Rooting depth and soil water extraction patterns of different crops in a silty loam Haplustoll

This study was carried out: (i) to estimate from soil water depletion curves the apparent rooting depth (RD) for several crops; (ii) to calculate the soil water extraction parameters; and (iii) to compare inter- and intraspecific differences in the water extraction parameters. Experiments were conducted at the Manfredi Experimental Station (WTA), Argentina (31 degrees 49' S, 63 degrees 48'W), and at the Institute of Phytopathology and Vegetal Physiology (IFFIVE), Cordoba, Argentina (31 degrees 24' S, 64 degrees 11' W). The soil was a silty loam Entic Haplustoll (USDA Soil Taxonomy) with A, AC and C horizons. The crops studied were: maize (Zea mays L.), sunflower (Helianthus annuus L.), peanut (Arachis hypogaea L.), soybean (Glycine max L. Merr.), and alfalfa (Medicago sativa L.). Differences in apparent rooting depths among species and cultivars, ranging from 130 to 290 cm, were found. The comparison of the extraction front velocity (EFV) revealed differences among species but not among cultivars of the same species. EFV ranged from 44 mm day(-1) for sunflower to 23 mm day(-1) for peanut. In all the crops, the downward progress of the extraction front stopped at the beginning of the grain filling. Comparisons among the pooled rates of water extraction (kl) for depths from 10 to 110 cm, revealed significant differences among crops and cultivars within crops. The kl values ranged from 0.110 day(-1) for Contiflor 3 sunflower to 0.029 day(-1) for alfalfa. No significant correlation between kl values and root length density over 40 to 120 cm depths was found for soybean, indicating that the specific water uptake rate varies considerably in the soil profile. (C) 1997 Elsevier Science B.V.