Mineral Fertilization of Potato Crop and Quantitative and Qualitative Characteristics in Southwestern Ethiopia

Abstract

A field experiment was conducted to determine the optimum rates of phosphorous (P) and potassium (K) fertilizers for high yield and better tuber quality of potato (var. Jalanne) on Nitisols of Jimma, in 2011/12 under rain fed conditions. Four levels of P (0, 20, 40 and 60 kg P ha-1) and three levels of potassium (0, 55 and 110 kg K ha-1) were combined in a 4x3 factorial arrangement in Randomized Complete Block Design (RCBD) with three replications. Data were collected on yield, and tuber quality parameters such as dry matter, specific gravity and starch content. The result of the study showed significant effects P and K fertilizers on major yield parameters: harvest index, total tuber yield, marketable tuber yield, total tuber number, marketable tuber number, tuber diameter, mean tuber weight and tuber quality parameters: dry matter content tuber specific gravity, and starch content. The higher total tuber number (11), marketable tuber yield (41.4 t ha-1) and total tuber yield (44.9 t ha-1) was obtained from the combined application of 60:110 kg of P:K ha-1. An increased P application levels resulted in a reduced dry matter content of potato tuber from 24.9 to 20.9%. The highest dry matter content was obtained with no P application while the lowest was obtained from application of 60 kg P ha-1. Unlike P, increased level of K nutrient application from 0 to 110 kg ha-1 increased the dry matter content from 21.1 to 24.4%. Similarly, increasing the application of P from 0 to 60 kg ha-1 significantly decreased specific gravity of the tuber while increasing K levels from 0 to 110 kg K ha-1 increased the tuber specific gravity. Further, higher levels of P and K increased the starch content of potato tuber. Starch content was relatively higher in tubers treated with K compared to P treatments suggesting that the use of higher rates of K in potato could tend to enhance starch content in potatoes.