| Abstrakt: |
"Phosphorus and water deficits are important limiting factors in agricultural production. A field experiment was carried out with soybean(Glycine max (L.) Merr.) to determine whether the effect of water stress on field-grown soybean changes with soil P availability, and whether soil water content affects plant P nutrition. The soil was a Sadler series (fine-silty, mixed, mesic Glossic Fragiudalf) located at Princeton, Kentucky, USA (37 deg. 60? north, 87 deg. 60? west). The experiment was a factorial with three levels of soil P availability (4,19 and 32 mg kg-1, Mehlich III) and two of water (irrigated and non-irrigated). Most of the effects of phosphorus and water stress on soybean growth were additive, so that, in general, effects ofwater stress were similar at each P level. Phosphorus deficiency slowed vegetative development, reduced shoot growth, LAI, P absorption and concentration, seed number, size and yield, and increased root length density in the surface soil. Water stress accelerated crop maturity, reduced shoot growth, LAI, P absorption and concentration, seed number, size and yield, and increased root length density. Some interactions between P and water were observed. Water stress slowed vegetative development only at the lowest P level (P0). The crop had a positive response to increasing P availability in both situations, with and without irrigation, suggesting that P addition would be justified even when a dry growing season is likely to occur. [ABSTRACT FROM AUTHOR] |
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