A meta-analysis of physicochemical changes in the rhizosphere and bulk soil under woodlands

Monoculture for timber production has been replacing natural environments as the demand for renewable energy sources increases. The lack of nutrient compensation may increase the risk of soil depletion, thus changing soil properties. To summarize the impact of forestry activities in edaphic environments, we present a meta-analysis on the rhizosphere effects of coniferous and broadleaved trees established as monoculture and natural regeneration on soil physicochemical properties. Records of soil attributes published in peer-reviewed journals from eight countries were collected. Clay content changed only in monoculture sites, decreasing 55.51% in the rhizosphere, while silt and sand presented significant variations in both monoculture and naturally regenerated areas. Conifers affected the soil more than broadleaved trees, evidenced by higher pH reduction (-2.96% vs. -1.98%) and higher increase of Al3+ (197.43% vs. 50.68%), K+ (80.40% vs. 69.90%), CEC (24.61% vs. 17.35%), and total organic carbon (82.21% vs. 69.89%). Also, the rhizosphere affected regeneration soils more than monoculture, indicated by higher Al3+ (50.68% vs. ns) and available P (32.31% vs. ns), K+ (203.44% vs. ns), CEC (34.90% vs. 20.93), and total organic carbon (91.55% vs. 63.23%). These results indicate higher nutrient availability in naturally regenerated than monoculture sites, as higher species diversity and better plant litter quality are expected. This meta-analysis shows that coniferous and naturally regenerated trees had a higher influence on the rhizosphere and soil properties than broadleaved and monocultures. Management practices must be revisited to ensure the long-term sustainability of forestry activity, and studies in tropical zones must be intensified.

Combination of inoculation methods of Azospirilum brasilense with broadcasting of nitrogen fertilizer increases corn yield / Combinação de métodos de inoculação de Azospirillum brasiliense com adubação nitrogenada de cobertura aumenta produtividade de milho

Nitrogen (N) is the most limiting nutrient for corn production. Thereby, the goal of the paper was to evaluate inoculation methods of Azospirillum brasilense in order to partially supply N required by the crop. The experiment was carried out in Guarapuava, PR, Brasil, in 2011/2012 growing season. Randomized blocks with factorial 3 inoculation methods (seed treatment, planting furrow and non-inoculated control) x 5 doses of nitrogen (0, 75, 150, 225 and 300kg ha-1) x 8 replications was used as the experimental design. Leaf are index, foliar nitrogen content, total chlorophyll, grains per ear and yield were evaluated. There was significant interaction between inoculation methods and nitrogen fertilization to leaf area index, but not for yield. Inoculation with the diazotrophic bacteria provided yield increase of 702kg ha-1 for inoculation in seeding furrow and 432kg ha-1 for inoculation in seed treatment compared to the control, but both treatments did not differ between each other. Furthermore, total chlorophyll, grains per ear and yield were positively affected, with quadratic response, by the nitrogen fertilization in broadcasting.

O nitrogênio (N) é o nutriente que mais limita a produtividade da cultura do milho. Dessa forma, o objetivo deste trabalho foi avaliar métodos de inoculação de Azospirillum brasilense para suprir em parte o nitrogênio requerido pela cultura. O experimento foi conduzido em Guarapuava, PR, Brasil, no ano agrícola de 2011/2012. Os tratamentos foram dispostos em delineamento de blocos ao acaso, em esquema fatorial 3 métodos de inoculação (tratamento de sementes, sulco de plantio e controle não inoculado) x 5 doses de nitrogênio (0, 75, 150, 225 e 300kg ha-1), com oito repetições. As variáveis analisadas foram: índice de área foliar (IAF), teor de N foliar, clorofila total, grãos por espiga e produtividade. Houve interação significativa entre os métodos de inoculação e a adubação nitrogenada para a variável IAF, mas não para a produtividade. Concluiu-se que a inoculação com a bactéria proporcionou incremento na produtividade de 702kg ha-1 para inoculação no sulco de semeadura e de 432kg ha-1 no tratamento de sementes, comparado com o controle, mas não houve diferença significativa entre esses dois tratamentos. Além disso, o teor de clorofila total, número de grãos por espiga e produtividade foram afetados positivamente, obtendo-se resposta quadrática, com aplicação da adubação nitrogenada.

Efeito residual do nitrogênio na cultura do milho no sistema de produção integração lavoura-pecuária / Residual effect of nitrogen in the maize production in crop livestock integration

O nitrogênio (N) é um dos nutrientes exigidos em grandes quantidades pelas plantas. Sua aplicação na pastagem, em integração lavoura-pecuária, pode proporcionar alta produtividade animal no inverno e vegetal no verão. O objetivo deste trabalho foi avaliar o efeito residual da aplicação de N na pastagem, com e sem pastejo, sobre a cultura do milho. O experimento foi realizado em Guarapuava (PR) na safra 2007/08, em delineamento de blocos casualizados com parcelas subsubdivididas. A parcela principal consistiu dos tratamentos com N no inverno (N-TI = 0, 75, 150 e 225kg ha-1 de N) em pastagem de aveia branca (Avena sativa L.) e azevém (Lolium multiflorum Lam.), na subparcela com (CP) e sem pastejo (SP) de ovinos e, nas subsubparcelas N no verão (N-TV = 0; 75; 150; 225 e 300kg ha-1 de N). A semeadura do híbrido 30F53 ocorreu no dia 24/10/07. As variáveis avaliadas foram fitomassa seca da pastagem, produtividade, número de fileiras, grãos por fileira, grãos por espiga e massa de mil grãos. A fitomassa seca CP e SP teve resposta quadrática para as dose de N-TI. A produtividade de grãos, assim como o número de fileiras e grãos por espiga não foram afetados pelo pastejo. Houve resposta quadrática na produtividade de grãos em função do aumento das doses de N-TI e N-TV.

The nitrogen is an element required in large quantities by plants. Its application in the pasture, in crop-livestock integration, would provoke high animal productivity in winter and high vegetal productivity in summer. This study aimed to evaluate the residual effect of nitrogen application in the pasture, with and without grazing sheep, under maize culture. The experiment was conducted in Guarapuava (PR) in the 2007/08 season in a randomized block design with split plots. The main parcel consisted of treatments with N in winter (N-TI = 0, 75, 150 e 225kg ha-1 de N) in pasture of white oat (Avena sativa L.) and ryegrass (Lolium multiflorum Lam.), in subparcel with (CP) and without grazing (SP) sheep and, in subsubparcels N in summer (N-TV=0; 75; 150; 225 e 300kg ha-1 de N). The sowing of hybrid 30F53 occurred on 10/24/07. The variables evaluated were: pasture dry mass, productivity, numbers of rows, grains per rows, grains per spike and grain thousand mass. The dry mass plant CP and SP had quadratic response to the level of N-TI and N-TV. The productivity of grains, as well as the number of rows and grains per spike, was not affected by grazing. There was quadratic response in productivity of grains, due to the increase of nitrogen levels N-TI and N-TV.