Effect of leaf harvest on grain yield and nutrient content of diverse amaranth entries

Amaranth (Amaranthus spp.) is a popular crop grown throughout sub-Saharan Africa, where both the grain and leaves are consumed. Amaranth cultivars that offer multiple options to small-scale farmers to produce high foliage yields, high grain yields, or both high foliage and grain yields would be desirable. The objective of this study was to determine the effects of multiple leaf harvests on grain yield and grain nutrient content of diverse amaranth entries (breeding lines and cultivars). Trials were conducted at the World Vegetable Center in Arusha, Tanzania in 2013 and 2014. Seventeen amaranth entries were evaluated for grain yield without defoliation, or after four leaf harvests. Grain samples of 10 entries were evaluated for calcium, iron, zinc, protein, sugar, and fiber content. Highly significant entry and leaf harvest differences in grain yield, leaf yield, and calcium, zinc, and protein contents were detected both years. Differences among years were significant or highly significant only for leaf yield, number of leaves per plant and panicle length. The leaf yields of all the entries were lower in 2013 (year mean = 11 t/ha) than in 2014 (15.3 t/ha). Four leaf harvests reduced grain yield of all entries by at least 50% but did not affect grain nutrient content except for calcium. Under no-leaf harvest PARIS (A)-Sel and BRESIL (B)-Sel gave the highest grain yield in both years. PARIS (A)-Sel suffered the highest grain yield loss (87%) followed by BRESIL (B)-Sel (85%) in 2013, while BRESIL (B)-Sel showed the highest loss (90%) followed by PARIS (A)-Sel (84%) in 2014. ‘Madiira 2’ was the lowest grain yielder under both leaf harvest and no-leaf harvest in both years. ‘Madiira 1’ and ‘Madiira 2’, black seeded cultivars, gave high Fe and fiber contents except the rank of ‘Madiira 2’ was less consistent for iron cross the years. Three groups of entries could be distinguished: (1) entries that produced high grain yields only if plants were not defoliated; (2) entries that yielded ample leaves but relatively little grain; (3) entries that gave moderate amounts of grain and leaves. Our study suggests there is potential to develop amaranth cultivars for different purposes to meet the needs of amaranth producers.