Living mulch is a cover crop which is intercropped with a cash crop to protect against soil erosion and structural deterioration without taking land out of production. To avoid interference which reduces cash crop yield, the mulch requires management techniques which minimize resource utilization during the critical period of crop development without killing the mulch outright. The experiments reported here examine non-chemical management innovations in a sweet corn-white clover intercrop system which allow for clover regrowth and also contribute to the N requirement of the corn. In 1986 clover was suppressed by mowing or partial rototilling. Yields of corn in plots where clover was rototilled were comparable to yields of clean cultivated corn and superior to yields from plots where clover was mowed or unsuppressed. In 1987 rototilling was compared at 3 timings after corn emergence. Highest corn yields were obtained by rototilling the well-established clover at 2 rather than 4 or 6 weeks after emergence. Yields from rototilled plots in 1987 exceeded those from clean cultivated plots or plots where clover was unsuppressed. After rototilling, the clover reestablished via stoloniferous growth emanating from a narrow strip of roots which passed between the tiller tines. In both years corn leaf N concentrations were highest in the rototilled plots. In 1987 clean cultivated corn appeared N deficient and had a greater incidence of corn smut than corn from the rototilled clover plots. Multiple corn row arrangements which facilitate access to the mulch were compared at a constant plant population to conventional single rows on 76 cm centers. There were no differences in yield between single and double rows (152 cm centers) in either year, while the triple-row arrangement (228 cm centers) reduced yield in 1987 due to the low productivity of the plants in the middle row of the 3 rows.

Underestimation of the pivotal role played by managed and native insect pollinators is a key constraint to the sustainability of contemporary agricultural practices. The economic value of such insects to pollination, seed set, and fruit formation greatly outweighs that suggested by more conventional indices, such as the value of honey and wax produced by honeybees. Although the European honeybee has been widely regarded as the single most important pollinating species, the increasing spread of trachael and Varroa mites and Africanized bees threatens the distribution and magnitude of traditional honeybeekeeping enterprises in North America. A number of other bee and insect pollinators, such as orchard bees, bumblebees, and squash bees, which are not affected by either the mites or the Africanized bees, are considered as likely candidates for management and use in commercial agriculture. An additional role can be played by native or wild pollinators, provided that attention is given to curtailing of population losses caused by both inadvertent insecticide poisoning and habitat destruction. To ensure a reliable source of pollinators, both managed and native, a more comprehensive strategy for management of crop pollination is needed. Elements of this strategy include an increased understanding of the biology and ecology of pollinating insects, as well as providing appropriate nesting habitat, and ensuring the availability of alternative sources of “forage” to sustain populations when the target crops are not in bloom. Examples are discussed to illustrate how private initiatives and changes to public policy can enhance pollinator habitat, and ultimately, agricultural productivity.

In the fifth year of an agricultural conversion experiment in Pennsylvania, we studied the soil biological community under three treatment regimes planted with corn: organic-manure, organic-legume, and a conventional system. The organic treatments consisted of complex crop rotations, cultivations, and organic matter inputs to control pests and maintain soil fertility. The conventional system consisted of a simple corn/soybean rotation with synthetic fertilizer and pesticide inputs. High rates of CO2 evolution (a measure of potential microbial activity) in the organic plots corresponded with high levels of organic matter input. Soil nematodes were most abundant in organic plots, although seasonal patterns differed between the two organic treatments. Soil microarthropods were dominated by fungivorous Prostigmata mites, which reached peak abundance in organic plots two to five months after organic matter incorporation. Oribatid mites, which were rare throughout the study, followed the same pattern of abundance in each treatment and were probably most influenced by tillage disturbances. Predatory Mesostigmata were generally more abundant in organic plots. Surface-dwelling Collembola were abundant briefly in the spring, but soil-dwelling species dominated numerically throughout the cropping season. Spring tillage appeared to have a strong negative effect on earthworm populations in all plots. Small earthworm species became abundant in organic-manure plots during the summer. Larger earthworm species were abundant in organic-legume and conventional plots after the autumn harvest, when crop residues covered the undisturbed soil The systems-level nature of the Conversion Project experiment makes it difficult to identify cause-effect relationships. The data do suggest that organic amendments tend to enhance soil biological activity, while tillage disturbances tend to disrupt the biotic community.

Afield study was conducted between 1972 and 1982 to compare the effects of previous crop on row crop yields under rainfed conditions in eastern Nebraska. The objectives were to determine the effects of fallow and three previous crops: corn (Lea. maysLJ, soybeans /Glycine max (L.) Mem], and grain sorghum /Sorghum bicolor (L.) Moench], on the growth and grain yield of the same crops. The study was conducted on a Sharpsburg silty clay loam (fine, montmorillonitic, mesicf Typic Argiudoll). Corn grain yield was most variable (C. V. 23.4percent) compared to soybean (C. V. 13.6percent) or grain sorghum (C. V. 9.5 percent) yields. Corn was also the most sensitive crop to previous crop effects. The range of treatment yields for each crop was 47 percent, 22 percent, and 11 percent of the overall means for corn, soybean, and sorghum, respectively. Previous crop affected yields for all crops, but the effects were not consistent across years. All crops produced highest yield following fallow. Yields of corn, soybean, and grain sorghum following fallow were 74, 25, and 10 percent higher than their respective monoculture yields. In years of average precipitation, a corn-soybean sequence produced the greatest yield. In years having above- or below-normal precipitation, a grain sorghum-soybean sequence produced the highest yield.

Phosphorus (P) accumulation and use efficiency by broccoli (Brassica oleraceae var. italica) were observed in a field plot study comparing management with varying levels of conventional fertilizer, differing composted amendments, and a combination of inorganic Nitrogen (N) and compost sources. Total P accumulation and yield were highest in treatments incorporating solely compost or vermicompost applications of 30 tons ha–1. Applications of N as ammonium sulfate caused significant soil acidification, which lowered yield and P uptake. Poor growth and yield were probably related to manganese toxicity effects on root extension and activity. These effects were partly ameliorated in treatments combining fertilizer N and compost sources. As a result, yield in plots receiving 75 kg N ha–1 as ammonium sulfate and 8.9 kg P ha–1 as compost was nearly identical to highest experimental yields. Phosphorus use efficiency was highest in this treatment incorporating fertilizer N and compost. Generally, P use efficiency tended to decline at the highest levels of fertilization. We propose that intensive organic matter management may be a good way to improve P use efficiency by vegetable crops.