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Chisel tillage to alleviate soil compaction problems is known to provide significant benefits, but the required frequency of chisel tillage is not known. This study was designed to seek information on the required frequency of chisel tillage in moderately and severely eroded soils, using penetrometer cone index and water infiltration rate to quantify soil condition and a paratill as the chiseling tool. The cone index and water infiltration results indicated that in either the moderately or severely eroded soils used in this study, chiseling needs to be conducted annually, especially on severely eroded soils, to ensure minimizing the effect of soil compaction on crop growth.

Cone index measurements of experimental field plots after eight years of three constant traffic-tillage systems showed low variability in soil zones unaffected by tillage or traffic. There were significant differences in cone index in soil zones directly affected by tillage and traffic. The results support the concept that much of the variability in cone index under field conditions is caused by tillage and traffic as opposed to soil heterogeneity. The results imply that by taking closely spaced samples, and having a knowledge of how cone index relates to traffic and tillage, the previous traffic-tillage history of a soil can be assessed.

SOIL erosion control of row-cropped, Southern Piedmont lands is a constant problem. A 2.71 ha (6.70 acre) watershed, with an average slope of 3.4 percent, was equipped with a 0.76 m (2.5 ft) H-flume in summer of 1972 to study runoff and soil losses from row crop land. The watershed treatments were con-ventional till, without terraces or grassed waterways, during the first 2 yr in a soybean {Glycine max (L.) Merr.)-fallow sequence, and then 2 yr of no-till double cropped barley (Hordeum vulgare L.), followed by grain sorghum {Sorghum vulgare Pers.) with fescue {Festuca arundinacea Schreb) grassed waterway. Annual runoff was decreased from 22.5 cm (17.6 percent) with con-ventional tillage to 12.0 cm (9.7 percent) with double cropped, no-till practices. Runoff was reduced 90 percent during the vulnerable sediment and chemical transport season of May, June, and July. Annual flume-measured sediment decreased from 26.26 t (metric tons)/ha (11.71 tons/acre) with conventional tillage to 0.13 t/ha (0.06 ton/acre) with no-tillage. Soil loss values associated with no-tillage show that crop row direction is not important when no-tilling is accom-panied with grassed waterways in the Southern Piedmont. Barley and grain sorghum both produced 15.43 t/ha (6.88 tons/acre) of grain during the no-till period. Annual erosion, estimated by the Wischmeier-Smith erosion equation (WSEE), was 71.23 t/ha (31.80 tons/acre) and 1.30 t/ha (0.58 ton/acre) for conventional and no-till, respectively.

PRACTICAL application of seasonal risk analysis for soil conservation planning is illustrated. Applicability is demonstrated by quantifying potential reduction in soil loss through seasonal adjustment of agronomic practice. The method is dependent upon seasonally continuous probability distributions developed earlier. The erosion index (EI) and the cover and management factor (C) of the Universal Soil Loss Equation were selected to quantify soil loss calculations. By randomizing these two variates soil loss by both seasonal pattern and annual total was simulated for 12 different agronomic practices. Reduction of soil loss was expressed in terms of expectation (risk) and in terms of variability of that expectation (uncertainty). Utilizing the simulated soil losses the utility of incorporating seasonal variability in management options to facilitate conservation planning is demonstrated.