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G. RAJITHA*, A. MUNEENDRA BABU, G. PRABHAKARA REDDY AND P. SUDHAKAR
Department of Agronomy, S.V. Agricultural College, ANGRAU, Tirupati-517 502, Chittoor Dt., A.P.
A field experiment was conducted during kharif, 2016-17 at S.V. Agricultural college farm, Tirupati to study the effects of in-situ moisture conservation techniques on the productivity of rainfed groundnut (Arachis hypogaea). Broad bed and furrow system were effective in conserving the soil moisture leading to improvement in yield attributes and pod and haulm yields of
groundnut. The highest pod yield of 2056 kg ha-1 was recorded with broad bed and furrow system.
Broad bed and furrow system, groundnut, morphological attributes, rainfed, yield.
Soil moisture is the limiting factor for groundnut
( Arachis hypogaea) productivity under rainfed conditions. Much work has been done and is being directed towards more sustainable measures for conserving soil moisture. Promising and potentially appropriate methods such as contour and graded bunds, fallowing and mulching have been developed. Nevertheless, the rate of farmer adoption of these practices remains notably low and is still insufficient for conservation of moisture. This suggests the need for much more simpler methods of moisture conservation with minimum external input and investment. Prolonged drought periods are common, especially during moisture sensitive stages of flowering, pegging and pod development, leading to lower yields. Keeping in view, the importance of groundnut crop, which is predominantly grown during kharif season in Chittoor district of Andhra Pradesh, the present experiment was carried on yield attributes and yield of rainfed groundnut (Arachis hypogaea) as influenced by different moisture conservation measures.
The field experiment was conducted on sandy loam soil (Alfisols) during rainy season at Tirupati. The experimental soil was neutral in reaction (7.5 pH), medium in organic carbon (0.58 %) and low in available nitrogen (176 kg ha-1 ), medium in available phosphorous (70 kg ha-1) and high in available potassium (304 kg ha-1). Moisture content at field capacity and permanent wilting point was 14 and 4 per cent respectively, with bulk density
of 1.5 g cc-1. There were eight soil moisture conservation methods. All these were tested in randomized block design, and replicated thrice. The treatments were conventional tillage (T1), vertical tillage with subsoiler upto a depth of 60 cm at an interval of 1.0 m followed by secondary tillage (T2), deep ploughing with mouldboard plough upto a depth of 40 cm followed by secondary tillage (T3), conservation furrow after every row (T4), conservation furrow after every four rows (T5), broad bed and furrow (T6), straw mulch @ 5 tonnes ha-1 (T7) and soil mulch (frequent intercultivation) (T8).
Rainfall during the crop period was about 340 mm which was received in 20 rainy days. The crop was subjected to about 30 days moisture stress from August first week to September second week compared to relatively uniform distribution except for about 20 days from August first to third week. In general, rainfall was ideal for growth and development of groundnut. Heavy rainfall from September first week to October which was coincided with reproductive stage of crop had favorable effect on groundnut yield.
Soil moisture at 0 – 30 and 30 – 60 cm soil depth during period of crop growth was measured gravimetrically to assess the influence of these treatments on the productivity of groundnut.
Soil moisture content during crop period of groundnut was relatively high (10.9%) with vertical tillage
with subsoiler which was comparable with deep ploughing (10.1%) and least in conventional tillage (8.3%). With regard to moisture conservation practices, broad bed and furrow method of moisture conservation maintained consistently higher soil moisture at every soil sampling and superior over rest of the treatments.
Conservation furrows may be effective on vertisols with low infiltration rate and high moisture retentive capacity. When rainfall exceeds infiltration rate of the soil, excess water will be collected in furrows thereby giving more opportune time for the soil to soak the water. When once the water infiltrated into vertisol, it will be retained in the soil for long, as it has higher moisture retentive capacity. Therefore, this method was effective on vertisols. Unless the intensity of rainfall is too high, alfisol can take almost all the rainfall because of its high infiltration rate. The shallow depth and hence its low saturation need does not permit storage of water in the soil. Once the soil is saturated there will not be any beneficial effect of water collected in the furrows as it leaves the soil as runoff. Hence, conservation furrow method was not effective on alfisols.
Soil mulch was also not effective in conserving soil moisture. This was due to the fact that there was no difference in moisture conservation treatment between conventional tillage and soil mulch except that soil mulch was done during 20 days interval. Hence there was no appreciable difference in soil moisture content due to these two treatments. In view of the above drawbacks with conservation furrows, soil mulch and conventional tillage methods, subsoiling, deep tillage methods and broad bed furrow method of moisture conservation resulted in high soil moisture content all through the crop period.
Among moisture conservation practices, broad bed and furrows resulted in higher number of pegs (54), total
(48) and filled pods (25.1). Relatively low moisture content with conservation furrows, straw mulch and soil mulch practices resulted in lower number of pegs, total and filled pods plant-1.
The superiority of subsoiling, deep ploughing and broad bed and furrows over other treatments could be explained on the basis of increased moisture and nutrient availability in altered moisture conservation techniques. This could also be supported by better physical condition of soil, i.e., lower bulk density, enhanced permeability, better aeration and lower penetration resistance making
the soil to remain soft and moist due to the in-situ water harvesting by reducing runoff losses. Venkateshwarlu and Malaviya (2004) also reported similar findings. The 100 pod weight, 100 kernel weight and shelling percentage also followed similar trend because of adequate available soil moisture with subsoiling, deep tillage practices and broad bed and furrow method of moisture conservation. Similar increase in yield attributes with broad bed and furrows were reported by Nimje (1992).
Pod and haulm yields were higher due to subsoiling which were on par with the yield in deep tillage. There was significant reduction in conventional tillage as compared to above two methods. Among moisture conservation practices, highest pod yield of 2056 kg ha-1 was obtained from broad bed and furrow method of planting followed by straw mulch, while soil mulch recorded the lowest pod yield. The reduction in pod yields in soil mulch as compared to BBF method was due to lesser number of pegs, lesser total and filled pods or plant-1. The poor physical condition of the soil mulch method probably made it difficult for peg penetration and pod development.
Haulm yield also followed similar trend as that of pod yield. Higher haulm yield was with those treatments where the soil moisture was high due to broad bed and furrows. Increase in haulm yield with adequate soil moisture was observed by Venkateshwarlu (2006).
From the results, it is evident that subsoiling, deep tillage methods and broad bed and furrow system of moisture conservation practice are effective for conserving rain water leading to higher productivity of rainfed groundnut on sandy-loam soil.