Effects of conversion to organic agricultural practices on soil biota

• Published in: American journal of alternative agriculture 1990-03, Vol.5 (1), p.24-32
• Main Authors: Werner, Matthew R., Dindal, Daniel L.
• Format: Article
• Language: English
• Subjects: ACARINA; Agricultural soils; Agrology; AMENDEMENT DU SOL; BIOTA; BIOTE; COLLEMBOLA; Earthworms; ENMIENDAS DEL SUELO; FAUNA DEL SUELO; FAUNE DU SOL; Forest soils; LABRANZA; LUMBRICIDAE; MATERIA ORGANICA; MATIERE ORGANIQUE; microarthropods; Mites; NEMATODA; nematodes; Organic farming; ORGANIC MATTER; organic soil amendments; Organic soils; POROSITE DU SOL; SISTEMA POROSO DEL SUELO; SOIL; SOIL AMENDMENTS; Soil ecology; SOIL FAUNA; Soil nematodes; SOIL PORE SYSTEM; soil respiration; SOL; SUELO; TILLAGE; TRAVAIL DU SOL
• ISSN: 0889-1893; 1478-5498
• DOI: 10.1017/S0889189300003192

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.