Development Of Management Options For Optimizing Water And Nitrogen Utilization For Maize Production In Malawi

EXTENDED ABSTRACT

Nitrogen and water management practices are key components in Crop production. Plants cannot grow in soil without water, so too when soil is saturated with water. Plants lacking N show stunted growth and yellowish leaves. Too much N can have negative environmental impacts such as contamination of water, pollution, and eutrophication. Leaching is the main vehicle through which applied nitrogen can contaminate groundwater. Identifying the most economic application rate of N fertilizer is most important in high N demanding crops such as maize. Understanding of N movement through soil profile is also essential for more N efficient and minimizing N leaching. The aims of this study were to evaluate the agronomic response of maize to different water and N application regimes; to determine the lateral and vertical movement of nitrogen under different irrigation regimes; and to model the distribution pattern of nitrogen in the maize root zone. The research study was conducted in two irrigation growing seasons from 1st June to 8th September 2012, and from 10th September to 15th December, 2012 at Nkango Irrigation Scheme in Kasungu, Malawi. The factors under study were water and nitrogen with four levels each. A V-notch flume was used to measure volume of applied water to the plots. Triscan Sensor (EnviroScan, Sentek Pty Ltd, Stepney, Australia), which has ability to monitor the direction and movement of nitrogen in the soil at instant time of inserting monitoring probe in the soil, was used to measure total nitrogen concentration at lateral distances. The measurement of the sensor is in Volumetric Ion Concentration (VIC), but using standazation equation the concentration of total nitrogen on each point was calculated. The lateral distances at which measurements were taken were at point of iii application (represented by 0 cm), at 5 cm away from the plant (represented by -5 cm), at 5 cm towards the plant, 10 cm towards the plant (this point was maize planting station), and 15 cm (this point was 5 cm after planting station in the direction opposite from where N was applied). The lateral distances were taken based on spreading and elongation pattern of lateral roots of maize plants. The lateral readings of nitrogen were respecively taken at five soil depths of 20, 40, 60, 80, and 100 cm. The R version 3.2.2, open source statistical software (R Core Team, 2015) was used to run ANOVA statistical analysis on yield data, separate treatment effect means and plot various graphical plots such as box and whisker and interaction effects. The following conclusions were drawn from the study:  The study has concluded that statistically interactive effect of 60% of FWRR and 92 N Kg/ha gave optimum yields compared to other combination of treatments. The interactive effect of nitrogen and water on maize yield has indicated that it is only a combination of 100% FWRR: 92 Kgs N/Ha – 60% FWRR: 92 Kgs N/Ha that has no significant difference on maize yield (p-values