Soil chemical and physical parameters under no-tillage in crop production systems with winter annual pastures.
Abstract
Soi I physical and chemical parameters were evaluated on os ley farming crop systems in a typical dystrophic Red Latosol (Typic Haplorthox) located in Passo Fundo, Statc of Rio Grande do Sul, l3razil, atter six years (1990/91 to 1995/96) of four production systems under no-til lagc: system I (wheat/soybcan, black oat pasture/soybean and black oat pasture/soybcan); system 11 (wheat/soybean and black oat + common vetch pasture/com); system 111 (wheat/soybean, black oat + common vetch pasturc/soybean and black oat + common vetch pasturekorn); and system IV (wheat/soybean, oat/soybcan and oat/soybcan). Neither the valucs of p1-1, exchangcable AI, and Ca + Mg nor the physical parameters studicd were influenccd by the crop production systems. Howcver, the system IV showed highcr leveis of organic matter in the 10-20 cm layer, when compareci to the systcns I and II. Extractable P content was higher in the system IV than in the systems 11 and 111, in the 0-5 em layer, while exchangcable K was highcr in the systens IV, comparatively to the systcns I, II, and III, in ali laycrs studied. For the crop production systems valucs higher than the oncs originally recorded were obscrvcd ia the leveis of soil organic matter, extractable P, and exchangcable K, mainly in lhe 0-5 cm layer, in May 1996. Organic matter Icvels and the contents ofexchangcable Ca +Mg, extractablc P, and exchangeable K in the 0-5 cm layer %vero 1.1 to 1.2, 1.3 to 1.4. 4.2 to 4.6, and 2.6 to 3.3 times greater than the ones found ia the 10-20 cm layer, respectively. Soil bulk density presents higher values from the superface layer in ali crop systems as results of soil compaction. Percent of watcr stablc aggregates with diameter cxceeding 4.76 mm and geometric mcan diameter of aggregates were higher in the surfacc layer duc to aggegatin promoted by soil organic matter. There is no evidente that caule weight load aggavated the compaction problem. Annual winter pasture crops did not favoRing reduction ofsoil compaction.
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