Combined Application of Biofertilizers and Inorganic Nutrients Improves Sweet Potato Yields

Abstract

Sweet potato [Ipomoea batatas (L) Lam] yields currently stand at 4.5 t ha−1 on smallholder farms in Uganda, despite the attainable yield (45–48 t ha−1) of NASPOT 11 cultivar comparable to the potential yield (45 t ha−1) in sub-Saharan Africa (SSA). On-farm field experiments were conducted for two seasons in the Mt Elgon High Farmlands and Lake Victoria Crescent agro-ecological zones in Uganda to determine the potential of biofertilizers, specifically arbuscular mycorrhizal fungi (AMF), to increase sweet potato yields (NASPOT 11 cultivar). Two kinds of biofertilizers were compared to different rates of phosphorus (P) fertilizer when applied with or without nitrogen (N) and potassium (K). The sweet potato response to treatments was variable across sites (soil types) and seasons, and significant tuber yield increase (p < 0.05) was promoted by biofertilizer and NPK treatments during the short-rain season in the Ferralsol. Tuber yields ranged from 12.8 to 20.1 t ha−1 in the Rhodic Nitisol (sandy-clay) compared to 7.6 to 14.9 t ha−1 in the Ferralsol (sandy-loam) during the same season. Root colonization was greater in the short-rain season compared to the long-rain season. Biofertilizers combined with N and K realized higher biomass and tuber yield than biofertilizers alone during the short-rain season indicating the need for starter nutrients for hyphal growth and root colonization of AMF. In this study, N0.25PK (34.6 t ha−1) and N0.5PK (32.9 t ha−1) resulted in the highest yield during the long and the short-rain season, respectively, but there was still a yield gap of 11.9 and 13.6 t ha−1 for the cultivar. Therefore, a combination of 90 kg N ha−1 and 100 kg K ha−1 with either 15 or 30 kg P ha−1 can increase sweet potato yield from 4.5 to >30 t ha−1. The results also show that to realize significance of AMF in nutrient depleted soils, starter nutrients should be included.

Effects of Arbuscular Mycorrhizal Fungal Inoculation on Growth and Yield of Two Sweet Potato Varieties

“…The results are also in comparison with those of Mukhongo at al. [32] who observed that combined application of biofertilizers and inorganic nutrients improves sweet potato yield.…”

Application of Azotobacter, Vesicular Arbuscular Mycorrhiza and Phosphate Solubilizing Bacteria for potato cultivation in Central Plain Zone (Pb-3) of Punjab

“…All the treatments where biofertilizers were supplied showed significantly better yield in comparison to plants fertilized with 100% of NPK from inorganic sources (T ) which could be 1 attributed with efficient utilization of nutrients to promote high photosynthetic rate, formation of medium size tubers and increase in production of dry matter in tuber as reported by Dash and Jena (2015); Nandekar et al (2006); Zargar et al (2008) and Farag Jr. et al (2013) during their investigations. Mukhongo et al (2017) reported highest yield in sweet potato due to application of biofertilizers in combination with inorganic fertilizers.…”

Involvement of nitrogen in storage root growth and related gene expression in sweet potato (Ipomoea batatas)

“…Sweet potato ( Ipomoea batatas ) is one of the most important food crops worldwide (Bovell‐Benjamin ; Shekhar et al ., ; Mukhongo et al ., ). China is a major producer of sweet potato, the production of sweet potato was 72,031,782 tonnes in China, producing approximately 64% of the world's supply (FAOSTAT, ).…”

“…China is a major producer of sweet potato, the production of sweet potato was 72,031,782 tonnes in China, producing approximately 64% of the world's supply (FAOSTAT, ). Optimized field N management is an important issue in sweet potato cultivation because N is a major factor for growth and productivity (Mukhongo et al ., ; Duan et al ., ). Nitrogen affects vegetative growth, storage root growth and development, as well as dry matter accumulation in sweet potato (Mukhongo et al ., ; Duan et al ., ).…”

“…Optimized field N management is an important issue in sweet potato cultivation because N is a major factor for growth and productivity (Mukhongo et al ., ; Duan et al ., ). Nitrogen affects vegetative growth, storage root growth and development, as well as dry matter accumulation in sweet potato (Mukhongo et al ., ; Duan et al ., ). It has been reported that a low N concentration might increase sweet potato storage root number at an early growth stage (Wilson, ).…”