Impact of soil fertility management practices on the nutritional quality of Soybean (Glycine max (l.) Merr.) varieties grown in Eastern Zambia

Zambia has three primary agro-ecological regions, with each region having specific ecological characteristics. Region II agro-ecological zone of Zambia has low nutrient reserves and poor water holding capacity due to moderately leached clayey to loamy soil; this has led to low soybean productivity. Soil fertility management (ISFM) strategies such as the use of inorganic fertilizers and the use of inoculants of rhizobia have been introduced and promoted among small-scale farmers in Eastern Province. Two soybean varieties (Lukanga and Kafue) were used for this study and 96 samples from on-farm soil fertility management trials in Chipata, and Petauke districts were collected for the determinations of nutritional and anti-nutritional properties. The proximate analysis of Chipata samples showed that the ash content 5.10-6.23%, fat content 17.71-25.57%, protein content 27.73-37.11%, amylose content 1.26-4.56 %, sugar content 6.75-9.62%, and starch content 4.00-18.57%, while anti-nutritional properties ranged between 3.07 and 8.21% for phytate and 1.42-3.35% for tannin. With Petauke, the ash content 3.32-6.8 %, fat content 19.16-26.85%, protein content 27.68-35.62%, amylose 2.00-4.37%, sugar content 6.23-9.76%, and starch content 5.70-18.63%. Phytate and tannin contents were 3.37-7.90% and 0.14-3.32%, respectively. The highest protein content was found at the level of 37.11% in Kafue with 40kg P/ha and inoculant, and the least was 27.73% for Lukanga without inputs in Chipata while in Petauke, Lukanga with 40 P/ha and inoculant had the highest protein content of 35.62% and the least was 27.68% for Lukanga with inoculant. The co-application of rhizobia inoculant and P nutrient increased phytate, and tannin content significantly (P < 0.05).