UTILIZATION OF COW DUNG BIOSLURRY FROM ANAEROBIC DIGESTION AS FERTILIZER IN IMPROVING SOIL FERTILITY AND MAIZE PRODUCTIVITY IN KIAMBU COUNTY, KENYA

Abstract

Increasing demand for food triggered by increasing population prompts a reciprocal increase in food production. Bioslurry has potential to improve crop productivity. However, bioslurry quality varies, influenced by biodigester type. Similarly, quantities required in maize production is not well understood. This research sought to assess effects of i. biodigester type on nutritional content of bioslurry, ii. bioslurry from different biodigester types and when integrated with inorganic fertilizer on soil chemical properties, maize growth and yield, grain quality and profitability. Field experiments were established in Waruhiu Farmers’ Training Centre, Githunguri, in randomized complete block design (RCBD), split plot arrangement. The biodigester types, Flexi and Dome, were main plots while the subplots were 100%bioslurry(BS), 75%BS+25%fertilizer, 50%BS+50%fertilizer, 100%fertilizer and control. Soils were tested before and after two consecutive seasons for pH(water), exchangeable acidity, total nitrogen (N), total organic carbon (ToC), exchangeable phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), copper (Cu), iron (Fe), zinc (Zn) and manganese (Mn). Grains were analyzed for grain N, P, K, Ca, Mg, Zn, Cu, Mn and Fe. Growth and yield parameters were analyzed using SAS Version 10. Bioslurry from Flexi contained higher contents than Dome in most analyzed nutrients by more than 50%. Dome bioslurry treated soils increased soil pH, TN, OC, Ca and Mn by 4, 36.7, 37.2, 1.4 and 89.6% respectively. The other nutrients increased more in Flexi treated soils. Biodigester type did not cause any significant difference (P≤0.05) in growth and yield. In Integrations, highest increase in pH, TN, TOC and exchangeable Mn was noted in 100%bioslurry of 5.9%, 38.9%, 35.5% and 112.5% respectively, and decreased exchangeable acidity (EA) most by 4.5%. Soil pH decreased only in 100%fertilizer by 4.8%. Exchangeable P and K increased most in 100%fertilizer by 46.4% and 73.6% respectively. Mean plant height in short rains was highest in 75%BS+25%fertilizer, by 40.6%, while 100%fertilizer increased most by 20.7% in long rains. Stovers and stalk yields were highest in 100%bioslurry in short rains by 45.5% and 42.2%. In long rains, 100%fertilizer increased stovers and stalk yields most by 49.6% and vi 51.9%. Grain yields were not statistically(P≤0.05) different in all treatements in both seasons except in control. Gross income was higher in 100%fertilizer (29.2%) during short rains. In the same period, gross income was higher in 100%bioslurry from Dome of 19.3% compared to Flexi. However, net income was highest in 100%bioslurry from Dome, by 39.4% and 31.5% above control and Flexi respectively. During long rains, 75%BS+25%fertilizer gave higher gross income of 85.3%. The 100%bioslurry from Dome registered 23.1% higher gross income than Flexi. Similarly, net income was highest in 100%bioslurry from Dome, by 172.1% and 61.2% above control and Flexi respectively. Bioslurry from either biodigester types and its integration with inorganic fertilizer contributed to improved chemical properties of soil, maize growth, yields and grain quality comparable to 100%fertilizer and hence can be promoted for adoption. A longer term experiment is recommended for concretisation of these findings. Key words: Maize, Bioslurry, Cow dung, Organic Soil Amendment, Fixed dome and Flexi (Tubular) biodigesters