440 g a.i. ha -1 as pre-emergence, hand hoeing twice (20 and 40 DAS), one hand hoeing + earthing up (20 and 40 DAS respectively), Primextra gold 720 SC (atrazine 320 g L -1 + s- metalochlor 400 g L -1 ) at 720 g a.i. ha -1 (50 % reduced dose) + sorghum (Sorghum bicolor L.) and sunflower (Helianthus annuus L.) water extracts each at 15 L ha -1 as pre- emergence. In both the experiments, the crop was sown on 67.5 cm spaced ridges in plots measuring 2.7m x7.0 m with the help of dibbler during 1 st . week of August. The results of the experiments in brief are: In first experiment, nitrogen levels from 150-250 kg ha -1 increased total weed density up to 26 % while their fresh weight 35% and that of weed dry weight up to 33%. Crop maturity was delayed by 3 days. Yield contributing factors like plant height (9%), kernel weight per cob (9-12%), 1000 kernel weight (4%), and thus final kernel yield (26%) was also enhanced with the higher doses of fertilizer-nitrogen. Therefore, for as the competition durations were concerned, they had positive effect on weed dynamics but negative effect on crop meaning thereby that more the weed crop competition duration lower the crop yield due to poor growth and yield contributing factors. Although the increased durations of weed crop competition resulted in yield losses, however, these losses were maximum (67%) in plots which received lower quantities of nitrogen (150 kg ha -1 ) and maximum weed crop competition i.e., 105 days (up to crop maturity) which indicated that more intensive weed management system is required under low fertility levels. It is pertinent to mention that the presence of weeds had minimum effect on crop growth at initial stages provided it is supplied with sufficient amounts of available 1nutrients like application of nitrogen at 250 kg ha -1 . Nitrogen levels had positive impact on quality of kernel (oil, protein, and starch) while duration of weed-crop competition had negative effect on quality of kernel. In second experiment, there was negative correlation between the densities of maize and weeds. The maize crop sown at density of 98765 plants ha -1 reduced the weeds per unit area (weed density) to the extent of 20% (40 DAS) and 24% (105 DAS). Similarly, the reduction in dry weight was 26% (40 DAS) and 20% (105 DAS). Maximum LAI (7.95), LAD (418 days), and CGR (23.69) were recorded under higher plant densities. Although the kernel weight per cob (79.96 g) and thousand kernel weight (242.93 g) were reduced when the crop was planted at higher densities but the final kernel yield was maximum (7.17 t ha -1 ). The best weed control method was one hoeing (20 DAS) in combination with earthing up (40 DAS), but application of reduced dose (50 %) of atrazine + S-metalochlor at 720 g a.i. ha -1 (half of label dose) in combination with sorghum + sunflower water extracts each at 15 L ha -1 proved to be economical as its MRR (3424 %) was maximum.