Conservation Agriculture Research Updates - April 2026

This paper from New Zealand looked at various tillage options with and without irrigation on SOC, fungal biomass and their relation to to soil aggregate sizes in a 14-year experiment. They hypothesized that long-term irrigation and intensive tillage would negatively affect soil aggregation. The experiment was started in 2003 and data taken in 2017. Two tillage treatments were intensive tillage (IT) to 20-25cm compared with no-till (direct drill - DD) and irrigation was sprinkler and none (rainfed). Soil samples (0-5 cm layer) were analyzed for pore size distribution, specific surface area and microbial biomass. Sieving was also used to separate macro- (LM) and micro-aggregates (SM), particle sized silt + clay and fine particles. Both DD and rainfed management increased total SOC content of the bulk soil. The LM and its SOC increased in DD compared to IT. A higher fungal:bacteria (F:B) ratio was generally accompanied by a greater LM fraction and mean weight aggregate diameter, highlighting the importance of fungi in the formation of LM. They concluded that detrimental effects on soil aggregation by tillage and irrigation was not conclusive and a longer study period is needed to confirm.

This study assessed the relationships between soil health and cropping system performance for three maize-based cropping systems in New Caledonia. There were two CA systems compared a conventional tillage system: direct seeding into dead mulch (CA-DM) and into a stylo living mulch (CA-LM). Soil health was evaluated using Biofunctool®, a set of ten in-field tools that assess soil carbon transformation, structure maintenance and nutrient cycling functions. Weeds, maize growth and yield components were monitored using a Structual Equation model (SEM). Soil structure maintenance and nutrient cycling functions were higher under CA-DM and CA-LM than under CT, and carbon transformation function was higher under CA-DM than under CT and CA-LM. Overall, the soil health index (SHI) was 1.3-fold higher under CA systems than under CT.