Effect of Tied Ridges on Yield and Yield Components of Maize, Sorghum and Dry Bean Under Different Agronomic Management Practices in Central Kenya

Abstract

The principle factors causing low productivity of food crops under rain-fed agriculture are low soil fertility, unpredictable and poorly distributed rainfall that cause low soil moisture, poor crop management practices and soil runoff. Crop production, especially in Central Kenya, is mainly reliant on rainfall which has become less reliable owing to the changes in climate. Improving water efficiency is an important first step in buffering the effects of rainfall unpredictability. However, increasing availability of water alone cannot deliver the required benefits. It is therefore, important to incorporate measures to conserve soil water with the available agronomic practices such as application of inorganic fertilizer and use of proper plant density among others to improve yields of various field crops including maize, sorghum and dry beans. This study aimed to: (i) evaluate the effect of tied ridges under different levels of N and P fertilizer on the yield and yield components of maize and sorghum; and (ii) to determine the effect of tied ridges and planting densities on growth and yield of dry bean. The two experiments were conducted at Kabete Field Station Farm of the Faculty of Agriculture, University of Nairobi during the short and long rains of 2012 and 2013, respectively. In the first experiment, the tied ridges were incorporated with combined N and P fertilizers in randomized complete block design with a split plot arrangement. Tillage practices (conventional/normal tillage and tied ridges) were allocated to the main plots and fertilizer levels (zero fertilizer, 20 kg N ha-1 + 40 kg P ha-1 and 40 kg N ha-1 + 40 kg P ha-1) were allocated to the subplots for maize and sorghum which were planted separately and replicated three times. In the second experiment, tied ridges and varying plant densities of dry bean in a split plot design with tillage practices (conventional/normal tillage and tied ridges) assigned to the main plots and planting densities (20 cm x 45 cm, 15 cm x 45 cm and 12 cm x 45 cm) assigned to the subplots and replicated three times. Economic analysis was done using the prevailing market prices for input during the planting period and for outputs at the same time when the crops were harvested. All costs and profit were calculated on hectare basis in Kenya shillings. Tied ridges conserved moisture during the long rains of 2013 which resulted in significant improvement of maize grain yield, maize 1000-grain weight, sorghum stovers’ and sorghum panicle length. Maize yield and the weight of 1000 grains significantly increased when tied ridges were incorporated with 20 kg N ha-1 and 40 kg P ha-1 but further increase of nitrogen fertilizer to 40 kg ha-1 decreased the yield of maize but increased stovers’ yield. Also NP fertilizer application at the level of 20 kg N ha-1 and 40 kg P ha-1 significantly (p<0.05) xvi improved grain yield of maize, panicle length and number of grains per panicle of sorghum during long rains. However, incorporating tied ridges and NP fertilizer levels had no significant effect on maize and sorghum grain yield and other parameters observed during short rains. In the second experiment of dry beans, results obtained showed that, interaction between tied ridges and plant density had a significant (P<0.05) effect on the yield of dry bean but not on other related parameters during long rains of 2013. Beans planted under tied ridges at a spacing of 12 cm x 45 cm (185,185 plants/ha) had higher yields than bean planted at a wider spacing of 20 cm x 45 cm. Also, plant density had a significant effect on the number of pods per plant with density of 185,185 plants/ha recording the highest number. However, interaction between tied ridges and plant density had no significant effect on the yield of dry bean during the 2012 short rains. Generally, during the short rains season higher yield of dry bean was observed under conventional tillage than under tied ridges in all plant densities with beans planted at the density of 185,185 plants/ha recording higher yield than the density of 148,148 plants/ha. Under tied ridges, plant population of 148,148 plants/ha recorded the highest yield. There was a non-significant effect on other related parameters observed including pod length, number of seeds per pod, number of pods per plant and 1000-grain weight. In conclusion, it was found economical to incorporate tied with N and P combination at 20:40 kg ha-1 respectively for maize which gave the highest net profit in maize while for sorghum, conventional tillage with the same level of fertilizer registered the highest net profit. The study also showed that the highest profit was obtained in dry bean planted at a spacing of 12 cm x 45 cm (185,185 plants/ha) under tied ridges during the long rains. This was economically higher compared to the recommended spacing of 15 cm x 45 cm (148,148 plants/ha). Therefore, in Kabete region, tied ridges become effective when the rainfall is adequate but under drier conditions when the rainfall is low it is not necessary to integrate tied ridges with any combined N and P fertilizers or the plant densities studied