The role of soil surface crusting in desertification and strategies to reduce crusting.

Soil crusting decreases infiltration, increases erosion, and impedes vegetation establishment, so reducing the impact of crusting is of major importance in combating desertification. Although surface crusting has been the subject of considerable research over the past 50 years or more, the practical management of soil crusts remains a challenge for many dryland communities. Crusting occurs in two steps, an initial aggregate breakdown period that occurs under rainfall and a subsequent hardening phase during drying. Several factors influence crust development, but the single most important one is soil aggregate stability. Strategies to reduce crusting can be based either on protecting the surface from raindrop impact or improving aggregate stability, or a combination of both. However, crust control is labor and/or capital intensive and must be thought out clearly in terms of the benefits to be achieved.

Sorption of atrazine and metolachlor by burrow linings developed in soils with different crop residues at the surface.

Atrazine and metolachlor sorption by earthworm (Lumbricus terrestris L.) burrows was measured by introducing herbicides into the burrows and collecting the effluent between 0 to 3, 3 to 6, and 6 to 9 min of simulated burrow flow. On average, sorption by burrow linings reduced the herbicide concentration to 78% (atrazine) and 74% (metolachlor) of the applied herbicide solution concentration. For both herbicides, the amount sorbed was dependent on the food source available to the earthworm, as well as the duration of burrow flow. On average, soybean-fed- and corn-fed-earthworm-burrows significantly retained more herbicides relative to the Control Treatment (unfed-earthworms). More herbicides were transported through the burrows with time because the lateral flow movement from the burrow wall into the soil matrix decreased. It is also likely that herbicides retained on burrow linings during the first 3 min of flow saturated the adsorption sites on the burrow wall, which decreased the subsequent retention potential of herbicides in flow between 3 to 9 min. Based on these results, we conclude that herbicide transport through earthworm burrows in the field will be related to crop and crop residue management practices.

Medical evaluation of the special supplemental food program for women, infants, and children.

The special supplemental food program for women, infants, and children administered by the United States Department of Agriculture, was evaluated nationally. Participating infants, children under 4 years old, and pregnant and nursing women were investigated initially, and after receiving food supplements. The supplements were iron-fortified infant formula, iron-fortified infant cereals, and fruit juices for the infants, and milk, cheese, iron-fortified cereals, eggs, and fruit juices for the children and women. Initially, the average birth weight was lower and the infant mortality rate was higher than expected in a well nourished population. There was also evidence of slight growth retardation, a high anemia rate, and a high percentage of participants having saturation of transferrin values less 15%. The program had no effect on the prevalence of unsatisfactory values for saturation of transferrin. There was an increase in weight gain during pregnancy, and increase in birth weight, an acceleration of growth, and a reduction in the anemia rate in all participant categories except women in the first and second trimesters of pregnancy.