Biochar-Fertilizer Blends-a Valuable Soil Amendment for Asparagus Cultivation?

A short-term field trial was carried out with the purpose to examine the impact of 2 different biochar fertilizer blends (BFB) on soil fertility and crop yield for a crop with a high revenue per hectare. The biochar field trial with 5 different treatments was conducted in a 2-year-old asparagus plantation on postglacial sand soil on Gotland. Besides the control (C), a biochar-fertilizer blend ("Amino Terra Substrate", ATS) of hard-wood biochar, molasses, vinasse and effective microorganisms was applied close to the asparagus row root zone in low and high application volumes of 2 ton ha(-1) (ATS-L) and 4 ton ha(-1) (ATS-H) biochar dry mass. Another biochar-fertilizer blend (CP) of rejected grain/wood biochar, cattle manure and water was applied in application volumes of 1.25 t ha(-1) (CP-L) and 2.5 ton ha(-1) (CP-H) biochar dry mass. BFB addition increased the organic carbon content, total nitrogen content, ammoniacal and nitrate nitrogen content and the plant available water storage capacity (compared to the control) and decreased soil bulk density and soil pH. In the first harvest season after BFB application, the average asparagus shoot yield exceeded (fell short of) the fertilized control by + 3.2% (ATS-H), - 0.4% (CP-L), - 5.0% (ATS-L) and - 5.1% (CP-H). In the second season after BFB application, the average asparagus shoot yield exceeded the fertilized control yield by + 10.1% (CP-L), + 8.7% (ATS-H), + 6.5% (CP-H) and + 2.8% (ATS-L). It can be concluded that the application of biochar fertilizer blends had a positive impact on soil fertility monitored within the first harvest year and the asparagus yield in the second harvest year under the observed field conditions.