Amelioration of a degraded ultisol with hardwood biochar: Effects on soil physico-chemical properties and yield of cucumber (Cucumis sativus L)

Abstract

A study was conducted in two consecutive cropping seasons to assess the effect of biochar on soil properties and yield of cucumber (Cucumis sativus L) in an intensive cucumber–maize rotation based system of Abakaliki, Southeastern Nigeria. Five rates of hardwood biochar (0, 2.5, 3.75, 5 and 6.25 t ha-1) were used for the study. The study was laid out as a randomized complete block design (RCBD) with five treatments and four replications. Data were collected from both soil and plant parameters. Soil samples (0 to 20 cm) were collected before and at harvest from different plots for soil chemical analyses. Results obtained from the study showed significant (P<0.05) improvement in soil properties. Bulk density (BD) was significantly (p<0.05) decreased in biochar amended plots. Total nitrogen (N), available phosphorus (P), organic carbon (C), pH and exchangeable bases (K+, Ca2+, Mg2+ and Na+) were significantly (p<0.05) higher in biochar amended plots relative to the control. Biochar application significantly (p<0.05) increased vine length, number of fruits, fruit length and yield of cucumber compared to the control. On average, 6.25 t ha-1 rate of biochar application gave the highest improvement in soil properties while highest increase in yield and other agronomic parameters were observed in 5 t ha-1 rate of application. The study recommended 5 t ha-1 as the maximum rate of biochar application in the study area. Our results indicated that biochar application could be a possible way of improving soil properties and native soil carbon in the degraded ultisols and intensive cropping systems. Key words: Mineral fertilizer, organic inputs, small holder farms, soil productivity, sustainable agriculture.