Fertigation of Maize with Digestate Using Drip Irrigation and Pivot Systems

Abstract

Digestate is a nutrient-rich fertilizer and appropriate techniques are required for its application during the maize season to reduce losses and increase the nitrogen use efficiency (NUE). The performance of two different fertigation techniques (drip irrigation and pivot) were assessed using the digestate liquid fraction. A two-year field test was carried out at two different sites in Lombardy, northern Italy. At each site, fertigation with pivot (P-F, site 1) or drip (D-F, site 2) systems was compared to reference fields where the same irrigation techniques without addition of digestate were used. During the two seasons, the performance of the fertigation systems, amount of fertilizers used, soil nitrogen content, yields, and nitrogen content of the harvested plants were monitored. The digestate application averaged 5 m3/ha per fertigation event with P-F and 4.9 m3/ha with D-F corresponding, respectively, to 28 and 23 kg N/ha. Both irrigation systems were suitable for fertigation provided that the digestate was adequately filtrated. Our results suggest that fertigation with digestate, if properly managed, can be applied during the growing season up to the full amount of nitrogen required by the crop.

Reducing Topdressing N Fertilization with Variable Rates Does Not Reduce Maize Yield

“…In our study, the S-index, Topdressing N, and yield in 2017 and 2018 showed different average values between the two years. This was observed throughout the region [50] because of severe biotic stress due to European corn borer (Ostrinia nubilalis) and fungal diseases causing a declining rate of crop production. In general, FR often results in a maize grain yield increase in response to increasing N rates if no water stress occurs [26].…”

Evaluation of ammonia emissions from filtration of digestate used for fertigation

“…The available techniques to reduce agricultural NH3 emissions include inter alia covering manure and slurry storage facilities, cooling storage facilities and/or contents, acidifying slurry, stripping NH3, fractioning fertilization during crop growth, and fertigation using slurry or digestate (Rotz et al, 2014;European Commission, 2017). Fertigation is a valid alternative to other fertilization practices, because it can minimize nitrogen loss, while facilitating the utilization of animal (and crop) wastes, thereby contributing to circularity within a farming system (European Commission, 2017;Finzi et al, 2019;Guido et al, 2020a).…”

“…The separated digestate is an excellent fertilizer, because the retained nitrogen is in ammoniacal form, which is readily used by plants (Guilayn et al, 2019). However, for the same reason, the potential for NH3 emissions to occur from digestate is high (Guido et al, 2020a). To minimize these emissions, care and attention must be exerted when utilizing this product.…”

“…Fertigation using digestate via drip irrigation or sprinkler irrigation (such as driplines or pivot systems) can be a suitable technique to overcome these problems. Fertigation allows the total dose of nitrogen to be fractionated throughout the growing season, thereby limiting nitrogen emissions both in the soil and in the air (Hanson et al, 2006;Guido et al, 2020a). However, when the liquid fraction of digestate is used in fertigation, additional filtration (after a screw press) is required to remove solids that are larger than the nozzle holes in the irrigation system.…”

“…However, when the liquid fraction of digestate is used in fertigation, additional filtration (after a screw press) is required to remove solids that are larger than the nozzle holes in the irrigation system. Typically, advanced filtration is achieved using mechanical separation equipment such as vibrating screens or micro-filters that have screen openings of 50-500 microns (Guilayn et al, 2019;Guido et al, 2020a).…”