Soil and water conservation techniques in cashew grown along steep hill slopes

Cashew (Anacardium occidentale L.), the highest foreign exchange earning perennial horticultural crop in India is generally grown as a rainfed crop along steep slopes of hills or on neglected land unsuitable for any other crop. In India, cashew experiences severe moisture stress from January to May, adversely affects its flowering and fruit set. In order to harvest the rainwater and to make it available to the cashew plant during critical period, an in situ soil and water conservation experiment was conducted at Directorate of Cashew Research, Puttur, Karnataka, India during 2003–2010. This experiment was laid along contour with five treatments namely, modified crescent bunds, coconut husk burial, reverse terraces, catch pits and control plot without any soil and water conservation. Among the treatments, modified crescent bund and coconut husk burial were superior. These two treatments reduced the annual runoff (22.3 and 20.4% of the annual rainfall compared to 36.9% of the annual rainfall in control), soil loss (47 and 49% of control) and nutrient loss. Also it increased the mean soil moisture content, growth of plants, yield of cashew (6.45 and 6.60 t/ha respectively compared to 4.88 t/ha in control for the first 5 harvests) and net profit from cashew garden (40% more than control). In addition to this, the groundwater level in nearby wells and ponds increased. Hence, the barren land even in steep slopes with proper soil and water conservation measures can be effectively utilized for cashew cultivation.

Research highlights▶ In India, cashew experiences severe moisture stress from January to May (critical period) which adversely affects its flowering and fruit set. In situ soil and water conservation measures such as modified crescent bund and coconut husk burial treatments were superior to other treatments in harvesting the pre-monsoon and post-monsoon rainfall and make it available to the cashew plant during this critical period. These treatments increased the growth of cashew plants and cumulative cashew yield (coconut husk burial—6.60 t/ha and modified crescent bund—6.45 t/ha) compared to control (4.88 t/ha) indicating 32–35% increase in yield. The net profit from cashew garden for the first seven years (5 harvests) with proper soil and water conservation ranged from US$ 4335 to 4332/ha whereas in control it was US$ 3097/ha. Modified crescent bund and coconut husk burial treatments reduced the annual runoff (20 and 22% of the annual rainfall compared to 37% of the annual rainfall in control) and soil loss (47 and 49% of control), increased the mean soil moisture content (15.6% and 15.8% dry basis compared to 11.6% dry basis in control in March), and nutrient content of the soil and leaf. The harvested rainwater increased the groundwater level in nearby wells and ponds. Hence, the barren land even in steep slopes can be effectively utilized for cashew cultivation with proper soil and water conservation measures like modified crescent bund or coconut husk burial in staggered trenches opened across the slope.