Biogas residues in substitution for chemical fertilizers: A comparative study on a grassland in the Walloon Region

Abstract

To provide sufficient quantities of food and feed, farming systems have to overcome limiting factors such as the nutrient depletion of arable soils. Nitrogen being the main mineral element required for plant growth, has led to the extensive use of chemical fertilizers causing nitrogen pollution of the ecosystems. This field study investigates the use of biogas residues (BRs) as biofertilizers and their contribution to the mitigation of nitrate leaching in agricultural soils, while also demonstrating the polluting nature of chemical fertilizers. Nine different fertilization treatments classified in three schemes and two nitrogen doses were tested for three consecutive years on a grassland in the Walloon Region of Belgium. Residual soil mineral nitrogen, percentage contribution of treatments in residual nitrate and agronomic performance were assessed for each fertilization treatment. The results obtained showed significant differences on treatment and scheme level regarding nitrate accumulation in the soil, with chemical fertilizers posing the highest nitrate leaching risk. BRs did not cause nitrate accumulation in the soil, and were N rate and rainfall independent, while the chemical treatments indicated a cumulative tendency under high N rate and low precipitation. Forage yield did not demonstrate statistical differences on treatment and scheme level but varied with changing precipitation, while the maximum application rate suggested a

Assessing the Effects of Digestates and Combinations of Digestates and Fertilizer on Yield and Nutrient Use of Brassica juncea (Kai Choy)

“…The LBD50 treatments were just below this threshold and still produced slightly, albeit insignificantly, more biomass than did the fertilized control treatment. This is similar to findings from Tsachidou et al [23], where substituting chemical fertilizers with digestate up to 65% showed no reduction in biomass and Wang et al [20], where substituting mineral fertilizer with poultry digestate up to 50% produced beneficial results. However, Maunuksela et al [21] found increased or similar growth of barley with digestate addition, but an inhibition of growth with Chinese cabbage.…”

“…However, two studies have found that replacing some fertilizer with digestate can produce similar or greater plant growth than fertilizer alone [20,22]. There is a lack of information on how digestates affect plant growth and nutrient status when combined with fertilizers, and the only information available on the combination is either in grassland or hydroponic systems, both quite different from annual vegetable systems [20,23].…”

The Analysis of the Economic Effects on the Greening and Recovery of the Sludge Waste Resulting from the Biogas Production Activity

“…As a result of the composting treatment, the viscosity and odors of the residue are reduced, as well as its phytotoxicity [80][81][82]. According to studies, the sludge, that can be used in agriculture as liquids (this type of sludge being the best for agriculture), semi-dry or dry, has superior qualities compared to chemical fertilizers and are superior to aerated fermented manure [48,[82][83][84][85][86][87]. On the other hand, the sludge from biogas plants has a pesticidal effect, but according to several authors [87][88][89][90], no harmful effects common for chemical products, bringing more microorganisms (bacteria and fungi) into the soil and not endangering human health when they are recycled to farmland [45].…”

Nitrogen fertilising products based on manure and organic residues. Supporting literature of the SYSTEMIC factsheets

“…Also, in Belgium, Tsachidou and colleagues (Tsachidou et al 2019) carried out a similar experiment on a grassland soil used for grazing. In this case, the concentration of nitrate at 90 cm depth for the parcels fertilized with digestate liquid fraction was always lower than that found at the same depth for the parcels fertilized with ammonium nitrate.…”