Weather Advisory for Cashew Growers
Contingency plan for rainfall deficit management for cashew
Most of the cashew plantations established in India are under rainfed conditions, and very few are under irrigation. The cashew adapted well in the west and east coast regions and subsequently spread to hilly and plain regions of Karnataka, Tamil Nadu, Gujarat, Chhattisgarh, and NEH States. The cashew is suitable for diverse climatic conditions and rainfall patterns ranging from scanty rainfall regions (around 800 mm) to heavy rainfall regions (around 4000 mm), thus showing its wide adaptability under varied moisture availability conditions. Moreover, cashew needs frost-free conditions.
If the monsoon is delayed by 15 – 30 days
The cashew is planted after the onset of the monsoon from June to September. If there is a delay in the onset of the monsoon, the plantation programme should also be delayed, coinciding with the monsoon. In fact, fresh grafts when planted require sufficient soil moisture for initial establishment, and hence, cashew is planted during the monsoon season. Whenever there is a drought situation after planting, they need protective irrigation. The irrigation through a pitcher (hold pots) is recommended in dry land situations.
Rain deficit at reproductive phase
Due to the non-uniform distribution of rainfall over the years, cashew experiences severe moisture stress, particularly during the reproductive phase from December to May, which adversely affects its flowering and fruit set, causing flower drying and immature nut drop. Under severe moisture stress situations, drying of flowers, poor fruit set and nut development owing to yield loss are observed. To overcome such problems, proper soil and water conservation measures like crescent bund, trenching, inward basin, etc, coupled with coconut husk burial or mulching, have been found useful. Supplemental irrigation of 200 litres of water/plant once in 15 days during January to March from water collected in ponds through rain harvesting helps in flowering and nut development by improving the microclimate with increased humidity. It also leads to increased nut and kernel weight by reducing flower and nut drying to some extent. Drip irrigation during fruit development stages, wherever water is available, may be helpful during drought situations for the rainfed cashew crop. Normally, for the west coast of Dakshina Kannada, irrigation by drip at 20 litres/tree/day for mature cashew plantations (10 to 15 years) is recommended.
Rain deficit at the vegetative phase
Established plants survive even in adverse soil moisture conditions. If the drought situation persists due to low rainfall in the rainy season, there is every possibility of the yield being affected. Under such a situation, to reduce the yield loss, one or two protective irrigations may be given wherever irrigation facilities exist. However, mulching of the basin by dry biomass helps conserve soil moisture.
Terminal drought
The rainfall deficit or cessation of rains at the early stage also adversely affects the cashew nut yield, particularly in late-maturing varieties. To maintain the proper soil moisture regime, the harvesting of rainwater and recycling it during the deficit period is suggested. Moreover, the adoption of soil conservation measures and the installation of drip wherever a water source is available will be helpful.
