S.Manivannan and A.K.Sikka JAE : 50 (3) Journal of Agricultural Engineering Vol. 50 (3): July-September, 2013 Hydrological Impact of Bioengineering Conservation Measures on Cashew Plantations in Lateritic of Konkan Region S.Manivannan1 and A.K.Sikka2

Manuscript received: February, 2013 Revised manuscript accepted: July, 2013

Abstract

Hydrological impact of various bioengineering conservation measures viz. Half-moon Terraces + Vetiveria zizanioides + Stylosanthes scabra, continuous contour trench + Vetiveria zizanioides + Stylosanthes scabra, graded trench + Vetiveria zizanioides + Stylosanthes scabra, staggered contour trench + Vetiveria zizanioides + Stylosanthes scabra and semi-elliptical trench + Vetiveria zizanioides + Stylosanthes scabra on three-year old cashew plantations were assessed on lateritic of Konkan region in Goa State. The study revealed that the bioengineering measures tried in cashew plantation on hill slope had a significant effect in reducing annual runoff, soil loss and nutrients losses. Bioengineering measures reduced runoff by 5 to 12.8% as compared to no-conservation measure. Out of all the bioengineering measures, continuous contour trenches with Stylosanthes scabra and Vetiveria zizanioides, followed by staggered contour trenches with Stylosanthes scabra and Vetiveria zizanioides reduced runoff by 12.8 and 10.3%, respectively. Continuous contour trenches with Stylosanthes scabram Vetiveria zizanioides and staggered contour trenches with Stylosanthes scabra and Vetiveria zizanioides reduced soil loss by 11 and 8 t.ha–1.yr-1 in cashew field, respectively. Minimum major nutrients losses were monitored in the treatment of continuous contour trenches with Stylosanthes scabra and Vetiveria zizanioides, followed by staggered contour trenches with Stylosanthes scabra and Vetiveria zizanioides, while the maximum nutrient losses was recorded in control plot. The highest soil and efficiency was observed in continuous contour trenches withStylosanthes scabra and Vetiveria zizanioides (47.4%), followed by staggered contour trenches with Stylosanthes scabra and Vetiveria zizanioides (35.9%) and it was lowest (18.3%) in half-moon terraces with Stylosanthes scabra and Vetiveria zizanioides. It was concluded that the continuous contour trenches with Stylosanthes scabra and Vetiveria zizanioides as vegetative barrier was most efficient as compared to all other treatments for runoff, soil loss and nutrient loss reduction. Staggered contour trenches with Stylosanthes scabra and Vetiveria zizanioides was the alternative measure for reducing runoff and soil and nutrient losses in cashew land use.

Key words: Bioengineering measures, cashew, continuous contour trenches, lateritic soils, nutrient loss, runoff, soil loss, staggered contour trenches

Majority of the soil series in Konkan region are coarse to imbalances (Manivannan, 2004). Most of the hilly areas medium textured and well drained with poor water holding in Goa are under perennial horticultural crops. Among the capacity. Crops like cashew, mango, arecanut, coconut etc. entire horticultural crops, cashew is the most predominated are predominantly occupying the steep slopes of lower crop, which occupies an area of 54,858 ha. The present level coastal ghats and central undulating uplands of Konkan of productivity is only about 466 kg.ha-1, which is less as region. In steeply sloping regions of western ghats, the compared to the national average of 660 kg.ha-1. The major cultivation of orchard crops without adopting proper soil factors for low productivity are loss of fertile soil due to and water conservation measures has resulted in siltation and inadequate moisture in root zones of crops of channels and small reservoirs. With erosion, due to excess runoff. Quantification of runoff and soil large quantity of the fertile soil is transported from the loss is prerequisite for recommending any soil and water fields. The slope gradients range from 5 to 25% (70.8% of conservation measures for adoption in farmers’ field. total area) and in some places up to 40% (20.6% of total area), and thus it has become necessary to adopt soil and Many authors quantified the runoff and soil loss in both water conservation measures for raising agricultural crops conventional practices and conservation practices. Dilshad in the region to avoid soil degradation and ecological et al. (1996) found that conventionally tilled catchments

1 Senior Scientist (S&WCE) (Email: [email protected]), Central Soil & Water Conservation Research & Training Institute, Research Centre, Fern Hill (Post), Udhagamandalam-643 004, Tamil Nadu; 2 Technical Expert & Member, National Rainfed Area Authority, Planning Commission, Government of India, New Delhi

