The decomposition of cornstalk residue placed on the surface of soil or buried in soil in the field was followed during a corn crop‐growing season by removing from the soil at various times subsamples of decomposing residue contained in glass‐cloth bags. Decomposition during the season (20 weeks) amounted to 50% of the surface residue and 65% of the buried residue. Half of this decomposition occurred in 8 weeks and in 5 weeks for surface and for buried residue, respectively. There was little change in the total N content of surface residue throughout the season. Nitrogen was not immobilized. However, the C/N ratio declined from 57 to approximately 30. A maximum of 12 pounds of N per 3 tons of residue per acre was immobilized by buried residue. This occurred after 3 weeks incubation. Thereafter, total N content of the residue declined. A net loss of N occurred after 5 weeks with no N fertilization and after 15 weeks' with N fertilization. The C/N ratio declined from 57 to 22. The decline in C/N ratio, both with surface and with buried residue, was caused by loss of carbon from the residue rather than an increase in total N. Early season growth of corn plants was retarded by surface residue, but the retardation was not a consequence of N immobilization. A slight retardation of growth with buried residue might, in part, have been caused by immobilization of N.

In the temperature range of 16° to 20°C., a 2°C. differential in soil temperature had a measurable effect on the rate of conversion of NH4‐N to NO3‐N. However, as soil temperature increased to the range of 25° to 30°C. or as the supply of NH4‐N became limiting, differences in NO3‐N production resulting from small differences in soil temperature were not observed. In field soil, very early in the season when soil temperature was in the range of 16° to 20°C., mulched soil was 1° to 2°C. cooler than bare soil. During this period greater accumulation of NO3‐N could occur in bare than in mulched soil as a result of the temperature difference. As measured in the laboratory, NO3‐N production was retarded at soil moisture tensions below 50 cm. of water. At still higher moisture levels, considerable mineral N was lost from the soil. Measurements in the field showed that the soil moisture content of mulched soil exceeded that of bare soil. For short periods of time the moisture level of mulched soil was high enough to cause retarded nitrification and loss of N.

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Synopsis Low nitrogen fertility and the presence of crop residue on the soil surface were coincident with low incidence of rot. Potassium fertilization contributed slightly to decreased disease incidence. All factors that decreased disease incidence were also closely correlated with retarded early growth. Yield was depressed by severe infestation. However, it was impossible to show differential effect of disease on yield as affected by treatment because of interactions of yield, treatment, and disease incidence.

A series of field plots at Clarinda, Iowa, were operated from 1932 through 1963 to study effects of crop and soil management on infiltration, erosion, and crop yield. Major treatment changes were made in 1943 and 1953. Before 1953, soil‐erosion rates were high, especially when corn (Zea mays L.) followed several years of corn, and were inversely related to organic carbon content and aggregate stability of the soil.After the 1953 revision of the study, erosion loss from continuous corn that received annual applications of 179 kg of N per ha (160 lb/acre) were relatively low and were not closely correlated with soil carbon content or with aggregate stability. However, erosion was inversely related to high nitrogen fertility, which, in turn, was accompanied by a trend toward increased soil carbon and high carbohydrate content of the soil. The erosion‐reducing effect of the nitrogen additions were most evident under intense July and August thunderstorms. Soil loss from corn following good meadow was, however, substantially less than from the nitrogen‐treated continuous corn, particularly when erosive rains occurred during the corn seedling stage of the crop year. Crop yield was directly related to N fertility and not to aggregate stability or to organic‐matter content of the soil.