Search

Context. Organic amendments in agricultural systems benefit the soil biota; however, their consecutive use can interfere negatively with the biota diversity and functionality. Aims. This study evaluated the biomass and microbial activity and the epiedaphic fauna response of soil with consecutive liquid cattle manure (LCM) addition (4 years) in no-tillage. Methods. The experiment was run in two Oxisol textures: sandy clay loam and clayey. The treatments were the control (un-manured) and three LCM doses: 60, 120 and 180 [m.sup.-3] [ha.sup.-1] [year.sup.-1], distributed in a completely randomised block design with four replications. Microbial biomass carbon (MBC), soil microbial respiration (SMR), and microbial quotient (qMIC) were performed in the 0-5 cm layer. The epiedaphic fauna was captured by traps and abundance and ecological indices were evaluated in spring and autumn seasons. Key results. In sandy clay loam soil, the MBC and SMR increased up to 180 [m.sup.-3] [ha.sup.-1] [year.sup.-1] in both spring and autumn, while in clayey soil, only the SMR increased up in the spring. The most representative groups of the epiedaphic fauna were Collembola, Acarine, Coleoptera, and Hymenoptera. The Collembola population was predominant in both soils and seasons. Conclusions. Consecutive annual applications of LCM in no-tillage had a greater positive impact in the soil biota in the sandy clay loam soil and in the spring season and did not negatively affect the ecological functioning of the soil biota system. Implications. Application of liquid cattle manure may be beneficial for the sustainability of the agroecosystem and as a highly available and low-cost waste, it may be an alternative for replacing chemical fertilisers. Keywords: animal manure, epiedaphic fauna, microbial biomass, microbial quotient, microbial respiration, Pielou, Shannon, Simpson, soil tillage., Introduction It is a great challenge to apply agricultural production system that promotes economic development and environmental sustainability. The intensive use of mechanisation, pesticides and mineral fertilisers, additional to the [...]

Native grassland supports extensive livestock production in the Pampas of South America, but the impact of cattle excreta on nitrous oxide ([N.sub.2]O) emissions remains unknown in this biome. The objective of this study was to determine the [N.sub.2]O emission factor (EF-[N.sub.2]O, % of N applied that is emitted as [N.sub.2]O) for urine and dung from beef cattle grazing on native grasslands. A field trial was conducted under low and moderate forage allowances (FA4 and FA12; i.e. 4 and 12 kg dry matter/100 kg live weight respectively) during the 30th year of a long-term grassland experiment on a Typic Paleudult in South Brazil. Urine and dung were applied onto separate patches, at rates equivalent to one average urination or defecation; and [N.sub.2]O fluxes were monitored with closed static chambers over 338 days. In adjacent microplots receiving the same excreta treatment, water-filled pore space, nitrate, ammonium and extractable dissolved organic carbon were monitored in the top 0.1 m of soil. Averaged across the forage allowances, daily soil [N.sub.2]O fluxes were low in the control without excreta (1.3 g N [ha.sup.-1]), but increased upon application of dung (3.8 g N [ha.sup.-1]) and urine (66 g N [ha.sup.-1]). The annual [N.sub.2]O emission and the EF-[N.sub.2]O for urine were greater under FA12 than FA4, but no difference was observed for dung. The positive relationships between [N.sub.2]0-N emissions and ammonium intensity and nitrate intensity suggest that [N.sub.2]O may have been produced concurrently by nitrification, nitrifier/denitrification and denitrification. On average, the EF-[N.sub.2]O was almost 10 times higher for urine than for dung (0.74% vs 0.08%), both much lower than the IPCC's Tier 1 default value of 2%. Our findings reinforce the need for disaggregating the EF-[N.sub.2]O for urine and dung and of revising the IPCC's Tier 1 EF-[N.sub.2]O. Additional keywords: cattle excreta, forage allowance, livestock, [N.sub.2]O, subtropical. Received 27 April 2019, accepted 29 October 2019, published online 9 December 2019, Introduction The Pampa biome extends over 750000 [km.sup.2] in Uruguay, northern Argentina and southern Brazil. In Brazil, the Pampa's native grasslands support a grazing herd of 13 million cattle (Carvalho [...]

Fluorescence spectroscopy relies on the fluorescence emitted by rigid conjugated systems and thus can be used to assess the soil organic mailer (SOM) humification. This technique is generally applied to solution samples of humic substances, and so far no information exists about its applicability to whole untreated soil samples. The laser-induced fluorescence (LIF) spectroscopy is proposed as a novel technique to assess the organic matter humification in whole soil samples. We sampled the 0- to 2.5-, 2.5- to 5-, 5- to 10-, 10- to 15-, and 15- to 20-cm layers of three Oxisols of long-term experiments located in two sites of the Brazilian Cerrado. The humification index based on LIF spectroscopy ([H.sub.LIF]) of whole soil samples showed a close correlation with the humification indexes [A.sub.4]/[A.sub.1], [I.sub.465]/[I.sub.399], and [A.sub.465] obtained after fluorescence spectroscopy analysis of the dissolved humic acids. The [H.sub.LIF] in soils under native cerrado or subjected to no-tillage increased from the top to the deepest layer, which is consistent with the deposition of labile organic mailer from plant residues on the soil surface. The soils subjected to conventional tillage, however, showed relatively constant [H.sub.LIF] along the profile, possibly because homogenization imparted by disturbance of the arable layer. Accordingly, for the two top layers, the soils under no-tillage showed a lower [H.sub.LIF] than for conventionally tilled soils. Laser-induced fluorescence spectroscopy is a promising technique to assess humification in whole soil samples, particularly in Oxisols, which due to high concentration of [Fe.sup.3+] are not feasible to electron spin resonance (ESR) and Carbon-13 nuclear magnetic resonance ([sup.13]C NMR) spectroscopy, unless previous treatment is employed.