57 July-September, 2013 Hydrological Impact of Bioengineering Conservation Measures

produced 1.5-2 times more runoff and lost 1.5-6 times MATERIALS AND METHODS more soil than their no-tillage counterparts. Conservation measures such as hillside ditches, intermittent terraces, Study Area contour bunds and bench terraces reduced soil loss from The study was conducted at Research Farm of ICAR 31 t.ha-1.yr-1 in the cash crop planting plot to 12, 10.8 and Research Complex for Goa of North Goa district of Goa 5 t.ha-1.yr-1, respectively. The average annual runoff from State, India. The experimental site lies in between 15° 29’ these conservation measured plots was about 90, 87, 82 28” North latitude and 73° 55’ 14” East longitudes, and and 79 mm, respectively, which was a little less than (91 located 69 m above mean sea level. The mean slope of mm) that of the bare area (Tangtham and Korporn, 1997). the experimental site is 19 per cent. The study area has a Forest canopy cover in combination with higher warm tropical climate with an average annual temperature capacities of the forest land reduced the erosive runoff of 26.4º C.The soil temperature regime is isohyperthermic. from the forest watershed, and thus the soil loss (Cox et The southwest monsoon yields a total annual precipitation al., 2006). Several workers have reported runoff, soil and of about 2800 mm from June to October from an average nutrient losses under different agro-ecological situations of 122 rainfall events. Mean annual total evaporation in India (Rai and Singh, 1986; Kale et al.,1988). Kale et is 1473 mm. Soil series is a member of gravelly clay al. (1988) reported that the untreated watershed recorded isohyperthermic family of Oxic Dystropepts. The soils have 20 times more runoff over the treated one in north Konkan dark medium acid clay loam and gravelly clay B horizon region. The runoff and soil losses increased with increase with 20 to 30% quartz gravels and semi-hard laterite C in land slope and varied with agronomic cover crops in horizon. They are developed on laterite and occur on hill north Konkan region. Vinod et al. (2003) stated that the slopes with 10 to 15% slope gradient in parts of Panaji. development of natural vegetation in the land use system The thickness of solum is 30 to 45 cm and mean annual reduced the runoff from 23 mm to 12 mm and soil loss from soil temperature is 27.1 ºC. The thickness of A horizon is 5 79.8 kg.ha-1 to 22.5 kg.ha-1in cardamom land use system to 15 cm. Its colour is in 5 YR hue 3 to 5 value and 4 to 6 chroma. The texture is gravelly sandy loam, gravelly clay in Western ghats of Karnataka. Badhe and Magar (2004) loam to gravelly clay loam with 15 to 30% quartz gravels. reported that trapezoidal shaped staggered trenches were The thickness of B horizon is 25 to 30 cm and has colour in most effective for reducing , soil and nutrient 5 YR hue 3 to 5 value and 4 to 6 chroma. The texture ranges losses under hilly terrain in lateritic soils of Konkan region from gravelly clay loam to gravelly sandy clay loam and of Maharashtra. Khola and Sastry (2005) found that there clay loam to gravelly clay with 20 to 30% quartz gravels. was a significant reduction in runoff by 92.2, 79.1, 63.8 and Soil is well drained with moderate permeability and medium 23.9% and soil loss by 95.8, 88.8, 80.1 and 37.0% under deep with medium available moisture retaining capacity. bench , contour bund, graded bund and contour Soil type is classified as land capability subclass – III to farming, respectively, compared to cultivated fallow under IV. The soil of the experimental site was acidic with pH of maize-wheat cropping sequence in foothills of Western 5.4 to 5.6 and EC of 0.10 to 0.14 dS.m-1 and CEC ranging Himalaya. Manivannan (2010) stated that the continuous from 11.8 to 12.7 C mole (p+).kg-1. Better organic carbon contour trenches with Stylosanthes scabra and Vetiveria content (0.79 to 1.11%) was observed in the experimental zizanioides was found to be the best conservation measure site. The available nitrogen and phosphorus content of the to retain soil moisture for longer duration after cessation soil was low (44 to 107 and < 15 kg.ha-1, respectively) while of monsoon. In-situ bioengineering measures (continuous available potassium was medium (128 to 226 kg.ha-1). contour trenches with Stylosanthes scabra and Vetiveria zizanioides) made significant impact on nut and apple Details of Experiment quality of cashew in terms of increase in nut weight, apple The study was conducted in three-year old cashew weight, TSS and juice content as compared to the cashew plantations in each plot size of 75 x 17.5 m in the cashew grown without bioengineering measures (Manivannan et al., field where the cashew variety Goa-1 was planted in 4 m 2010 a). However, the information on runoff and soil loss x 4 m spacing. In these plots, five types of bioengineering under bioengineering measures in hilly terrain of lateritic measures were imposed in five plots, and the remaining soils under cashew land use is very limited. Hence, the one plot was kept as control plot without any conservation present investigation was conducted to quantify the impact measure to compare the treatment effects. The details of soil of different bioengineering measures on runoff as also soil and water conservation treatments imposed are presented in and nutrient losses under cashew land use in lateritic soils Table 1. A line drawing of treatments imposed is depicted in of Konkan region. Fig.1. Time replication was followed for three-year period

58 S.Manivannan and A.K.Sikka JAE : 50 (3)

Table 1. Details of conservation measures imposed for cashew plantation

Treatment Specifications

T1- Half-moon terraces with Semi-circular terraces were made down stream side of the plant at a distance of 1.5 m Stylosanthes scabra and Vetiveria radius. Inward slope was maintained and two rows of Stylosanthes scabra followed by one zizanioides (HMT + VB) row of Vetiveria zizanioides at a spacing of 50 cm were planted at the edge of the terrace.

T2 – Continuous contour Trenches for field length with top width of 0.45 m, bottom width of 0.30 m and depth of trenches with Stylosanthes 0.45 m were made continuously along the contour at vertical interval of 1 m. Two rows of scabraandVetiveria zizanioides Stylosanthes scabra followed by one row of Vetiveria zizanioides at a spacing of 50 cm (CCT + VB) were planted as vegetative barriers on the down stream side of the trench bund.

T3 – Graded trench with Trenches for field length with top of 0.45 m, bottom width of 0.30 m and depth of 0.45 m Stylosanthes scabra and Vetiveria were made with 1 per cent grade. Two rows of Stylosanthes scabra followed by one row zizanioides of Vetiveria zizanioides at a spacing of 50 cm were planted as vegetative barriers on the (GT + VB) down stream side of the trench bund.

T4- Staggered contour trenches Trenches of length of 2m, top width of 0