<b>Soil properties and cowpea yield after six years of consecutive amendment of composted tannery sludge

Abstract

ABSTRACT. This study evaluated soil properties and cowpea yield after six years of consecutive amendment of composted tannery sludge. The compost was applied annually at 0, 2.5, 5, 10, and 20 Mg ha -1 and at the end of the sixth year, the chemical and physical properties of the soil were evaluated using a randomized block design. The Cr, P, K, Ca, Na and organic C contents and the pH and cation exchange capacity increased linearly after six years of compost amendment. The soil bulk density decreased linearly while the aggregate stability index increased after compost amendment. As a consequence of the changes in the chemical and physical properties of the soil, cowpea yield showed a quadratic response to the tannery rates, with an estimated maximum cowpea yield at 8.3 Mg ha -1 . In conclusion, the soil chemical and physical properties improved after six years of composted tannery sludge amendment. However, the soil pH and the Cr and Na contents increased with composted tannery sludge amendment, which influenced the cowpea yield and resulted in a quadratic response to the compost.Keywords: waste management, soil fertility, soil quality.Propriedades do solo e produtividade do feijão-caupi após seis anos de aplicações consecutivas de lodo de curtume compostado RESUMO. Este estudo avaliou as propriedades do solo e a produtividade do feijão-caupi após seis anos de aplicações consecutivas de lodo de curtume compostado. Anualmente, o composto foi aplicado a 0, 2,5, 5, 10 e 20 Mg ha -1 e no sexto ano as propriedades químicas e físicas do solo e a produtividade do feijão-caupi foram avaliadas em experimento de blocos casualizados. Cr, P, K, C orgânico, pH, Ca, Na, e a capacidade de troca de cátions aumentaram linearmente após seis anos de aplicação do composto. A densidade do solo diminuiu linearmente enquanto a estabilidade de agregados aumentou após a aplicação do composto. Em consequência das mudanças nas propriedades químicas e físicas do solo, a produtividade do feijão-caupi apresentou resposta quadrática às doses de lodo de curtume compostado com máxima produtividade estimada encontrada na dose de 8,3 Mg ha -1 . Em conclusão, as propriedades químicas e físicas do solo melhoraram após seis anos de aplicação do lodo de curtume compostado. Entretanto, o pH do solo, bem como os teores de Cr e Na aumentaram com aplicação do lodo de curtume compostado e estes parâmetros influenciaram a produtividade do feijão-caupi que apresentou resposta quadrática.Palavras-chave: manejo de resíduos, fertilidade do solo, qualidade do solo.

Physiological and biochemical responses of selected cowpea (Vigna unguiculata (L.) Walp.) accessions to iron toxicity

“…The low osmotic potential has been shown to extend the time needed for imbibition as well as delaying the onset of germination. Results obtained were similar to those of Olasoji et al (2013) and Araujo et al (2016) who also observed differential response for the rate of water of imbibition for 2019) who observed a reduction in soluble sugar content in rice exposed to iron toxicity. Development of oxidative stress in plants exposed to heavy metals is largely ascribed to the heavy metalinduced imbalance between the generations of toxic oxygen radicals and their scavenging through the antioxidative defence mechanisms.…”

Chemical variables influencing microbial properties in composted tannery sludge-treated soil

“…According to the analysis of similarity matrices BIOENV, Ca was the single variable that initially influenced the microbial properties in the soils amended with CTS. In this long-term experiment, the results showed an increase in Ca content in soil after CTS amendment (Araújo et al 2016) and it influenced negatively the soil microbial biomass due to the lower bioavailability of organic matter to soil microbial processes promoted by the high Ca content (Rosenberg et al 2003). Therefore, Ca acts indirectly on soil microorganisms inhibiting their access to the bioavailable fraction of the organic matter via chemical binding with its labile structures (Whittinghill and Hobbie 2012).…”

“…Cr was also the single variable that significantly influenced the soil microbial biomass because of its strong accumulation from 2010 to 2014 (Araújo et al 2016). It indicates that the application of CTS increased Cr bioavailability and adversely affected the soil microbial biomass, respiration, and enzymes activity.…”

“…Therefore, studies focusing on TS composting were performed aiming to evaluate the amendment of composted tannery sludge (CTS) on soil microbial properties in long term (Santos et al 2011;Gonçalves et al 2014;Silva et al 2014;Araújo et al 2015). These studies have shown that the annual application of CTS changed the soil microbial biomass, respiration, and enzymes activity (Santos et al 2011;Gonçalves et al 2014;Silva et al 2014;Araújo et al 2015), and increased the soil organic C, pH, salinity, and Cr content (Araújo et al 2013;Araújo et al 2016). Similarly, Singh and Agrawal (2010) reported that the amendment of sewage sludge also increased the values of soil organic C, pH, electric conductivity, and metals in soil.…”

Changes on microbial C and enzyme activities in soil with amendment of composted tannery sludge after 9 years

“…The use of municipal and industrial wastes in agricultural soils has increased in the world, since these wastes are accumulating in the environment (Boechat et al 2017). Among them, tannery sludge presents organic and inorganic substances, such as salts and carbonates, but mainly chromium (Cr) (Araújo et al 2016) and, thus, the amendment this waste should be monitored over time to prevent soil pollution. However, some alternative methods for treating the tannery sludge, before its application in soil, could be applied, such as composting (Sousa et al 2018), although this process does not degrade metals.…”