EFFECTS OF PLANT DENSITY AND NITROGEN APPLICATION ON LEAF AREA INDEX (LAI) AND MAIZE YIELD IN A RECLAIMED WETLAND OF NYERI COUNTY, KENYA.
Maize is the main staple food in Kenya. Over 90% of Kenyans rely on maize with an annual per capita consumption of 94 kg. The annual maize production in Kenya is about 2.7 million metric tonnes and is slightly lower than the domestic consumption above which translates to roughly 37.8 million bags (3.4 million metric tons) per year. Kenya‘s average production per hectare is about one twentieth of that attained in other countries such as Argentina. Maize yield is more affected by variations in plant density than other members of the grass family. The study was carried out to determine the effects of plant density, fertilizer application as well as the wetland conditions on the maize yield. This study investigated the effect of N application at 120 kg N/ha and plant density on the Leaf Area Index and maize yield grown on reclaimed wetland soils in Karatina, Nyeri county during the short rain season of 2012 and long rain season of 2013. Treatments were laid in a randomized complete block design with three replications. Leaf Area Index (LAI) was determined directly using copy method and indirectly using Sun scan. Measurements were carried out every 10 days till physiological maturity. Initial soil sampling was carried out in September 2012 at the start of the trial and subsequent soil sampling at the end of each season (after maize harvesting) and selected analyses done. Maize yield was also determined after harvesting and sub sampling done per plot excluding the guard rows. The treatments applied were as follows: 100 *12.5 (-N), 100 * 12.5 (+N), 100 * 25 (-N), 100 * 25 (+N), 50 * 12.5 (-N), 50 * 12.5 (+N), 50 * 25 (-N), 50 * 25 (+N). Results indicated that nitrogen application affected total N, C and pH of the reclaimed wetland soil. The leaf area index increased with Nitrogen application and reduced with increase in spacing for most treatments, however grain yield did not change significantly with the application of Nitrogen fertilizer. All treatments correlated positively with the grain yield depending on spacing and availability of N at (p ≤ 0.05). In relation to grain yield, it is shown that the treatment 50 cm *12.5 cm (-N) had the highest yield (p ≤ 0.05) of 4.2 t/ha followed by 50 cm * 12.5 cm (+N) (3.6 t/ha). Lowest yields (p ≤ 0.05) were however recorded in the 100 cm * 25 cm (+N) treatments with 1.7 t/ha. There were no significant differences between the two LAI methods (Copy Method and SunScan). It was concluded that high plant density gives high LAI, which contributes greater grain yield. Application of Nitrogen also increased the grain yield as well as the Leaf area Index. Plant spacing of 50 cm * 12.5 cm (-N) and 50 cm * 12.5 cm (+N) are recommended.
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