03063naa a2200193 a 450000100080000000500110000800800410001910000220006024501540008226000090023652024650024565000110271065000190272165300140274070000190275470000150277370000160278877300650280418242082025-05-20       1993    bl uuuu     u00u1 u    #d1 aSANTOS, H. P. dos  aEffect of crop rotation on yields, soil chemical characteristics, and economic returns of zero-till barley in southern Brazil.h[electronic resource]  c1993  aThe severe soil degradation and low income problems of producers in southern Brazil are being attributed to the widespread use of wheat ( Tricticum aestivum L. ) -soybean (Glycine max. (L.) Merr. ) or barley (Hordeum vulgare L. )-soybean double-cropping systems, combined with extensive use of mechanical methods of soil tillage. This 6 year study, which was conducted at Guarapuava in southcentral Paramt, compared the effects of four zero-tillage barley rotations on grain yields, soil chemical characteristics, and economic returns. The rotation treatments included: barley-soybean, barley-soybean- vetch (Vicia sativa L.)--corn (Zea mays L.) (1 year without barley), barley-soybean-flax (Linum usitatissimum L. ) -soybean-vetch-corn ( 2 years without barley), and barley-soybean-flaxsoybean- oat (Arena sativa L. )-soybean-vetch-corn (3 years without barley). Yields of barley in the traditional barley-soybean rotation increased by an average of 9% (range of 4-20% higher) by including other winter crops in the rotation, presumably due to a reduction in diseases and pests. Extending the rotation length beyond one winter without a barley crop provided no additional benefit to barley yields. Yields of soybean were lower in several years when grown after flax due likely to allelopathic effects, and after oat due to problems with proper seed placement under the high crop residue conditions. Soil pH and Al concentration tended to revert to the initial levels within 4 years after application of lime. Soil organic matter increased under all rotations reflecting the large amounts of residues being returned to the soil and the low soil losses under zero-tillage management. Costs of production (expressed in US dollars) were highest for the barley-soybean rotation ($ 464 vs. $ 380 ha-1 for mixed rotations). The most profitable cropping system was the 1 year without barley rotation under most economic situations examined. It was profitable to substitute flax or oat for barley when the price ratios of flax to barley and oat to barley exceeded 1.92 and 0.97, respectively. Similarly, it was profitable to substitute corn for soybean during the summer growing season when the price ratio of corn to soybean exceeded 0.39. The traditional barley-soybean rotation displayed the greatest income variability or riskiness. The study concluded that there is both agronomic and economic merit for area producers to adopt these new production opportunities.  aCevada  aPlantio Direto  aRotação1 aZENTNER, R. P.1 aSELLES, F.1 aAMBROSI, I.  tSoil & Tillage Research, Amsterdamgv. 28, p. 141-158, 1993.