Recovery of fertilizer N by three successive corn (Zea mays L.) crops and as inorganic N in the soil profile following the last crop ranged from 72 to 88%. Total amount of NO3‐N in the soil profiles was directly related to the rate of N application and to the frequency of corn in the rotation. More leaching of NO3‐N generally occurred between fall and spring samplings than during the growing season. The most effective methods indicated for limiting the amounts of NO3‐N passing through the soil profile to the water table include: limiting rates of N fertilizer to approximately that required by the crop, reducing the acreage and frequency of corn or other crops that received fertilizer N in the rotation, and maintaining a crop cover on the land as much of the time as is feasible.

The relative importance of diverse factors affecting aggregation in four Wisconsin soil types was studied by multiple regression analyses. Single and combined effects of pH and contents of organic matter, microbial gum, clay, and free iron oxide were considered. In general the most important single factor was the microbial gum. However, in the Kewaunee soil which has a relatively high content of clay and iron oxide, the iron oxide was of prime importance in aggregate formation. In all the soils, iron oxide showed a marked effect on aggregation with a tendency to be more important in the smaller aggregate size range. The effect of clay, however, was very small with the exception of the high clay soil (often > 30% clay), in which its effect was only exceeded by that of the free iron oxide. In the multiple correlation analysis the effect of organic matter was considered separately from that of microbial gums. By this statistical analysis only a slight positive relationship existed between organic matter and soil aggregation, i.e., the effect of organic matter was conditioned largely by its content of microbial gum; pH 6.5 was optimum. No relationship existed between soil aggregation and the rate of decomposition of organic matter as measured by CO2 evolution from the soil.

Incubation and greenhouse studies showed that regardless of soil pH, flooding increased the content of exchangeable Mn and the Mn content of alfalfa (Medicago sativa L.) grown in a Kellner loamy sand. In the absence of a source of easily decomposable organic matter, Mn mobilization by flooding was considerably slower at a soil pH of 4.7 than at 7.3. Where alfalfa was grown in the soil or where finely milled oat straw was added, flooding mobilized more Mn in the acid than in the neutral soils. Liming promoted immobilization of Mn on the resumption of normal soil moisture relations after flooding. Seventy-two hours of flooding increased the Mn content of the alfalfa on the unlimed soil from 426 ppm to more than 6,000 ppm. Excess Mn tended to accumulate in the leaves and growing points of the plants. The results suggest that the well-known susceptibility of alfalfa to Mn toxicity may also account for its sensitivity to poorly aerated soils.

HE growing of alfalfa in certain areas of the northern T half of Wisconsin has been rather unsuccessful because of winterkilling. Consequently, the hay produced in that part of the state is often mostly timothy with some clover, and is therefore comparatively low in feeding value. Fortunately, recent experiments in these areas have shown that good crops of alfalfa can be grown, and winterkilling practically eliminated by proper lime and .fertilizer treatments. The main purpose of the present investigation was to determine how these treatments affect the chemical composition of the alfalfa plant so as to promote its ability to withstand winter injury, and thus continue to give satisfactory yields.

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