Seasonal Variation on Soil Nutrient Availability for Plant Use and Farmers Adaptation Strategies in North Bank Region of The Gambia

Abstract

This study examined seasonal variation on soil nutrient availability for plant use and farmers adaptation strategies in North Bank Region of The Gambia. The aim was to evaluate nutrient levels in the soil interface by determining changes in soil nutrient availability for plant use during wet and dry season. Soil samples were collected in three upland fields at a depth of 0-15cm and analysis were done on this variables: pH, Soil organic carbon (SOC), total nitrogen (TN) and soil moisture content. Soil pH was measured using the glass electrode method with a soil-to-water ratio of 1:2. Soil total nitrogen was determined using the micro Kjeldahl distillation and titration method. Soil organic carbon (SOC) was determined by a modified Walkley-Black procedure. The gravimetric method of moisture estimation was used to dry the soil samples on the oven at 105 °C and dried to a constant weight. Plant tissue (groundnut) was collected within 1m2 wooden frames and prepared for routine analysis of total nitrogen (TN), total carbon (TC) and moisture content. Socio-economic data was obtained from 105 respondents through household interview. Rainfall data was obtained from Water Resources of The Gambia to determine the trends in the study area. The result show that soil moisture content, soil total nitrogen and soil pH were found to be significant (P<0.05) in different seasons indicating variation in nutrient content in the productive soil depth due to the influence of moisture deficiency except soil organic carbon which shows no significant difference. In addition, variation of available plant nutrients content within the communities showed that higher plant total nitrogen was received during wet season in Nuimi Lamin 3.18 % followed by Jokadu Dasilami with 2.84 % while Njaba Kunda is having the least 2.20 %. During dry season there was no significant (P<0.05) different of plant total nitrogen among communities. Meanwhile Plant total carbon also showed a significant (P>0.05) difference within the communities during wet season, Nuimi Lamin having the highest percentages (53.11% followed by Jokadu Dasilami with 51.12% while Njaba Kunda recorded the least 36.88 %). During dry season there was no significant (P<0.05) difference in plant total carbon. It is establish that majority of the farmers are between 40-60 years of farming experience and have limited knowledge of farm management practices. Farmers use both chemical and organic fertilizers mostly to manage their soils as adaptation strategies. Rainfall trend in the study area was found to be 35 % lower (425 mm) than normal 1200 mm. The study also concluded that soil degradation and drought in the region is a challenge, therefore it is recommended that farmers should be encouraged to practice organic farming and avoid harvesting the entire crop biomass which can conserve moisture and increase soil fertility.