Gestão agronómica e ambiental de chorumes: práticas sustentáveis de aplicação ao solo

The overall objective of this project is to identify the best option for animal slurry (liquid manure) application to soil in order to

maximize nutrient availability for plants and minimize the impact on losses to air (i.e greenhouse gases (GHG), nitric oxide

(NO) and ammonia (NH3) as well as transfers of nitrate-N (NO3-), ammonium-N, phosphorus (P), faecal pathogens

(Salmonella and Escherichia coli) and hormones (steroid) to waters.

More than 14 million tonnes of farm manures are applied to agricultural soils in Portugal each year. These inputs are a valuable

source of plant available nutrients (N and P) but also represent a significant risk of environmental pollution. Indeed, such

applications to soil may lead to important transfers of P and NO3- as well as faecal pathogens (Salmonella and Escherichia coli)

and hormones (steroid) to superficial and ground waters, On the other hand, they also induce an increase of gaseous emissions

from soils.

Moreover, the Portuguese legislation includes a ‘closed-period’ for slurry application to soil in late autumn/winter. Hence, the

amount of slurry applied in the spring and summer months should increase with direct consequences on both the amount and

timing of nutrient losses to air and water.

Injection of slurry has proven to be efficient to decrease odours and NH3 emissions and has been adopted in many European

countries. However, recent studies showed that it may increase GHG emissions such as N2O and few is known about its impact

on diffuse pollution to water. Animal slurry management strategies defined to reduce one form of pollution (e.g. NH3 emissions

to air) have to take in consideration losses by other ways (e.g. NO3- to water) and prevent their worsening to avoid the so

called “Pollution Swapping”. On the other hand, pre-treatment of slurry by solid-liquid separation and acidification proved to be

efficient to decrease NH3 and GHG emissions after soil application. An application of the liquid fraction or acidified slurry rather

than untreated slurry using surface banding technique could therefore be as efficient as slurry injection.

Hence, the main question of the proposed work is: “Is animal slurry injection in soil more efficient to reduce the associated

environmental impacts and maintain the plant production level than a combined approach of slurry treatment followed by

surface banding application?”

To answer this question, we will use the following linked approach:

1. Estimate the leaching of nutrients (N and P), faecal pathogens and estrogens hormones following untreated slurry injection

or surface band application of pre-treated slurry;

2. Compare the nitrogen and phosphorous dynamics in soil as well as the plant production in soil amended by injection of

untreated slurry or by surface banding application of pre-treated slurry;

3. Compare the GHG and NH3 emissions at soil surface in soil amended by injection of untreated slurry or by surface banding

application of pre-treated slurry;

4. Evaluate the effects of the slurry application technique and slurry pre-treatment in beneficial soil microorganisms, namely

the effect on arbuscular mycorrhizal fungi and soil biological activity more directly involved in organic matter decomposition

and N2O emissions (nitrification or denitrification).

5. Evaluate the economic impact on the farm budget of the slurry management options under study.

This project will be conducted by four complementary research teams - ISA, UTAD, IPCB, and RRNW - composed of multidisciplinary

members (chemists, soil scientists, agronomists, microbiologists, air scientists).

Six master theses as well as one PhD thesis of one junior member of the research team will be prepared during this project

and the most relevant results will be published in refereed journals and presented at international meetings. Transfer of

knowledge to farmers, industry and decision makers will be a priority of the project and achieved by the organisation of a

national workshop and elaboration of a best management practices guide for a better slurry management. Indeed, the increase

of knowledge supplied by the proposed project is essential to improve the scientific evidence base that support proposals of

new strategies to minimise diffuse pollution to air and water. This integrated approach is fundamental to efficiently reduce

diffuse-pollution from animal manures at farm scale and help farmers to comply with national regulation (nº214/2008,

November 10th). Furthermore, it will help to scientifically justify any financial support to the agricultural activity to reduce

diffuse pollution and will also contribute to meet the national objectives of complying with existing and future protocols and

directives (e.g. Gothenburg Protocol, Kyoto Protocol, Nitrates Directive, and Water Framework Directive).