Length to weight ratio of chickpea roots under progressively receding soil moisture conditions in a Vertisol.
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Experiments were conducted in a Vertisol near Patancheru, Andhra Pradesh, under decreasing soil moisture conditions with five chickpea (Cicer arietinum) genotypes during the 1992-93 and 1993-94 post-rainy seasons. Roots were sampled at 14-day intervals using a monolith method. Changes in length-to-weight ratio (LWR) across genotypes, in general, were not significant as the genotypes had similar growth duration. With increasing age, root LWR declined gradually in the 0-10 cm depth and remained nearly unchanged in the 10-30 cm soil layer. It showed an apparent increasing trend at 30-135 cm soil depths, contrary to the observations made in other crops. Between the two seasons, root LWR was the lowest at all times and depths during the relatively wet 1992-93 season. The changes in LWR with increasing soil depth exhibited lowest values at the soil surface with steep increases in the middle layers and a constant or declining pattern in deeper layers. There was a clear negative relationship between available soil moisture and LWR in the lower half of the rooting zone at all stages of crop growth in both years, a possible effect of oxygen deficiency caused by excessive soil water status. Changes in root morphology over depth indicated that poor soil aeration decreased LWR in Vertisols
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