Abstract

Abiotic shades due to the high level of cloud are the major problem causing a low level of sweetpotato (Ipomoea batatas L.) photosynthesis in the higland of Papua, Indonesia. In order to optimize the growth and production of sweetpotato, it needs to engineer the growing environment for the crop. This study aims to learn the growth, production and photosynthesis efficiency (Eµ) by combining varieties and sticks inclination angles on (1.560 m asl) from April to September 2016. It was conducted using a Split-Plot Design with three replications. The main plot was three sweet potato varietes: Siate, Papua Salosa and Cangkuang, while the subplot was the inclination of sticks with three angles: 90º, 60º, 45º and without using sticks. The result shows that a combination of Cangkuang and 90º stick inclination produces the highest total dry matter and tubers (326.9 g/plant and 248.7 g/plant respectively). The highest net assimilation rate was obtained in combination of Cangkuang with stick inclination angles treatments 90º and 60º for 125.2 mg.cm2.day-1 and 105.3 mg.cm2.day-1, the leaf area index ranged from 0.9-5.5. The highest tubers yield was achieved by the Cangkuang with 90º and 60º sticks inclination angles treatments, which are 31.53 t.ha-1 and 28.86 t.ha-1 respectively, with the harvest indexes around 36-62 %, in which the tubers yield and the harvest indexes have significant correlations. The highest photosynthesis efficiency was achieved by the Cangkuang with 90º (3.83 %) and 600 (3.34 %) sticks inclination angles treatments, while the lowest one was done by the Siate and without sticks (0.92 %) treatment. As a conclusion, the higher sticks inclination angles applied on the sweetpotato varieties, particularly whose wider leafs, under abiotic shade conditions may increase crop growth rates, total and tuber dry matters, tubers yield, harvest indexes, and photosynthesis efficiency rates.

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