No abstract

Water redistribution in a complex landscape needs to be quantified in order to determine field productivity. Landscape effects on water use and spring wheat (Triticum aestivum L.) yields were studied by monitoring two fields at each of two locations in North Dakota for 5 years. Four soil series at different positions within each field were monitored: the Zahl loam series (fine‐loamy, mixed Entic Haploboroll) on hilltops and shoulder positions, the Williams loam series (fine‐loamy, mixed Typic Argiboroll) on side slopes and hilltops, the Bowbells loam series (fine‐loamy, mixed Pachic Haploboroll) on footslopes and toeslopes, and the Tonka silt loam series (fine, montmorillonitic, frigid Argiaquic Argialboll) in small undrained depressional areas. Topographic factors were calculated at each site by measuring the slope in four directions, 90° apart, and adding the slopes together. If a slope was downward toward a site, it was considered positive, if a slope was upward toward a site it was considered negative. This number, if positive, would indicate that runon water would be added to the site and, if negative, water would be lost from the site due to runoff. Topographic factors were calculated 3, 6, 15, and 30 m from each site. As expected, wheat yields from the four soils were in the order Tonka > Bowbells > Williams > Zahl. Spring wheat grain yields ranged from 5.1 Mg ha−1 on Bowbells in 1985 to no yield in 1988 at the Underwood location. Spring wheat grain yields were generally correlated to total water use. When the topographic factor was added into the regression of yield vs. total water use, the coefficient of determination, R2, increased in the first 3 yr. The last 2 yr of the study were drought years and the topographic factor accurately reflected the lack of water redistribution in those years. Topographic factors measured 15 m from the site gave the highest R2 values.

There is a growing impetus to use soil properties to determine if reclamation efforts are adequate to restore productivity. Constructed mine soils were studied 4 and 11 yr after reclamation to determine physical and hydrological properties. Soils constructed using similar methods and with similar vegetation histories were compared to each other and to an equivalent undisturbed soil. Bulk density was greater in the topsoil and subsoil materials of the constructed soils than in the undisturbed A and B soil horizons. Macropore volume (pore radii > 15 µm) was greater in the topsoil and subsoil materials at the 11‐yr site relative to the 4‐yr site but was significantly lower than that in the undisturbed soil. Small pore volume (pore radii from 4.5 to 0.1 µm) in the reclaimed topsoil materials was similar to the undisturbed A horizon soil but was larger in reclaimed subsoil materials than in the undisturbed B horizon. Saturated hydraulic conductivity (Ks) of the reclaimed topsoil was about 25% that of the undisturbed A horizons and the reclaimed subsoil Ks was less than 10% that of the undisturbed B horizon. The reduction in Ks was attributed to the increase in bulk density and disruption of soil structural units and associated interpedal pore spaces during mining and soil construction. No significant differences in Ks were found between constructed minesoils 4 and 11 yr after reclamation. The results of this study show that soil properties may be useful for evaluating reclamation success after soil construction.

No abstract

Truog P, Bray P, Olsen P, resin P, and surface P were all determined on samples of 17 surface soils from Michigan (from 5 great soil groups), and each soil was cropped in the greenhouse with barley for 4 weeks to determine P uptake and A values. Ca‐P, Al‐P, Fe‐P (by the Chang and Jackson procedure), and organic P were determined on 10 of these soils. Correlation analyses indicate that short‐term uptake of P by barley in the greenhouse was highly correlated with Truog P, while A values, which may be more indicative of seasonal availability, were most highly correlated with Olsen, resin, and Bray P. Organic P and Fe‐P did not contribute to the P removed by any of the measurements. Truog P apparently removed portions of both the Ca‐P and Al‐P fractions, and P removed by cropping was also derived from these two fractions. All the other measurements were highly correlated with only Al‐P.