The objective of this work was to identify soil parameters potentially useful to monitor soil quality under different soil management and crop rotation systems. Microbiological and chemical parameters were evaluated in a field experiment in the State of Parana, southern Brazil, in response to soil management [no-tillage (NT) and conventional tillage (CT)] and crop rotation [including grain (soybean, S; maize, M; wheat, W) and legume (lupin, L.) and non-legume (oat, O) covers] systems. Three crop rotation systems were evaluated: (1) (O/M/O/S/W/S/L/M/O/S), (2) (O/S/L/M/O/S/W/S/L/M), and (3) (O/S/W/S/L/M/O/M/W/M), and soil parameters were monitored after the fifth year. Before ploughing, CO2-emission rates were similar in NT and CT soils, but plough increased it by an average of 57%. Carbon dioxide emission was 13% higher with lupin residues than with wheat straw; decomposition rates were rapid with both soil management systems. Amounts of microbial biomass carbon and nitrogen (MB-C and MB-N, respectively) were 80 and 104% higher in NT than in CT, respectively; however, in general these parameters were not affected by crop rotation. Efficiency of the microbial community was significantly higher in NT: metabolic quotient (qCO2) was 55% lower than in CT. Soluble C and N levels were 37 and 24% greater in NT than in CT, respectively, with no effects of crop rotation. Furthermore, ratios of soluble C and N contents to MB-C and MB-N were consistently lower in NT, indicating higher immobilization of C and N per unit of MB. The decrease in qCO2 and the increase in MB-C under NT allowed enhancements in soil C stocks, such that in the 0–40 cm profile, a gain of 2500 kg of C ha−1 was observed in relation to CT. Carbon stocks also varied with crop rotation, with net changes at 0–40 cm of 726, 1167 and −394 kg C ha−1 year, in rotations 1, 2 and 3, respectively. Similar results were obtained for the N stocks, with 410 kg N ha−1 gained in NT, while crop rotations 1, 2 and 3 accumulated 71, 137 and 37 kg of N ha−1 year−1, respectively. On average, microbial biomass corresponded to 2.4 and 1.7% of the total soil C, and 5.2 and 3.2% of the N in NT and CT systems, respectively. Soil management was the main factor affecting soil C and N levels, but enhancement also resulted from the ratios of legumes and non-legumes in the rotations. The results emphasize the importance of microorganisms as reservoirs of C and N in tropical soils. Furthermore, the parameters associated with microbiological activity were more responsive to soil management and crop rotation effects than were total stocks of C and N, demonstrating their usefulness as indicators of soil quality in the tropics.

Microbiological parameters as indicators of soil quality under various soil management and crop rotation systems in southern Brazil

The no-tillage system with grain crops occupies today 2.5 millions hectares in the state of Parana. Besides the traditional rotation system with wheat and soybean, in many areas green manure cover crops are also sown in the Winter and corn in the Summer. The objective of this study was to evaluate changes in some of the soil chemical properties after eight years under the crop rotation systems: wheat-soybean-black oat-soybean (WOS), wheat-soybean-lupine-corn-black oat-soybean (LCO), lupine-corn-wheat-soybean (LC) and compare them with the traditional system wheat-soybean (WS) grown in two Oxisols at Londrina and Campo Mourao, State of Parana, Brazil. The LC crop rotation system reduced the soil pH and the level of exchangeable calcium (Ca2+) and magnesium (Mg2+) and increased the excangeable aluminum (Al3+), the potential acidity (H + Al), and the total-N in the soil as compared to the WS system. These characteristics showed intermediate values in the other systems. There were no significant differences on soil levels of organic carbon and exchangeable-K (K+) among the crop rotation systems. The decrease on the level of Ca2+ in the LC system was larger than the amount of Ca applied as lime to the soil during the experiment. Soil acidification was related to the nitrogen fertilization of wheat and corn. The maintenance of levels of K+ and the decrease on the levels of Ca2+ and Mg2+ demonstrate that there was a change in the preference of leaching cations in the LC crop rotation system. The formation of metal-organic complexes with divalent cations was assumed to be the possible mechanism responsible for the chemical alterations in the soil.

