Abstract
The effect of nitrogen and potassium on the yield and water use efficiency of sweetpotato (Ipomoea batatas L.) was studied under water stress condition. The treatments consisted of two soil water regimes (30% and 80% of the soil field capacity) and nitrogen and potassium treatments (20, 100, and 200 kg of N ha-1, with a non-limiting potassium supply (160 kg of K ha-1) and 16, 80, and 160 kg of K ha-1, with a non-limiting nitrogen supply (200 kg of N ha-1). The experiment was carried out in complete randomized design with 4 replications. The supply of nitrogen and potassium at 100 kg N ha-1 and 160 kg K ha-1 produced the highest tuber yields under both well watered and water stressed conditions. A higher nitrogen supply in the soil produced greater leaf area, but increasing soil nitrogen beyond 100 kg N ha-1 reduced tuber yields. Leaf area and yields of Lole cultivar were less affected by water stress than were those of Wanmun cultivar. Under water stress conditions, Wanmun cultivar produced lower tuber yields than did Lole cultivar. Plant water use efficiency increased as the potassium supply increased under adequate and water-stressed conditions in both Lole and Wanmun cultivars.
Highlights
Sweetpotato is the fifth most important food crop in developing countries after rice, wheat, maize and cassava (FAO, 2002)
The treatments consisted of two soil water regimes (30% and 80% of the soil field capacity) and nitrogen and potassium treatments (20, 100, and 200 kg of N ha-1, with a non-limiting potassium supply (160 kg of K ha-1) and 16, 80, and 160 kg of K ha-1, with a non-limiting nitrogen supply (200 kg of N ha-1)
The greater leaf areas produced by lower potassium supply were attributed to the presence of non-limiting nitrogen contents in the soil
Summary
Sweetpotato is the fifth most important food crop in developing countries after rice, wheat, maize and cassava (FAO, 2002). Sweetpotato is source of human food, animal feed and processed products. It is the most important staple food crop which constitutes 80% of rural people’s diet in Papua, Eastern Indonesia. Intensive research efforts to enhance production and consumption have been undertaken in recent decades with the aim of increasing recognition of the potential of sweetpotato as a nutritious food for humans and animals (Yamakawa & Yoshimoto, 2002). Tuber yield of sweetpotato in Papua, Indonesia is low, with an average yield of 10 ton ha-1 (Saraswati et al, 2013). Soil moisture is considered amongst the most important factors affecting yield, as it affects root development and could impose a significant impact on yields (Yamauchi et al, 1996)
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