The growth and development of taro, Colocasia esculenta (L) Schott, in relation to selected cultural management practices

Abstract

Field and greenhouse studies were conducted to determine the effects of management practices on taro. Three irrigation methods, three land preparation methods and three population combinations were studied. Factorial combinations of water treatments, age, and nutrients were used to study individual plant response in pots. A cost analysis based on yield from the irrigation experiment and data from puddled flooded soil condition (population, 27 X 103 plants per hectare) was presented. Corm yields were 25, 35 and 26 metric tons/ha at 7, 10 and 13 months under sprinkler irrigation; 27, 41 and 62 tons/ha under furrow and 33, 48 and 64 tons/ha for flooded soil at the same ages respectively. Flooding gave significantly higher total yields over sprinkler at all ages whereas significantly higher yield over furrow was obtained only at 10 months. The yield from furrow irrigation was 82% of yield from flooded plot and that from sprinkler was 75% at 7 months. Corresponding percent yields at 10 and 13 months from the sprinkler and furrow irrigated plots were 75 and 85; and 41 and 97. Corm yield per hectare increased with increasing population. Yield per plant increased as population decreased. The contribution of sucker corms to total yield per plant increased as plant population decreased, while sucker yield per hectare increased as population increased. Suckering was not enough to compensate for increases in yields due to increasing population per hectare. Both greenhouse and field experiments showed that sucker yield was highest in flooded soil and decreased with decreasing water level. Effect of ridging ranged from 94% to 101% of yields obtained from non-ridged plots. Puddling of soil was not essential in taro growth. Yield from unpuddled flooded soil ranged from 92 to 106% of yield from puddled, flooded soil. Corresponding yields from unpuddled furrow and sprinkler irrigated plots were 88 and 92%; and 65 and 58%, respectively. Leaf area of taro can be accurately evaluated by linear dimensions. Both plant height and leaf growth approached a maximum between 4 and 5 months irrespective of irrigation and land preparation methods. Leaf area increased as follows: flood> furrow> sprinkler. The best linear relationship of leaf area with yield was obtained at 3 months (r = 0.83**) and not at 5 and 10 months (r = 0.56**). Leaf production at 5 months in excess of amounts required for optimum corm yield was demonstrated. Maximum leaf area indices (LAI) obtained at 5 months were 6.9, 6.2 and 4.7 respectively for flooded, furrow and sprinkler irrigation. Regression of corm yield and LAI showed that LAI approached 3.0 for optimum corm yield. A distinct optimum was established at this value in the sprinkler treatment while a plasticity in LAI and yield was observed in the furrow and was extreme in the flooded culture. Compared with returns from puddled flooded culture, relative incomes at 27 X 103 plants per hectare were as follows: Sprinkler 52 - 68%, furrow 72 - 87%, flooded unpuddled 70 - 96%. Owing to higher rate of senescence of leaf growth, the N, P, Ca, Mg, Fe and Mn concentrations of taro petiole at 6 months were higher under the sprinkler and furrow irrigation than in flooded samples. There were no differences at 3 months. The N, K, Fe and Mn concentrations at 3 and 6 months were significantly higher under ridged culture in contrast with non-ridged culture. Based on 2-month vegetative growth in a pot study, increases in yield due to application of N and P at 800 and 1200 kg/ha under non-flooded culture was not enough to offset the difference in growth due to flooding. Restricted root growth and penetration were among factors limiting taro growth under non-flooded culture in the pot study. The data presented showed that the difficulty of heavy machinery use in taro culture could be minimized with no significant difference in yield by improved crop management practices. Cultural adjustments suggested include saturated soil by furrow irrigation of non-puddled soil with 60 cm ridge or row spacing and 30 cm (or less) plant spacing. Where machinery specifications make it impracticable for 60 cm ridge or row spacing to be used, a 90 cm spacing could be substituted with no loss in yield. Pot study showed that N and P rates in excess of 800 and 1200 kg/ha, respectively, might be required.