www.IndianJournals.com Members Copy, Not for Commercial Sale Downloaded From IP - 202.141.45.18 on dated 14-Mar-2011 Journal of the Indian Society of Soil Science, Vol. 56, No. 3, pp 267-275 (2008) Received July 2007; Accepted May 2008 Assessment of Critical Soil Water Potential for Emergence of Wheat, Chickpea and Linseed Seedlings in Relation to Water Stress in a Vertisol K.K. BANDYOPADHYAY* 1 , A.K. MISRA, P.K. GHOSH, K.M. HATI, M. MOHANTY AND R.K. SINGH Indian Institute of Soil Science, Nabibagh, Berasia Road, Bhopal, Madhya Pradesh, 462038 Abstract: Seedling emergence influences the initial plant population and hence the yield of any annual crop. Among the soil physical properties, soil water potential is the most critical factor influencing the seedling emergence. The narrow range of soil water for sowing operation and limited availability of irrigation water are the major constraints for seedling emergence and productivity of the dry season crops in Vertisols. A field experiment was carried out on a deep Vertisol at the Indian Institute of Soil Science, Bhopal to find out the critical soil water potential for the emergence of wheat, chickpea and linseed seedlings and to assess the amount of presowing irrigation required and the optimum time of sowing following the presowing irrigation for achieving the desired emergence of seedlings. Wheat, chickpea and linseed were sown after 1 to 9 days of drainage following application of six levels of presowing irrigation viz., 0, 2, 4, 6, 8, and 10 cm. The results showed that the critical matric potential for the initiation of emergence of wheat, chickpea and linseed was - 72.60, -68.65 and -72.76 kPa, respectively and the corresponding critical volumetric water content at the time of sowing was 0.17, 0.19 and 0.18 cm 3 cm -3 , respectively. It was estimated that for achieving 50% emergence, wheat, chickpea and linseed might be sown respectively at 4, 3 and 1 days after drainage of 8 or 10 cm presowing irrigation. The emergence rate index decreased significantly with the increase of matric suction of the seed zone caused by application of less amount of presowing irrigation or delay in sowing after application of a given amount of presowing irrigation. The logistic growth model successfully predicted the relative emergence of wheat, chickpea and linseed. Key words: Soil water potential, wheat, chickpea, linseed, Vertisol, emergence rate index, logistic growth model Seedling emergence, one of the important phenologi- cal event, influences the final yield of an annual crop. Soil physical factors that control seedling emergence and crop establishment are temperature, water con- tent, aeration and mechanical impedance of the seed zone (Schneider and Gupta 1985). Among these fac- tors, soil water potential is the most critical. These factors influence commencement, rate and percent- age of seedling emergence. Lack of adequate water results in decreased germination, final emergence and rate of emergence, as well as susceptibility of seeds to damage by pathogenic organisms (Hadas and Russo 1974). It also greatly affects seedling ability to withstand other stresses, including soil compaction and resistance (Stout et al . 1961). On the other hand, excessive water content can lead to an inadequate oxygen supply, which in turn can result in reduced seedling growth and higher potential for invasion by pathogenic fungi (Richard and Guerif 1988). The rate of water absorption by seeds, one of the prerequisite for seed germination and emergence, is dependent on the matric potential of the given soil, the seed-soil contact area and the hydraulic conductivity of the soil and seed (Hadas 1985). The timing of emergence often determines whether a plant competes success- fully with its neighbors, consumed by herbivores, infected with diseases, and whether it flowers, re- produces, and matures properly by the end of grow- ing season. Gan et al. (1992) reported that the wheat plants those emerged early contributed more towards crop yield than those emerged later. Thus desirable crop yields can be achieved by providing seeds with *Corresponding author (Email: kk.bandyopadhyay@gmail.com) Present address 1 Central Institute for Cotton Research, Regional Station, Marutha Malai Main Road, Coimbatore, Tamil Nadu, 641003