Preliminary Evaluation of Different Combinations of Inorganic and Humate Based Fertilizer on Yield of Potato (Solanum tuberosum L.) in Malawi

In Malawi the demand of the use of mineral acidifying fertilizer by farmers for sustenance of high crop yields is increasing. The soaring demand is a pointer to the loss of humic substances in the soil and the resultant poor soil health. There is potential however to reduce the amount of mineral fertilizer used by the farmers and retain the applied nutrients within the plants rooting zone for increased use efficiency and productivity. This could be achieved through the combined application of humate based fertilizers with mineral fertilizer. Therefore, an experiment was conducted to evaluate the effect of different rates of NPK and humate based fertilizer (HBF) combinations on potato yield and yield components at Tsangano, Bembeke and Dwale Extension Planning Area (EPA) in the 2016/2017 cropping season. Ten treatments were laid out in a randomized complete block design (RCBD). Baseline soil data were collected and subjected to standard laboratory analytical procedure. Agronomic data collected in the experiment were analyzed in Genstat Discovery Edition 4 and were subjected to analysis of variance (ANOVA) at 95% level of confidence. The means were separated by the least significant difference (LSD0.05). Laboratory analysis showed that soils were strongly acid at the three sites with low amount of N, P, K except for Dwale EPA which had high P and medium content of K. Furthermore, results showed that different NPK and HBF combination significantly influenced potato tuber yield and yield components at the three sites. The recommended fertilizer rate of NPK 8:18:15 + 6S at 250 kg ha-1 + 60 kg N ha-1 produced the highest tuber yield at Tsangano (20,729 kg ha-1) and Bembeke (5,189 kg ha-1). At Dwale EPA, application of NPK 8:18:15 + 6S at 250 kg ha-1 produced the highest yield (13,956 kg ha-1). Nevertheless, different combinations of NPK and HBF fertilizer (Treatments 7, 8, 9 and 10) also gave comparably high yields and high number of big tubers. Therefore, the combined application of mineral fertilizer and humate based fertilizer potentially could increase potato yield in Malawi, sustainably. More studies however are required in order to confirm the results.