Physiological, biochemical and yield responses of maize and banana plants under Calliandra calothyrsus, Sesbania sesban and Leucaena diversifolia intercropping in Vihiga county, Kenya

Abstract

Increasing population leads to demand for more food. Consequently, there is need to expand agricultural land, necessitating cutting down of trees. This however, leads to soil degradation. Nutrient depleted soils and poor cropping systems such as continuous cropping, have contributed to the declining yield, which is a major problem facing farmers in Western Kenya. Intercropping with agroforestry tree species can alleviate soil infertility problems and increase crop productivity through enhanced biological nitrogen fixation, growth and photosynthesis hence ensuring food security. However, intercropping with agroforestry trees may lead to competition for both above ground and below ground resources between crops and trees hence affecting growth, physiology, biochemistry and yield of the component crops. Intercropping maize and bananas with agroforestry trees such as Calliandracalothyrsus, Sesbaniasesban and Leucaenadiversifolia have the potential to improve the growth and productivity of both maize and bananas and as a result alleviate food insecurity. However, the influence of the agroforestry trees species on the growth, gas exchange, nutrient uptake and yield of the crops is yet to be established. This study sought to investigate the influence of intercropping agroforestry tree species on maize and banana height, number of green leaves, leaf area, stem diameter, transpiration rate, intercellular CO2 concentration, net photosynthesis, total chlorophyll content, uptake of N, P, K, Mg, Ca nutrients and yield. The field trials were set up at Maseno University farm in Vihiga County. Seeds of agroforestry trees were acquired from KEFRI – Muguga, planted in a seedbed and the seedlings raised in nurseries. Five months old Williams’ variety tissue banana seedlings were obtained from KALRO-Thika. Hybrid maize seeds, H513 were bought from Kenya seed company Kitale. Banana holes were dug 90cm x 90cm x 60cm deep and 20 Kg of cow dung manure + 20 Kg of top soil + 200g of NPK fertilizer added before planting the banana at a depth of 0.3m for proper anchorage. Maize were planted at 0.75 m inter row by 0.3 m spacing. Randomized Complete Block Design with 3 replications and seven treatment levels (maize without fertilizer, maize banana Calliandracalothyrsus, maize banana Leucaenadiversifolia, maize banana Sesbaniasesban, maize-banana, banana monocrop and maize with fertilizer) were used. Fifteen maize and four banana plants in each treatment were sampled in a zigzag method and tagged for data collection. Data on plant height, stem diameter, number of leaves, leaf area, and yield (grain weight, banana bunch weight, banana number of fingers and finger length) were determined. Gas exchange and chlorophyll content index parameters were measured using infrared gas analyser and SPAD meter, respectively on the 3rd fully sun exposed leaf of the tagged plants. Kjeldahl method was used to determine plant tissue N content. Ca, Mg and P contents were determined using atomic absorption spectrophotometer, while atomic emission spectrophotometer was used to determine K contents. Data collected from the study was subjected to analysis of variance using GenStat statistical package. Treatment means were also separated and compared using the least significant difference. Correlation analysis was carried out on plant height, leaf area, net photosynthetic rate, intercellular CO2 concentration and transpiration rate to determine the relationship between the parameters. There were significant increases (P ≤ 0.05) in plant height of maize, stem diameter, number of leaves, net photosynthesis, intercellular CO2 concentration, transpiration rate, chlorophyll content, nutrient uptake and yield under maize + banana + sesbaniasesban (MBS) intercropping. There were no significant differences (P ≥ 0.05) in plant height of banana plants under the agroforestry tree species intercropping. Bunch weight and finger length were significantly higher under MBS. There was significant strong positive correlations (P ≤ 0.05) between net photosynthesis and leaf area, net photosynthesis and transpiration rate, net photosynthesis and intercellular CO2 concentration, leaf area and intercellular CO2 concentration in both maize and banana plants. These agroforestry trees enhanced growth, physiological, biochemical and yield of maize and bananas. Therefore, intercropping of maize, banana and Sesbaniasesban is recommended as it increased the yields of both maize and banana through improved growth, photosynthetic rate and mineral nutrient uptake. This study allows us understand the interaction mechanisms of the crops of maize and banana crops with the three agroforestry tree species to resources.