Variations in soil pH, N, P and K due to influence of rates, split applications of nitrogen fertilizer and ratoon crop of sugarcane varieties

Abstract

Fertilizer Best Management Practices (BMPs) include soil testing that is performed to determine the availability of essential elements for profitable and productive yields of crops. The objective of this research was to establish the influence of nitrogen fertilizer either applied in single or split to ratoon crops of new (D8484) and old (CO421) varieties on soil nutrient levels. The experimental design was a 2x4x3 split split-plot on a continuation of research at the Sugar Research Institute, Opapo, where the plant crop received similar treatments. Analysis of soil nutrient levels was done using recommended methods. The results revealed that despite the randomization of the treatments, the pH was lower (p≤0.05) in D8484 plots than the CO421 plots. However, both at the start and harvest of ratoon, the pH remained within the range suitable for sugarcane growing. A general decline in soil pH with high rates of nitrogen was observed. Precisely, there was a higher pH decline at 15-30 cm soil depth compared to 0-15 cm soil depth. On the other hand, splitting nitrogenous fertilizer application did not affect the soil pH. The varieties did not influence soil nitrogen levels at the beginning of the ratoon and harvest. Although soil nitrogen level was low where nitrogen had not been applied, this was only significant (p≤0.05) for variety CO421 at the start of ratoon. Splitting nitrogen application recorded a significantly (p≤0.05) lower effect on soil nitrogen levels for variety D8484 than CO421 at the start of ratoon at 15-30 cm soil depth. There were no significant effects of the treatments on soil P levels. Soil K considerably (p≤0.05) dropped due to variety D8484 at 0-15 cm at harvest and both start of ratoon and harvest at 15- 30 cm soil depth. It is concluded that variety D8484 acidifies the soil more than CO421. However, the pH endured the levels appropriate for sugarcane growth both at the start of the ratoon and harvest. Current agronomic practices did not lead to much change in soil N and P. The study recommends that soil sampling and testing should not be frequently done since the treatment effects on soil physico-chemical parameters could manifest after a long period.