Growth Parameters of DK8031 Maize Variety as Affected by Varying Irrigation and Nitrogen Fertilizer Rates in Embu County, Kenya

Determination of crop growth parameters of maize helps assess the performance of the crop for food security. A study was conducted in two seasons covering 2012 and 2013 to establish optimal irrigation and nitrogen fertilizer rates for drought tolerant hybrid maize （Zea mays L.）, DK8031 variety, in sandy loam soils using furrow irrigation. Four additive irrigation levels （119.05 mm, 238.10 mm, 357.15 mm and 476.2 mm） were allocated the main plots while five nitrogen fertilizer rates （0 kg/ha, 60, 75 kg/ha, 90 kg/ha and 100 kg/ha） were allocated the sub-plots. Both irrigation and nitrogen fertilizer treatments significantly enhanced crop growth parameters under consideration. Stand count per treatment plot, plant height and number of leaves per ranged from 45-59 plants/plot, 215-238 cm and 14-16 leaves respectively. It was concluded that use of supplementary irrigation and phased nitrogen fertilizer rates for maize growing in areas such as Embu can greatly promote crop growth.

基于干物质积累的滴灌玉米灌溉模型建立与校验

合理的灌水定额和阶段灌量分配是灌溉农业中灌溉制度的核心,它既是作物高产的前提,也是实现水资源高效利用的重要手段。本研究通过连续2年田间小区滴灌试验,研究了玉米阶段干物质积累量与灌水量和产量的关系,建立了基于阶段干物质积累的滴灌玉米优化灌量估算模型。结果表明:1)本研究基于滴灌玉米各生育期干物质积累量与阶段灌量、产量的关系,依次建立了滴灌玉米在拔节期、吐丝期、灌浆期和乳熟期的灌溉模型。2)由模型得到经济最佳灌量为6798m^3/hm^2;玉米在拔节期、吐丝期、灌浆期和乳熟期干物质积累量临界值分别为11241kg/hm^2、14104kg/hm^2、29194kg/hm^2和38842kg/hm^2,所需临界灌水量分别为1109m^3/hm^2、2252m^3/hm^2、4553m^3/hm^2和7741m^3/hm^2。3)经田间实际灌量检验,1:1直线间的决定系数(R^2)、根均方差(RMSE)和相对误差(RE)分别为0.8244、5.50%和0.12%,该模型可较好估算北疆地区滴灌玉米在经济最佳灌水量下进行优化阶段灌量分配。