Effects of wood biochar and potassium fertilizer on soil properties, growth and yield of sweet potato (Ipomea batata)

Studies on integrating biochar with potassium (K) fertilizer is not common. Hence, experiments were conducted in 2020 and 2021 to evaluate the sole and combined applications of biochar and K fertilizer on soil properties and performance of sweet potato. It was hypothesized that the effects of combined applications of biochar and K fertilizer on the growth, and yield of sweet potato will be more than their individual applications. The study each year consisted of a 3 x 3 factorial experiment with three levels (0, 10, and 20 t ha-1) of wood biochar and three levels (0, 70, and 120 kg ha-1) of K fertilizer (potassium chloride). The 9 treatment combinations have three replications and follow a randomized complete block design. Results revealed that biochar alone or in combination with K fertilizer improved soil physical and chemical properties, growth, and yield of sweet potato relative to the control and K fertilizer alone. The interaction of biochar and K (biochar x K fertilizer) fertilizer was significant for growth and yield parameters. The addition of K fertilizer to biochar improved the performance of sweet potato compared with sole applications of K fertilizer or biochar. 20 t ha-1 biochar +70 kg ha-1 K fertilizer and 20 t ha-1 biochar +120 kg ha-1 K fertilizer increased growth and yield relative to 10 t ha-1 biochar +70 kg ha-1 K fertilizer and 10 t ha-1 biochar +120 ha-1 kg K fertilizer. Since 20 t ha-1 biochar +120 kg ha-1 K fertilizer and 20 t ha-1 biochar +70 kg ha-1 K fertilizer were statistically similar, for this experiment, 20 t ha-1 biochar +70 kg ha-1 K fertilizer would be recommended for sweet potato production. Therefore, the addition of 70 kg K fertilizer with biochar has reduced the cost of increasing the rate to 120 kg ha-1 which would have been economical in view of the high price and lack of K fertilizer in Nigeria and other sub-Saharan African countries.

Automated summary

The study found that the combined application of biochar and potassium (K) fertilizer has positive effects on soil properties, growth, and yield of sweet potato. Adding an appropriate amount of K fertilizer to biochar is more beneficial for the growth and yield of sweet potato compared to applying K fertilizer or biochar alone.