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Cattle feedlot manure at 0, 90, 180, or 360 metric tons ha‐1 year‐1 was incorporated with Sharpsburg silty clay loam to depths of 10, 20, and 30 cm. For plots tilled 10‐cm deep, the heaviest applications increased the soil organic carbon content from 2 to 5% after 2 years. Particle density decreased from 2.63 to 2.50 g cm‐3 and bulk density decreased from 1.05 to 0.90 g cm‐3. Geometric mean diameter of water‐stable aggregates increased from 80 to 800 µm. Modulus of rupture of soil cores decreased from 0.60 to 0.08 bars. Hydraulic conductivity of undisturbed soil cores increased five fold. Manure applications reduced the hydraulic conductivity of disturbed soils sampled in the fall, but there was no effect on spring samples. The heaviest application of manure increased the electrical conductivity of the hydraulic conductivity leachates from 0.8 to 3.2 mmhos cm‐1 in the fall samples and from 0.4 to 1.2 mmhos cm‐1 in the spring samples. The effects of manure on soil properties decreased with increased depth of tillage.

SUMMARY Chlorella pyrenoidosa Chick (Indiana University Number 252), Nostoc commune Vaucher (I.U. 584), and Oscillatoria prolifica (Grev.) Gomont (I.U. 1270) were grown separately on Peoria loess soil material to measure their effects on the water stability of soil aggregates. Each alga significantly (10% LSD) increased the percentage of soil aggregates after 6 weeks of incubation as compared with the soil without algae. Oscillatoria, Chlorella, and Nostoc increased water stability of aggregates >74 μ in diameter by 3.4, 1.1, and 0.6%, respectively. Nostoc and Oscillatoria produced measurable water stable aggregates in the 1000–2000 μ diameter range; Chlorella formed them in the 500–1000 μ range, while the control soil showed no aggregates >295 μ.

Soil materials were fractionated into 20 separates ranging from 4,760µ to < 2µ in diameter. These separates were packed into splash‐cups and exposed to simulated rainfall intensities of 2 to 12 cm/hr. Raindrops were 5.1 mm in diameter and fell 11.33 m onto the surface of soil materials. Soil particles detached from the surface by the raindrops were oven‐dried and weighted.The amount of detached soil particles from surfaces of all separates was linearly related to simulated rainfall intensity. Linearity was significant at the 0.01 level of probability, except for the coarsest and finest separates. Slope of the line is used to characterize the susceptibility of soil materials to detachment from the surface by raindrops. The slope is measured as milligrams of particles per cm3 of water hitting the surface of soil materials.Detachment of soil particles exposed to simulated rainfall increased from 2.2 mg/cm3 of water for separates 4,760–3,360µ in diameter to a maximum amount of 288 mg/cm3 of water for separates 210–149µ and 149–105µ in diameter. Then, the amount of detached particles decreased with decreasing diameter of particles. Detachment for < 2µ diameter particles was 11 mg/cm3 of water.High‐speed movies showed that splash of raindrops from surfaces of separates > 105µ in diameter consisted of much smaller water drops than from separates < 105µ in diameter. Splash from the surfaces of separates < 105µ in diameter exhibited a crown effect and then broke into smaller drops.

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A field experiment was established to measure the effects of annual applications of high rates of manure for the production of crops under irrigation. The effects of incorporating the manure into the soil by disk plowing to depths of 10 cm, 20 cm, and 30 cm on the stability of the soil mass was measured under simulated rainfall conditions. The effect of simulated rainfall on soil surface compaction as influenced by rate of application of manure and depth of incorporation was measured with a penetrometer.The amount of soil material detached from undisturbed soil cores by simulated raindrops was curvilinearly related to the rainfall intensity. When the plots were disk plowed to a depth of 10 cm, soil detachment increased from 55 mg/cm3 of water for the nonmanured plots to 89 mg/cm3 for the 415 metric tons/ha per year. The amount of soil particles detached by the raindrops was reduced about 15 mg/cm3 of water as the depth of disking the manure into the soil was increased from 10 to 30 cm. Aggregate size distribution of the splashed material showed that prior application of manure to the soil increased the amount of soil aggregates in the large diameter classes. The penetrometer resistance of the crust formed by the waterdrops decreased from 36 kg/cm2 for nonmanured plots to 4.4 kg/cm2 for the plots receiving 360 metric tons of manure/ha/year.

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Sharpsburg silty clay loam was separated into 11 aggregate fractions with the following diameters: 9,250–4,760µ, 4,760–3,360µ, + … +, 297–210µ, and <210µ. Krilium solution was added to half of each aggregate fraction to make the aggregates more water‐stable. The aggregate fractions were packed into splash‐cups and exposed to simulated rainfall intensities from 2 to 12 cm/hr. Raindrops were 5.1 mm in diameter and fell 11.33 m onto the surface of soil materials. Splash of soil particles and aggregates was caught, oven‐dried, and weighed.The amount of detachment of aggregates was linearly related to the rainfall intensity.Detachment of non‐treated aggregates exposed to rainfall increased from 76 mg of particles per cm3 of water to a maximum amount of 172 mg/cm3 as the aggregate diameters decreased from 9,250–4,760µ to 2,360–1,680µ. Then, the amount of detachment decreased with decreasing diameter to aggregate to 78 mg/cm3 for aggregates < 210µ diameter.The addition of Krilium to aggregates reduced the amount of detachment of aggregates >420µ in diameter exposed to simulated rainfall. The amount of splash increased with decreasing diameter of Krilium treated aggregates until 297–210µ diameter was reached (138 mg/cm3), then it decreased (101 mg/cm3) for aggregates < 210µ diameter.