Development of a CAZRI "Staggered Pitting Oisker" for water harvesting and increased pasture productivity in arid zones

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1 A/lIlC!S of Arid Zone--18 (l & 2), 96-1, 1979 Development of a CAZRI "Staggered Pitting Oisker" for water harvesting and increased pasture productivity in arid zones R.B. DAs and R.C. Y ADAV Central Arid Zone Research Institute, Jodhpur ( Received on ) INTRODUCTION Unstability in crop production due to low and erratic rainfall in arid and semi-arid areas necessitates the need for bringing appreciably large proportion of land use under grasses and pastures. Further, various suitable water conservation practices like contour bun ding, water harvesting and plugging of gullies etc. have been adopted to lessen the climatic hazard in the land under crops which otherwise are capable of giving good economic returns. Results of studies conducted by Wasiullah et al. (1972) have shewn that staggered furrowing is superior to contour bunding in different agroclimatic regions of western Rajasthan. Practice of pitting has been found effective in range and pasture lands (Anonymous, 1957). However, accomplishment of pitting on the hard ground of these rugged lands at faster speed has so far been a problem and its adoptability was limited because of non-availabilit y of suitable machinery and constructional aid. In United States and Australia a heavy equipment consisting of off-centre discs and other type jumping cultivator had been used for staggered pitting. These machines have so far been feasible under Indian conditions either because of high power requirement or because of high cost of fabrication. A staggered pitting disker simpler in constructional features over coming the limitations of high power and particularly suited to tbe mode of tractor power available in country, as developed at Central Arid Zone Research Institute, Jodhpur, has been described in this paper alongwith the reult obtained in field trial. FUllctional considerations: Grass and pasture land remains unploughed for many years, surface become harder to till unlike normal cultivated lands. Further, the grass roots offer great resistance to cutting and shearing. Therefore, a machine for operating in the grass and pasture should be able to give

2 A NEW STAGGERED PITTING DISKER : 97 effective depth of cut easily. The machine should excavate staggered pits for effective moisture conservation and watel' harvesting keeping area under pit in the range of 15-2 per cent with the least damage to the. grass tussocks. It should cover large area per unit time at comparatively lower costs of operation. As it has to work in the grass field where straw and residue remain in abundance, it should be of non clogging type. Description ; The disker consists of eleven 55 cm diameter standard disc segments (\2 sector at periphery retaining entire 1 cm diameter of disc in the centre) and could be drawn with tractor powers of the range of 3-35 H.P. These disc sectors are spaced at 23 cm apart with the help of standard spacers and bearings and supported by brace of size fixed in the square bar frame. The square bar frame is made of 1 x 4 x 6 mm section and 1.8 metre length and is fixed in a frame prepared with 6 x 3 cm channels with the help of boits and nuts. This frame pattern developed for the disker facilitates quick change of angle of gang i. e. disc angle for incrcased width of cut (Fig. I & 2). For the placement of soil at down stream side of pits only one gang has been provided on which all discs are mounted in one direction as in the case of harrow plough. A coulter disc of 55 cm size has been provided at the first end of gang which counter acts the torque occurring as a result of soil reaction on discs (Fig. 1 & 2). To a void clogging of gang and lowing the resistance. occurring on the disc frame as a result of impact of growing grasses, the disker frame has been kept at an height of 4S cm above the ground. Performance. The disker gives 2.4 m width of cut in one run which in turn at 3 km ph. working speed and 8% efficiency covers about.576 ha per hour. One revolution of gang covers an average forward distance of 1.25 metres resulting coverage of 3. sq metre area. The disker cuts 11 staggered pits of an average size of 45 cm x 1 cm x 1 cm covering the net area under pit coming to be 16.5 per cent of total land. Thus one operation of this disker creates about 4, staggered pits for water storage equivalent to 3 mm water/ha, besides enhancing the intake rate of the land. During the pitting soil is placed at down stream side which acts as barrier for water detentions. Further, minor cutting of grass clamps during operation helps fast regeneration of the grasses. Staggered pitting stimulates the operation of microplot water harvesting as runoff from micro catchment gets concentrated into the micropits. This

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4 .. R.B. DAS AND R.C. YADAV 98A Fig. 2. Staggered Pitting Disker

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6 A NEW STAGGERED PITTING DISKER : 99 sort of moisture conservation lcaos to high er moisture regimes in and around the pits where grasses grow profusely which otherwise remain under subnormal condition on the entire area. This partial area moisture contribution results in much higher yield than without pitting. It is expected that the disker may playa significant role in soil erosion control as pitting increases intake ra te and retains water, thereby lowering the runoff peak. Further, the pits work as stilling wells in trapping the eroded particles. However, under bare field conditions where grasses are not fully established occurrence of high intensity storms soon after the pitting may lead to higher soil loss from pitted field than no pitting. However, such chances are very rare. The mode of placement of soil in the down stream side of pits get reversed when tractor takes turn, the. soil turning action in the same direction could be achieved with the use of opposite pattern gangs having roll over mechanism for which remote control is required but unfortunatcly, :there exists no provision of remote control for the present in the tractor power available in the country. However, problem of soil placement in the reverse can easily be avoided by operating the disker on contour lines.' Table 1. Effects of pitting on average forage production (dry matter q/ha) on various pastures (Total of two cutting), 1976 Pasture Pitted Non-pitted Mean 1. Cenchrus ci/iaris F. Test N. S. Lasiurus sindicus 2. C. ciliaris SEm +.93 C. setigulls 3. C. ci/iaris + C. setigerus L. sindicus 4. Natural II 57 'F' test SEm ±.577 CO. at 5% 1. 59'7 CD. at 1% 2.99

7 1 R B. DAS AND R.C. YADAV The staggered pitting was performed with this disker in the four kinds of pastures, three sown and one natural pasture, the efficiency of moisture conservation and forage production have been evaluated and data are presented in Table 1. Forage production in the pitted areas was significantly higher than that in without pitting. Pitting resulted in the highest increase in the natural pasture (155%), followed by '99% in C. ci/iaris + C. setigerus + Lasillrus sindicus mixture and 47% in Cenchrus ci/iaris + Lasillrus sindicus over no pitting. Thus, besides soil and water conservation, use of the disker gives beneficial effect of increasing primary as well as secondary productivity in low rainfall area. It was further observed that in the pitted pasture particularly in sown one young grass seedling were coming up in the pits after the recession of monsoon season. This is as a result of collection of seeds and grass residues with the runoff water in the pits. The water and grass-residues provide more conducive envirnment for sprouting and emergence of grass seed.s thus help in self regeneration of grass lands. ACKNOWLEDGEMENT Authors are thankful to Dr. H. S. Mann, Director, Central Arid Zone Research Institute, Jodhpur, for his encouragement and facilities provided for development of the pitting disker. REFERENCES Anonymou Hand book on Range management near East-South Asia. Compiled by Food & Agri. Office. International cooperation administration, Washington pp Wasi Ullah, Chakravarty, A. K., Mathur, C. P. and Vangani, N. S Effect of contour furrows and contour bunds on water conservation in grasslands of Western Rajasthan. Ann. Arid Zone II (3 & 4 ) :