Soil water and nutrient change in stands of three perennial crops

Perennial grains have potential as alternative crops for low-input agricultural systems. This study was conducted to describe seasonal and spatial patterns of soil water and nutrient change in experimental stands of wildrye [Leymus racemosus (Lam.) Tsvelev], eastern gamagrass [Tripsacum dactyloides (L.) L.], and Illinois bundleflower [Desmanthus illinoensis (Michx.) MacM.]. Changes in soil water pressure, organic C, and nutrient concentrations were monitored regularly at three depths 5-15, 35-45, and 90-100 cm) from March 1988 through October 1989, and soil nutrients were sampled again in April 1991 and March 1992, to document species differences in resource use and effects on soil nutrient balance with time. During the first two growing seasons, crops showed strong seasonal and spatial differences in resource extraction. Annual precipitation in 1988 and 1989 was below normal. Soil water pressure under bundleflower stands declined rap. idly by mid-summer 1988 and approached -1.5 MPa at 100 cm by late summer 1988. Water pressure declined more gradually in the grass stands, remaining generally highest in wildrye. Bundleflower and gamagrass depleted relatively more sod water in summer, whereas wildrye used relatively more soil water in spring and autumn 1989. Inorganic N increased at 10 and 40 cm in wildrye stands in the first year and remained higher than in stands of the other two species from late 1988 through late summer 1989. In general, P increased at 10 cm in grass stands, especially in wildrye. Otherwise, there were few consistent differences among species in levels of soil C, P, K, Ca, Mg, and pH during the first two growing seasons. After three years, soil organic C was generally highest in gamagrass stands, whereas NO3- concentration was highest for wildrye. The next year, however, NO3- was highest in wildrye at 100 cm only.