Inorganic fertilizers are widely used for crop production, but their long-term impacts on soil organic carbon (SOC) pools and soil physical attributes are not fully understood. We studied how half a century of N application at 0, 45, 90, 134, 179, and 224 kg ha -1 and P application at 0, 20, and 40 kg ha -1 (since 1992) affected SOC pools and soil structural and hydraulic parameters in irrigated continuous corn ( Zea mays L.) under conventional till on an Aridic Haplustoll in the central Great Plains. Application of 45, 90, 134, 179, and 224 kg N ha -1 increased the SOC pool by 4.6, 6.8, 7.6, 7.9, and 9.7 Mg ha -1, respectively, relative to nonfertilized plots in the 0- to 45-cm depth. Application of 20 kg P ha -1 increased the SOC pool by 2.9 Mg ha -1 in the 0- to 30-cm depth. The highest N rate increased the SOC pool by 195 kg ha -1 yr -1. The C gains may be, however, offset by the C hidden costs of N fertilization. Application of >45 kg N ha -1 reduced the proportion of soil macroaggregates (>0.25 mm) in the 7.5- to 30-cm depth. Fertilization did not affect hydraulic properties, but application of ?90 kg N ha -1 slightly increased aggregate water repellency. An increase in SOC concentration did not increase the mean weight diameter of wet aggregates ( r=0.1; P>0.10), but it slightly increased aggregate water repellency ( r=0.5; P<0.005). Overall, long-term inorganic fertilization to irrigated corn can increase SOC pool, but it may reduce soil structural stability.
