Soil respiration in cucumber field under crop rotation in solar greenhouse

Crop residues are the primary source of carbon input in the soil carbon pool. Crop rotation can impact the plant biomass returned to the soil, and influence soil respiration. To study the effect of previous crops on soil respiration in cucumber (Cucumis statirus L.) fields in solar greenhouses, soil respiration, plant height, leaf area and yield were measured during the growing season (from the end of Sept to the beginning of Jun the following year) from 2007 to 2010. The cucumber was grown following fallow (CK), kidney bean (KB), cowpea (CP), maize for green manure (MGM), black bean for green manure (BGM), tomato (TM), bok choy (BC). As compared with CK, KB, CP, MGM and BGM may increase soil respiration, while TM and BC may decrease soil respiration at full fruit stage in cucumber fields. Thus attention to the previous crop arrangement is a possible way of mitigating soil respiration in vegetable fields. Plant height, leaf area and yield had similar variation trends under seven previous crop treatments. The ratio of yield to soil respiration revealed that MGM is the crop of choice previous to cucumber when compared with CK, KB, CP, BGM, TM and BC

Effects of different management systems on porosity of oxisols in Paraná, Brazil Porosidade de latossolos do paraná influenciada por diferentes manejos

Soils play a fundamental role in the production of human foods. The Oxisols in the state of Paraná are among the richest and most productive soils in Brazil, but degradation and low porosity are frequently documented, due to intensive farming involving various management strategies and the application of high-tech solutions. This study aims to investigate changes in the porosity of two Red Oxisols (Latossolos Vermelhos), denoted LVef (eutroferric) and LVdf (dystroferric) under conventional and no-tillage soil management, with a succession of annual crops of soybean, maize and wheat over a continuous period of more than 20 years. After describing the soil profiles under native forest, no-tillage management and conventional tillage using the crop profile method, deformed and non-deformed soil samples were collected from the volumes most compacted by human intervention and the physical, chemical and mineralogical properties analyzed. The various porosity classes (total pore volume, inter-aggregate porosity between channels and biological cavities) and intra-aggregate porosity (determined in 10 cm³ saturated clods subjected to a pressure of -10 kPa to obtain a pore volume with a radius (r eq), > 15 &#956;m and < 15 &#956;m). The results showed that the effects of no-tillage farming on porosity are more pronounced in both soil types. Porosity of the LVdf was higher than pf the LVef soil, whatever the management type. In the LVdf soil, only pores with a radius of > 15 &#956;m were affected by farming whereas in the LVef soil, pores with a radius of < 15 &#956;m were affected as well.<br>Sabe-se que os solos têm função primordial na produção de alimentos para a humanidade. No Estado do Paraná, os Latossolos Vermelhos estão entre os mais produtivos do Brasil; devido à utilização intensa deles com diferentes práticas culturais e a uma agricultura altamente tecnificada, são comuns relatos de sua degradação física, com redução da porosidade. Dessa forma, o objetivo deste trabalho consistiu em estudar a modificação da porosidade de Latossolos Vermelho eutroférrico (LVef) e distroférrico (LVdf) cultivados sob plantio direto e convencional, com sucessão das culturas anuais soja, milho e trigo por mais de 20 anos consecutivos. Após uma descrição dos perfis de solo sob mata, plantio direto e preparo convencional pelo método do perfil cultural, coletaram-se amostras de solo deformadas e indeformadas nos volumes de solo antropizados mais compactos, para as análises físicas, químicas, mineralógicas e estudo das diferentes classes de poros (volume total de poros, poros entre (canais e cavidades biológicas) e intra-agregados (determinada em torrões de 10 cm³ saturados e submetidos à tensão de -10 kPa, para obtenção do volume de poros de r eq. > 15 µm r eq. < 15 &#956;m). Os resultados permitiram concluir que o efeito da exploração agrícola sobre a porosidade é evidenciado principalmente no plantio direto nos dois solos estudados. O LVdf apresentou porosidade superior à de LVef, qualquer que seja o manejo considerado; no LVdf, somente os poros de raio equivalente > 15 &#956;m foram alterados pela exploração agrícola; e no LVef, além dos macroporos, também os poros de raio equivalente < 15 &#956;m foram afetados pelo manejo