/pdf/alteracoes-na-fertilidade-do-solo-em-sistemas-de-rotacao-de-fa8viquk8n.pdf

Alterações na fertilidade do solo em sistemas de rotação de culturas em semeadura direta

The impact four cultivation systems on the soil fauna was studied, using Oribatida and Gamasida acarids as bioindicators and collembolan. The research was carried out in experimental fields, located in EMBRAPA - CPAO in Dourados, Centerwest of Brazil from July 1997 to December 1999. The constant pasture system presented smaller impact on the soil fauna followed by agricultural cattle rotation and a direct plantation system. In the conventional plantation series, the populational density of the mesofauna organisms was low, especially collembolan families.

/pdf/study-of-acari-and-collembola-populations-in-four-129uctqihz.pdf

Study of Acari and Collembola Populations in Four Cultivation Systems in Dourados - MS

Decomposition of plant residues used in no-tillage systems as revealed by flash pyrolysis

The effects of soil tillage and crop rotation on humic substances of an Oxisol from southern Brazil were studied. Soils were sampled from conventional (CT) and no-tillage (NT) systems applied to soybean-wheat (S-W) and soybean-lupine-maize-wheat (S-L-M-W) rotations. Two additional samples from soils with secondary forest and eucalyptus were collected. Humic substances (HS) were extracted by chelating ion exchange resin and water. Grey humic acids (GHA), brown humic acids (BHA) and fulvic acids (FA) were analysed chromatographically on controlled pore glass. As expected, cultivation and tillage led to a decrease in soil organic carbon content. This diminution was somewhat lower in conventional tillage with S-L-M-W, compared with S-W rotation. The total amount of extractable HS was higher for forest soils. Cultivated soils with both CT and NT showed higher contents of GHA than BHA and FA. Crop rotation had an important influence on the quality of the organic matter as the S-W rotation with both CT and NT showed the highest GHA contents. Soils with eucalyptus exhibited the highest amount of extractable humic substances among the investigated soils.

Tillage and crop rotation interactions on humic substances of a typic haplorthox from southern Brazil

Em ensaio de longa duracao, o IAPAR realiza pesquisa multidisciplinar, desde 1976, em areas com diferentes caracteristicas edafoclimaticas, no Estado do Parana. Os objetivos sao: a) comparar o plantio direto com o convencional, em rotacoes de culturas, quanto a produtividade e rentabilidade; b) avaliar os efeitos dos sistemas de cultivo e das rotacoes de culturas na ocorrencia de ervas daninhas, pragas e molestias; e) definir alternativas de rotacoes de culturas para o plantio direto. No periodo de 1976 a 1980, o milho ( Zea mays L.) em plantio direto evidenciou: maior velocidade de emergencia, crescimento inicial mais uniforme e vigoroso e menos danos por acamamento; maior indice de quebramento de colmos e reducao na produtividade de graos, por deficiencias de nitrogenio mais acentuadas, com diminuicao desses efeitos na rotacao com soja; maior ocorrencia de ervas daninhas e maior incidencia de podridao do colmo; menor consumo de oleo diesel e maior consumo de herbicidas. Na media de quatro safras consecutivas, os rendimentos de graos foram similares e os custos variaveis de producao nao diferiram significativamente entre os sistemas de cultivo. A alternância de milho com soja na rotacao com trigo proporcionou melhor resultado economico comparado com a rotacao continua de soja com trigo.

/pdf/comportamento-e-possibilidades-da-cultura-do-milho-em-55rswhcpaz.pdf

Comportamento e possibilidades da cultura do milho em plantio direto no Estado do Paraná

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Comportamento e possibilidades da cultura do milho em plantio direto no Estado do Paraná