A soil quality (SQ) assessment and rating framework that is quantitative, iterative, and adaptable, with justifiable weighting for quality scores, is required for evaluating site-specific SQ at land reclamation sites. Such a framework needs to identify the minimum dataset that reflects the current knowledge regarding relationships between SQ indicators and relevant measures of ecosystem performance. Our objective was to develop nonlinear scoring functions for assessing the impact on SQ of peat-mineral mix (PMM) used as a cover soil at land reclamation sites. Soil functional indicators affected by PMM were extracted from existing databases and correlated with soil organic carbon (SOC). Based on defined objectives for SQ assessment, indicators with significant correlation ( < 0.05) to SOC were selected, normalized, and fitted to sigmoid functions using nonlinear regression procedure to establish SQ functions (SQFs) that can analyze changes in field capacity, permanent wilting point, soil nitrogen, and cation exchange capacity of PMM using SOC as input parameter. Application of the SQFs to an independent dataset produced ratings with mean differences similar to the treatment effects of mixing three levels of peat and mineral soil. These results show that derived ratings and weighing factors using SOC reflect the relationship between PMM treatment and other SQ indicators. Applying the developed SQFs to a long-term soil monitoring dataset shows that an increase or decrease in SOC from 10 to 20 g kg causes a significant change in SQ. This identifies the need for further nutrient and moisture management of PMM to support long-term SQ development in land reclamation.

The objective of this experiment was to determine the movement of different forms of phosphorus (P) in a clay loam soil with 33 years of manure application at the rate of 0, 30, 60 and 120 Mg ha -1 yr -1 . Soil samples were taken from 3 soil layers and subjected to leaching in packed soil column. Leachate was analyzed for total (P t ), inorganic (P i ) and organic P (P o ). Inorganic P accounted for about 70% of leachate P t . About 50% of P t in leachate was lost within the first 5 pore-volume (PV). While 2% of soil total P was lost in 20 PV of leachate from the control soil, 5-7% was lost from the manure amended soil. The amount of P lost in the leachate increased with the rate of manure application but decreased with soil depth. This column leaching study showed that P could be lost through leaching especially at high rate of manure application. Irrigation activity enhanced in situ movement of P down the soil profile.

Corn (Zea mays L.) stover harvest must be balanced against protecting soil properties, including water-stable aggregates (WSA). The formation and maintenance of WSA functions of multiple factors including management. Harvesting stover alters the mass of the residue retained, which might alter a soil's ability to form and maintain WSA. A study was conducted on two independently replicated fields under chisel plow (CP) and no-till (NT) management, both in a corn-soybean [Glycine max.(L.) Merr.] rotation with four corn residue retention treatments (RRT): [harvesting only grain, grain plus cobs, grain plus about half the stover, and grain plus as much stover as possible (Grain + Aggressive)], returning about 8, 5, 4 and 2 Mg ha −1 yr −1 dry stover, respectively. Water-stable aggregates, their distribution, and mean weight diameter (MWD) were determined on a clay loam or loam Mollisol collected at 0 to 5 and 5 to 10 cm. Treatments, crop phase, soil depth, and their interactions were analyzed via a mixed linear model. Linear regression was used to assay the relationships between WSA and the average mass of residue returned. In both fields, Grain + Aggressive had the lowest WSA and MWD, and fewer ≥2-mm aggregates than other RRTs and, in the NT field, fewer in the 1-to 2-mm class size as well. Overall, WSA increased by 0.85 and 2.25% per Mg stover returned under CP and NT, respectively.Harvesting stover reduced the formation and/or the maintenance of WSA, thereby reducing their ability to resist the erosive force of water.

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