Nitrogen fertilization enhances soil quality in the short-term in irrigated intensified maize systems

Aim of study: This study had a double objective that consisted of: (i) assessing the effects of N fertilisation on soil quality under different cropping systems (monocropping vs. double-annual cropping systems) under irrigated maize conditions; and (ii) identifying soil parameters related to soil quality that respond quickly to short-term management changes in Mediterranean irrigated maize systems. Area of study: Zaragoza province, Spain Material and methods: The field experiment involved a strip plot design with three growing systems – maize monoculture (MM), pea-maize (PM), and barley-maize (BM)– and three fertilisation levels: unfertilised (0N), medium nitrogen (MN), and high nitrogen (HN). After two years, soil samples were collected at two depths (0-10 cm and 10-30 cm). Soil parameters measured related to soil quality were total soil organic carbon (SOC), water-stable macro aggregates (WSM), macroaggregate C concentration (Macro-C), particulate organic matter carbon (POM-C), permanganate-oxidisable organic carbon (POxC), soil microbial biomass carbon (MBC), and enzyme activity: dehydrogenase (Dhns) and ß-glucosidase (Gds). Main results: Our research showed that in intensified systems, the highest fertilisation rate improved soil parameters in the topsoil by enhancing all the soil parameters tested except for the dehydrogenise enzyme activity. In contrast, in the monoculture, the highest fertilisation rate only increased SOC and Macro-C. Fertilisation had a higher impact on soil quality in the BM system compared to the PM system, probably related to greater quantities of crop residues in the BM system under a high fertilisation rate. Research highlights: Nitrogen fertilisation improves soil parameters related to soil quality in intensified systems and the magnitude of the fertilisation impact may depend on crop species and residues. The impact of N fertilisation on soil quality can be detected in the short term when testing early indicators of soil quality.