Seasonal response of edaphic bioindicators using green manure in Brazilian semi-arid conditions

Abstract

-The goal of this work was to evaluate the response of edaphic macrofauna, soil microbial biomass carbon, soil basal respiration, metabolic quotient and labile carbon of fumigated soil in a Fluvic Neosol. The experimental design was in randomized blocks, with five treatments (four green manure mix and one control) and four replications, and subsequent planting of melon (Cucumis melo L.) under semi-arid conditions in Juazeiro, Bahia State, Brazil, from August 2006 to August 2007. Soil samples were collected at a depth of 0-10 cm at 6 days before, and 117; 215 and 354 days after green manure mix planting. The results indicate that none of the attributes presented a significant difference for the treatments, but changed significantly in relation to the time of sample collection. The higher levels of soil microbial biomass carbon and labile carbon of fumigated soil were measured 117 days after planting. Soil microbial biomass carbon was inversely correlated with soil basal respiration and metabolic quotient, which increased as of 215 days after planting. At 354 days after planting, the edaphic macrofauna presented the highest density, richness, diversity and uniformity. Ants and beetles were most abundant in the areas studied.Key words -Soil quality. Macrofauna edaphic. Plant biomass. Plant mixture. Caatinga forest.Resumo -O objetivo deste trabalho foi avaliar a resposta da macrofauna edáfica, carbono da biomassa microbiana, respiração do solo, quociente metabólico e carbono lábil de solo fumigado em Neossolo Flúvico. O delineamento experimental foi em locos ao acaso com cinco tratamentos (quatro combinações de coquetéis vegetais e testemunha) e quatro repetições, e subseqüente plantio de melão na região semi-árida de Juazeiro, Bahia, Brasil, entre os meses de agosto de 2006 a agosto de 2007. Foram realizadas quatro coletas de solo na profundidade de 0-10 cm aos: seis dias antes do plantio do coquetel vegetal, 117; 215 e 354 dias após plantio do coquetel vegetal. Os resultados obtidos indicam que todos os atributos não apresentaram diferença significativa para os tratamentos com coquetel vegetal, mas diferiram significativamente em função da época da coleta. Maiores teores de carbono da biomassa microbiana e carbono lábil de solo fumigado foram obtidos aos 117 dias após o plantio. Carbono da biomassa microbiana correlacionou-se inversamente à respiração do solo e ao quociente metabólico, que aumentaram a partir de 215 dias após plantio. Aos 354 dias após plantio, a macrofauna edáfica apresentou maior densidade, riqueza, diversidade e uniformidade, tendo formigas e besouros sido os animais mais abundantes.Palavras-chave -Qualidade do solo. Macrofauna edáfica. Biomassa vegetal. Coquetel vegetal. Caatinga.

Nitrogen fixation of Poaceae and Leguminoseae in a green manure experiment in the Brazilian semiarid region

“…As C4 species have higher photosynthesis potential than C3 species, they can produce more biomass than legume species (Pedroso et al, 2014). Planting these Poaceae species as sole green manure crops is not a common practice but they have been lately tested as part of mixtures of several species planted together (Snapp et al, 2005;Miyazawa et al, 2010;Pimentel et al, 2011;Feitosa et al, 2015;Mouco et al, 2015;Pereira Filho et al, 2016). These mixtures have the potential to maximize biomass production but little is known of their capacity to fix N. Perhaps the lack of information comes from the variability of fixation in the Poaceae, apparently high in some places (Montañez et al, 2009;Morais et al, 2012;Taulé et al, 2012;Baptista et al, 2014;Santos et al, 2017) but completely absent in other places (Biggs et al, 2002;Hoefsloot et al, 2005).…”

“…Green manure may counterbalance the rapid decrease in soil organic matter brought by the high rates of organic matter decomposition, which occur under conditions of high temperature and ultraviolet radiation (Parton et al, 2007;King et al, 2012) and high soil humidity (Lee et al, 2014). In spite of green manure mixtures being a growing practice in the region (Pimentel et al, 2011;Feitosa et al, 2015;Mouco et al, 2015;Pereira Filho et al, 2016), determinations of their biomass production and especially N fixation are scarce. Periodical incorporation of spontaneous vegetation is also a growing and less studied practice in the region.…”

Biological nitrogen fixation in the Brazilian Semiarid

“…O cultivo de adubos verdes (ou plantas de cobertura) é uma prática utilizada para, entre outros benefícios, adicionar nitrogênio aos sistemas (Torres et al, 2005;Paulino et al, 2009;Zotarelli et al, 2012;Carvalho et al, 2013), mas que ainda é pouco utilizada no Semiárido brasileiro (Pimentel et al, 2011;Xavier et al, 2013). As primeiras estimativas do potencial de FBN nessa região demonstram que as quantidades de N fixadas por diferentes adubos verdes podem ser maiores que as quantidades exportadas na fruticultura irrigada, como demonstrado recentemente por Dantas (2014) e Ferreira Neto (2013).…”

Biological fixation, transfer and balance of nitrogen in passion fruit (Passiflora edulis Sims) orchard intercropped with different green manure crops

“…In irrigated crops, increased soil water availability can further accelerate decomposition rates and nutrient losses (Lee et al, 2014), leading to rapid loss of the soil productive capacity. Therefore, green manuring is a practice that has been recommended for irrigated crops as an alternative to ensure the maintenance of the soil productive capacity in the region (Pimentel et al, 2011;Xavier et al, 2013;Feitosa et al, 2015;Mouco et al, 2015;Pereira Filho et al, 2016). However, information on the quantities of biomass and N that can be simbiotically fixed by different legume species that can be used as green manure in the region is extremely scarce.…”