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Field Validation of Soil Solute Profiles in Irrigated Cotton
Author(s) -
Norton E. Randall,
Silvertooth Jeffrey C.
Publication year - 1998
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1998.00021962009000050010x
Subject(s) - loam , irrigation , fertilizer , environmental science , agronomy , leaching (pedology) , randomized block design , hydrology (agriculture) , mathematics , soil water , soil science , biology , geology , geotechnical engineering
Management of water and fertilizer N are important aspects of cotton production in the desert Southwest. GOSSYM, a cotton growth simulation model, has been used extensively to manage these inputs. Our objectives were to further validate GOSSYM by comparing model‐simulated and measured soil NO ‐ 3 ‐N profiles, to evaluate GOSSYM's potential as a management tool under irrigated growing conditions in the desert part of the U.S. Cotton Belt, and to address questions about the way GOSSYM simulates NO ‐ 3 ‐N movement through the soil profile in relation to irrigation water management (which in turn affects prediction of plant growth and development). We compared measured profiles of NO ‐ 3 ‐N with GOSSYM‐simulated profiles. Soil profile samples were obtained from an existing N‐management field study, a split‐plot within a randomized complete block design. Mainplots were upland and pima cotton ( G. hirsutum L. cv. DPL 5415 and G. barbadense L. cv. Pima S‐7, respectively). Subplots were a check (0 fertilizer N) and three other N‐management strategies. The cotton was grown on a Casa Grande sandy loam [fine‐loamy, mixed, hyperthermic Typic Natrargid (reclaimed)] near Maricopa, AZ, in 1994 and 1995. Fertilizer N rates ranged from 0 to 350 kg ha −1 in 1994 and 0 to 392 kg ha −1 in 1995. Soil samples taken to a depth of 120 cm in 30‐cm increments were analyzed for NO ‐ 3 ‐N. Comparisons of simulated and actual NO ‐ 3 ‐N profiles revealed tendencies in GOSSYM to overestimate NO ‐ 3 ‐N leaching out of the effective rooting zone, resulting in simulated N stresses midseason. When GOSSYM simulated an N stress, between 50 and 75% of the simulated soil NO ‐ 3 ‐N values were greater than the measured values, yet the simulated N stress still occurred. This indicates possible limitations in GOSSYM's ability to adequately predict N uptake by plants. The dynamic soil N portion of the model needs further refinement, particularly for cotton production under irrigated desert conditions.