Several solutions are today proposed to farmers to minimize ammonia (NH 3 ) emissions during storage. In the present study, special attention was given to slurry acidification and slurry crust enhancement and our objective was to assess the effect of slurry bio-acidification using sugar and cheese whey as an alternative to sulphuric acid, and the potential of rice bran as crust enhancer on NH 3 and greenhouse gases emissions during storage. Both the cheese whey and the rice bran are materials, available in large amounts, with low commercial value in some EU regions as Portugal and its use, at farm scale, will be a win-win situation. Sugar is also a good alternative to acid attending its relatively low value. A laboratory experiment was performed for 2 months with five treatments: non-treated cattle slurry (CTRL), slurry treated with sulphuric acid (ACID), slurry treated with sugar (SUGAR), slurry treated with cheese whey (WHEY) and rice bran applied on the slurry surface (RICE). The SUGAR treatment led to a reduction of NH 3 emissions by 45% relative to CTRL while WHEY and RICE resulted in a reduction of 68% and 25%, respectively. Nevertheless, this effect of SUGAR and WHEY was shorter than in ACID, since NH 3 emissions started to be observed in those 2 treatments after 31 and 35 days of storage, respectively. Nitrous oxide emissions remained close to zero in ACID and SUGAR. RICE led to the highest emissions of carbon dioxide (CO 2 ) releasing almost 5% of carbon present in the initial mixture (slurry þ rice bran) and presented the highest methane emissions. The ACID and SUGAR led to a significant decrease of the total greenhouse gas (GHG) emissions. Our results indicate that bio-acidification using a source of sugar could be a good alternative to H 2 SO 4 to reduce simultaneously NH 3 and GHG emissions during storage.

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Producing manure-based fertilizers (MBFs) with specific nutrient ratios is a solution to overpassing the imbalance of nitrogen and phosphorus in manures, and a way to recycle manure’s nutrients, promoting sustainable agricultural practices. Several MBFs with different tailored N:P ratios (0.5:1, 1:1 and 2:1) were produced to determine their agronomic value in a pot experiment with oat (0.5:1 ratio: cattle manure with pig slurry (CaM+PiS), cattle manure with poultry manure (CaM+PoM) and poultry manure with superphosphate (PoM+SP); 1:1 ratio: poultry manure with cattle slurry (PoM+CaS) and poultry manure with pig slurry (PoM+PiS); 2:1 ratio: cattle slurry with the liquid fraction of cattle slurry (CaS+CaS-LIQ), pig slurry with the liquid fraction of pig slurry (PiS+PiS-LIQ) and poultry manure with urea (PoM+U)). The performance of these MBFs was compared with conventional mineral fertilizers (MFs) in sandy soils (Haplic Arenosols) with different nutrient requirements. Oat fertilized with PoM+SP (0.5:1) and PoM+PiS (1:1) led to yields similar to those obtained with the use of MFs (6.3 and 7.2 mg DM, respectively). The MBFs PoM+SP and PoM+PiS, as well as PiS+PiS-LIQ (2:1), were agronomically equivalent to the MFs. N uptake with those MBFs was equivalent to that obtained with the MFs. Replacing MFs with MBFs in the basal fertilization of oat was demonstrated to be a solution to turn agriculture more sustainable by recycling nutrients efficiently.

The application of manure-based fertilisers (MBFs) is considered an important practice for achieving agricultural sustainability. However, the potential losses of nutrients to the environment need to be thoroughly evaluated. This study aimed to assess nutrients’ potential leachability from a sandy soil, fertilised with MBFs produced by mixing manure from one single animal species with N- or P-mineral fertilisers, to achieve target N:P ratios (1:1, 2:1 and 0.5:1). MBFs were prepared by combining pig slurry, cattle slurry or poultry manure with N- and P-mineral fertilisers, or slurry-derived materials, obtained by solid–liquid separation. A leaching experiment was set-up in soil columns treated with MBFs, for 59 days, with seven leaching events. Poultry manure application to soil led to higher potential N leaching, while pig slurry induced higher P leaching. All 2:1 MBFs decreased P leaching, relative to the original manure, with the higher reduction (52%) being observed for pig slurry with urea. The addition of urea to poultry manure also diminished its potential for N leaching. The behaviour of P-enriched materials, pig slurry solid fraction and both 0.5:1 MBFs obtained with phosphoric acid addition showed a higher risk of P leaching, while the use of superphosphate as a P-mineral source decreased the risk of P leaching. Concluding, it is possible to use specific MBFs, enriched with N and P from mineral sources, and have lower N and P leaching potential, reducing the risks associated with manure soil application, while increasing their interest as alternative fertilisers.