title: Soil nitrate nitrogen dynamics after biosolids application in a tobosagrass desert grassland.
abstract: Dormant-season application of biosolids increases desert grass production more than growing season application in the first growing season after application. Differential patterns of NO3-N (plant available N) release following seasonal biosolids application may explain this response. Experiments were conducted to determine soil nitrate nitrogen dynamics following application of biosolids during two seasons in a tobosagrass [Hilaria mutica (Buckl.) Benth.] Chihuahuan Desert grassland. Biosolids were applied either in the dormant (early April) or growing (early July) season at 0, 18, or 34 dry Mg ha(-1). A polyester-nylon mulch was also applied to serve as a control that approximated the same physical effects on the soil surface as the biosolids but without any chemical effects. Supplemental irrigation was applied to half of the plots. Soil NO3-N was measured at two depths (0-5 and 5-15 cm) underneath biosolids (or mulch) and in interspace positions relative to surface location of biosolids (or mulch). Dormant-season biosolids application significantly increased soil NO3-N during the first growing season, and also increased soil NO3-N throughout the first growing season compared to growing-season biosolids application in a year of higher-than-average spring precipitation. In a year of lower-than-average spring precipitation, season of application did not affect soil NO3-N. Soil NO3-N was higher at both biosolids rates for both seasons of application than in the control treatment. Biosolids increased soil NO3-N compared to the inert mulch. Irrigation did not significantly affect soil NO3-N. Soil NO3-N was not significantly different underneath biosolids and in interspace positions. Surface soil NO3-N was higher during the first year of biosolids application, and subsurface soil NO3-N increased during the second year. Results showed that biosolids rate and season of application affected soil NO3-N measured during the growing season. Under dry spring-normal summer precipitation conditions, season of application did not affect soil NO3-N; in contrast, dormant season application increased soil NO3-N more than growing season application under wet spring-dry summer conditions.
authors.affiliation: Campo Experimental "La Campana", Instituto Nacional de Investigaciones Forestales Agrícolas y Pecuarias (INIFAP), Chihuahua, Chih., México 31100.
authors.forename: Pedro
authors.initials: P
authors.lastname: Jurado-Guerra
authors.forename: David B
authors.initials: DB
authors.lastname: Wester
authors.forename: Ernest B
authors.initials: EB
authors.lastname: Fish
mesh_terms: D003889:Desert Climate; D005308:Fertilizers / Q000032:analysis; D008670:Metals / Q000032:analysis; D009566:Nitrates / Q000032:analysis*; D009584:Nitrogen / Q000032:analysis; D006109:Poaceae / Q000254:growth & development*; D012722:Sewage / Q000032:analysis; D012987:Soil / Q000032:analysis*; D013781:Texas
chemical_list: D005308:Fertilizers; D008670:Metals; D009566:Nitrates; D012722:Sewage; D012987:Soil; D009584:Nitrogen