Can Dairy Slurry Application to Stubble, without Incorporation into the Soil, Be Sustainable?

In many countries, livestock slurry must be injected or incorporated into the soil to reduce nitrogen losses. However, when the injection is not feasible, farmers adopting conservation practices discard the use of slurry as fertilizer. New approaches related to slurry treatment or application management can stimulate the use of slurry in conservation agriculture (CA). This study aimed to evaluate the agronomic effects of some new management strategies to use dairy slurry for fertilization of ryegrass grown on stubble-covered soil, using as reference standard practices (slurry injection and mineral fertilizer application). The following treatments were considered: (i) bare soil: control (CB), mineral fertilizer (MB), injection (IN); (ii) stubble: control (CS), acidified dairy slurry (ADS), raw dairy slurry (RDS), irrigation following RDS (IR), mineral fertilizer (MS), RDS placed under the stubble (US), raw slurry applied 16 days after sowing (RDS T16). Effects on ryegrass yield, apparent nutrient recovery (ANR) and soil chemical properties were assessed. ADS reached 94% equivalence to MS and performed similarly to IN for productivity, ANR and soil parameters showing to be a sustainable alternative to replace mineral nitrogen and a potential solution to enable dairy slurry application in CA without injection or incorporation into the soil.

Dataset on ammonia, nitrous oxide, methane, and carbon dioxide fluxes from two soils fertilized amended with treated and non-treated cattle slurry.

The current data article presents a set of fluxes of ammonia (NH3), nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2) measured from two different soils under a Mediterranean double-cropping system (oat in autumn/winter followed by maize in spring/summer). The two soils were fertilized using four different treatments: (i) Injection of raw cattle slurry (100 mm depth), (ii) application of raw cattle slurry followed by soil incorporation (20 mm depth), (iii) band application of acidified (pH=5.5) cattle slurry followed by soil incorporation (20 mm depth), and (iv) band application of acidified (pH=5.5) cattle slurry without soil incorporation. A non-amended soil was also considered as control treatment. The data presented here were obtained over a three years experiment between 2012 and 2015. Fluxes were measured in a period between slurry applications to soil (before plant seeding) till crop harvest. The data presented here are supporting the research article "Band application of acidified slurry as an alternative to slurry injection in a Mediterranean double-cropping system: Agronomic effect and gaseous emissions" (Fangueiro et al., 2018).

Reuse of treated wastewater and sewage sludge for fertilization and irrigation.

The objective of the present work was to assess the short-term potential of treated wastewater and sewage sludge for ornamental lawn fertilization and irrigation. A field experiment was performed and the following treatments were considered: sewage sludge application + irrigation with public water; sewage sludge application + irrigation with treated wastewater; irrigation with public water; irrigation with treated wastewater (TW). Irrigation with treated wastewater showed a positive effect on lawn installation through higher growth of grass (1,667 cm) and higher dry matter yield (18,147 g m(-2)). These results represent a significant increase in the grass yield compared with public water irrigation. The grass height (2,606 cm) and dry matter yield (23,177 g m(-2)) increased even more, when sewage sludge produced in the wastewater treatment plant (WWTP) was applied to soil, which proves once more its benefits as an organic fertilizer. At the end of the experiment, an increase of some soil parameters (pH, electrical conductivity, organic matter, Ca2+, Na+, K+, Mg2+ and NH4+) was observed, indicating that treated wastewater irrigation can cause a soil sodization. This short-term study indicated that use of treated wastewater and sewage sludge for ornamental lawn fertilization and irrigation is an environmentally sustainable option for re-use of the WWTP by-products.

Treatment by acidification followed by solid-liquid separation affects slurry and slurry fractions composition and their potential of N mineralization.

The aim of the present work was to assess the effect of treatments by acidification, solid-liquid separation or acidification followed by solid-liquid separation on the physical and chemical composition of pig slurry (S) and pig slurry fractions (non acidified and acidified solid (SF and ASF) and liquid (LF and ALF) fractions), as well as on the potential of N mineralization of these pig slurry derived materials. Acidification strongly decrease the inorganic carbon content of S, SF and LF and it also affects the distribution of P, Ca and Mg between the solid and liquid fraction leading to an ALF more equilibrated than LF in terms of nutrients. Acidification increases the potential of organic N mineralization in SF and decreases the potential of N immobilization in S and LF. It can be concluded that the proposed treatment generates valuable slurry fractions with distinct characteristics and potential of N mineralization that may be incorporated to soil at different periods after sowing to comply with plant nutrient requirements.

Fertilization of Pinus pinea L. seedlings with a sewage sludge-based compost.

Two experiments were conducted to evaluate the effect of a sewage sludge-based compost (SSC) on the growth and mineral composition of containerized Pinus pinea L. seedlings. In the first experiment, five different substrates were tested: four binary mixtures of SSC and peat (100% SSC, 75% SSC, 50% SSC and 25% SSC, by volume) without fertilization, and a control substrate (peat-based substrate + fertilizer). Seedlings growing in the 100% SSC substrate showed the lowest growth, a consequence of both the low water availability and the high electrical conductivity that made SSC unsuitable to be the only component of a growing-media for pine ;seedlings'. The 50% SSC substrate presented physical and chemical properties similar to the control substrate and near the acceptable range for a growing-media. Moreover, no significant differences were found between growth of seedlings from treatment 50% SSC (without mineral fertilization) and seedlings from control treatment (with mineral fertilization). In the second experiment, a fertilization assay was performed with two substrates selected from the first experiment (50% SSC and control). The two substrates were fertilized with three levels of a macronutrient fertilizer (0.5, 1.0 and 2.0 g L( -1)) and two levels of a micronutrient fertilizer (0 and 0.4 g L(-1) of fertilizer containing only micronutrients). Results obtained suggest that replacing 50% (by volume) of peat-based substrate by the sewage sludge-based compost allowed: maintenance of the commercial value of seedlings; reduction of the amount of peat used in the substrate; a need for only half the amount of macronutrient fertilizer applied in the basal fertilization; and omission of micronutrient fertilization.