CHANGES IN SOIL CARBON AND NITROGEN DUE TO IRRIGATION DEVELOPMENT IN NEBRASKA SANDHILL SOILS

Carbon and N parameters were compared for nondeveloped and developed soils (predominantly mixed mesic, Typic Ustipsamments, and sandy, mixed mesic Entic Haplustolls). Soil samples were collected from four developed center pivot irrigation sites and from the nondeveloped corners at depth increments of 0- to 75-, 75- to 150-, and 150- to 300-mm. Total C, total Kjeldahl N (TKN), hydrolyzable were determined. In some cases, undeveloped soil contained more N and C than these steady-state values, suggesting that development tended to decrease the soil test values. If the undeveloped soil was lower in N or C than the steady-state value, development tended to increase the test value. Total C, TKN, hydrolyzable N, mineralizable N (both techniques), and inorganic soil N were all highly correlated. Refs.