Crop rotations and soil-management practices on a random sample of mixed crop and livestock properties on the North- Western Slope were discussed in the last issue of this journal. The survey on which the latter article was based was carried out in March, April and May, 1952, and seventy-six farmers were visited in the shires of Peel, Liverpool Plains, Macintyre and Yallaroi. As the survey was concerned mainly with practices on wheat farms, the sample was drawn from important wheat-growing districts in different parts of the North Western Slope. The first article included an analysis of the influence of the size of farms and different soil types on the cropping practices adopted throughout the area. In order to compare the practices of holdings of different size groups, farms of 600 acres, or less, arable, and of a total area not exceeding 1,000 acres, were classed as "small" farms and the remainder as "large" farms. A significant relation was found to exist between the crop rotations followed on farms in these two size-groups, ninety per cent. of the small holdings having a rotation of one-year in-two, or shorter, compared with fifty-five per cent. for the large properties. It was also found that higher incomes in recent years, largely due to higher wool prices, have enabled farmers, especially those on small holdings, to introduce wider crop rotations and other soil conserving practices.

The purpose of this study was to determine some changes that have taken place in the surface of cultivated soils. Permeability, volume weight, and percent of pores drained were determined on virgin soils, fertilized and unfertilized soils, soil farmed to a good rotation in contrast to a poor rotation, and eroded soils as compared to slightly eroded soils. Some studies were also made on the effect of cultivation on percent aggregation. Six different soils were studied in the state. Undisturbed core samples were taken at random with a steel cylindrical sampler and analyzed for permeability, volume weight, and pores drained. Most samples were taken from corn fields in the fall of the year. Infiltration values for soil with various mulch covers were secured in the field with a type F infiltrometer. The surface of most soils was originally moderate to moderately rapid in permeability. The addition of limestone and fertilizers has increased the permeability rate of the soil as compared to the untreated plots. This response may be attributed to increased growth of plants. The percentage of large aggregates (1.0 mm) in the surface soil of cultivated areas was reduced from 4 to 20 times as compared to virgin areas. Surface samples taken from plots farmed to a corn, oats, clover, wheat (clover) rotation were 16 times more permeable and held 17% more available water than samples taken from plots farmed to a corn, corn, corn, soybean rotation. Severely eroded soils were less permeable than moderately eroded soils. Wheat straw and crop residues increased infiltration rates approximately three times as compared to bare ground, no mulch.

Comparative decomposition rates of alfalfa, wheat straw, and whole partridge pea, or its various plant parts taken separately, were determined by measuring weight losses during laboratory incubations. Effects of these plant materials on nitrification rates in soil were also determined. The alfalfa lost the most weight by decomposition during a 32-week period. The loss in weight of straw also exceeded that of the whole plant of partridge pea. The nitrification rate with partridge pea added was lower than that with untreated soil. Partridge pea leaves increased nitrification, but the pods or stalks decreased it. The nitrate content of field plots previously grown to partridge pea was higher than that of plots without a legume, but not as high as in plots previously in sweet clover.

Organic phosphorus compounds contain a large portion of the total phosphorus in many soils. The release of phosphate from the organic form is thought to be enzymatic in nature. Since clays compose an active and important part of the soil, a study was made of their effect on the enzymatic hydrolysis of several organic phosphorus compounds. The effect of clays on the enzymatic hydrolysis of fructose-diphosphate, phytin, glycerophosphate, and lecithin was studied. The enzymes were prepared from bread yeast, wheat bran, bread yeast, and kidney cortex, respectively. The various clays studied included kaolinite, Wyoming bentonite (montmorillonite), Swygert (illite), and Cisne (a clay similar to Putnam). The activity of the enzyme was determined with no clay present, and then in the presence of various amounts and kinds of clays. The enzymatic reactions were performed paying special attention to the control of pH, temperatures, inhibitors, activators, and concentrations. The difference between the activity of the enzyme on the organic phosphorus compound in the presence of a suitable buffer and the activity in the presence of clays was considered a measure of the influence of the clay upon the enzyme activity. All of the clays used in this study exhibited an inhibiting influence upon the enzymatic hydrolysis of the organic phosphorus compounds. The amount of inhibition varied with the kind of clay according to the following series: Wyoming bentonite (montmorillonite) > Cisne (Putnam-like clay) > Swygert (illite) > kaolinite. The inhibition of phosphatase activity by clays is roughly proportional to the base exchange capacity of the clay. A constant, evaluated for each clay in an empirical equation which describes hydrolysis of the organic compound in the presence of varying quantities of clay, is approximately equal to the ratios of the base exchange capacities of the various clays. The study indicates that the inhibition is due to the effect of the clay on the enzyme and not to adsorption of the organic phosphorus compound by the clay.