EFFECT OF SALINE WATER ON SOIL CHEMICAL PROPERTIES AND AMARANTHUS GROWTH IN THE COASTAL KENYA

Abstract

Water is an essential resource for life and its availability and quality are central for a healthy ecosystem. The beginning of 21st century is marked by global fresh water shortage attributed to robust population growth, climate change effects among other factors. Aaccessibility of quality water has been a major challenge to land productivity within Kenyan coast, leading to reliance on underground water. Owing to vicinity to the ocean and underground minerology, the water is affected by sea water intrusion in many areas making it either very saline or brackish, hence unfavorable for productive agriculture. A study was carried out in September 2019-January 2020 to assess the suitability of saline water for irrigation and its effects on soil chemical properties and amaranthus (Amaranthus dubius Mart. ex Thell.) growth in Coastal Kenya. The study was done by use of structured survey and field experimentation. Survey was carried out by purposely selecting a total of sixty farmers owning boreholes and practicing irrigated agriculture within Kilifi and Kwale Counties. Data on farmers perception on water salinity and its effects on soil fertility and crop growth was evaluated using structured questionnaire. Data collected include: socio-demographic profiles, farmers’ source of agricultural management information, history of borehole, crop grown and soil and water management, soil and water samples for chemical analysis. Questionnaire data was subjected to descriptive statistics using SPSS. Evaluation of effect of saline on amaranthus growth was carried out by establishment of greenhouse experiments for 60 days at Pwani University in Kilifi County and in Mivumoni in Kwale County. The experiment was laid in randomized complete block design with three replications. The treatments were; fresh water (control), 75% saline water, 100% saline, fresh water + 0.45 g of diammonium phosphate (DAP), saline + DAP, 75% saline + DAP. Data collected in field experiment included: emergence rate, plant vi height, leaf number, leaf area, chlorophyll content, leaf temperature, root density, root weight, root volume and total plant biomass. Obtained data was subjected to analysis of variance using SAS software and means separated using Tukey’s test at p≤0.05. Survey results showed that majority of the farmers (67-87%) had limited information on the effects and management of saline irrigation borehole water and soils. Borehole irrigation water had high salinity (EC>3 dS/m and high chloride (Cl>30 meq/L). All (100%) of interviewed farmers in both Counties reported that their borehole water had not been tested for quality. Borehole irrigation water increased soil EC in the study sites by 45%. Fresh water plus DAP improved amaranthus growth in both Pwani University (56%) and Mivumoni (54%) compared to 100% saline water plus DAP. It can be concluded that despite the fact that borehole water within the research area have high levels of salinity, and farmers have limited knowledge on water salinity and its effects on soil fertility and crop growth. There is therefore need for capacity bulding farmers on the various water salinity levels, their effects and possible management approaches for improved crop production and food security.