Potato and Tuber Crops

Irrigation

• In Kerala the crop is mostly grown under rain fed situation whereas in Tamil Nadu it is grown under irrigated condition. For proper establishment of cassava stakes/settlings (rooted cuttings) in the main field, sufficient moisture should be ensured in the field for the first twenty days after planting.
• A stress free condition always promotes higher tuber yield, as cassava has got a continuous growing period. Under irrigated condition, scheduling of the irrigation at 25 per cent available moisture depletion throughout the growing season could double the tube yield as compared to control .
• Supplementary irrigation at the rate of 20mm per week during the drought period significantly increased tuber yield of cassava over rain fed. Cassava requires sufficient soil moisture for sprouting of stakes and subsequent establishment. The bulk of the root volume is confined to the upper 20cm soil and the lateral spread of the root extended up to 45 cm under field conditions.
• The stage of the crop most sensitive to moisture is tuberization. Up to tuberizaion the crop needs irrigation at 10 days interval, and there after once in 20 days. Some of the studies conducted showed that 5 to 6 irrigation at 24 days interval during the drought period was optimum when water table is high.
• Under shallow water table crop requires irrigation 0.36 IW/CPE only, which approximately estimated to be of an interval of 37 days during the dry period. The response of cassava to irrigation water based on cumulative pan evaporation studies revealed that there is a linear response with level of irrigation from 0.3 to 0.9 IW/CPE.
• However, net profit increased marginally up to 0.6 IW/CPE only. Response of cassava to moisture stress at various stages of growth has been studied at sub-tropical climate and it has been observed that tuberization phase was most sensitive to moisture stress, which caused a yield loss of 32 per cent.
• Works carried out at CTCRI suggested that supplementary irrigation during dry period on the basis of IW/CPE ratio has increased the yield with low HCN content. IW/CPE ratio of 0.25 was on par with 0.5, 0.75 and 1.0 for low yielding varieties and for high yielding varieties IW/CPE ratio of 0.5 to 0.6 was optimum.
• Cassava is grown mainly as a rainfed crop in Kerala and irrigated crop in Tamil Nadu.
• Irrigating crop at 25% available moisture depletion level, could double tuber yield compared to irrigated crop.