INTA San Luis's Rural Extension Agency and the provincial Ministry of Productive Development brought together more than 30 agronomy professionals and students from the National University of San Luis. The workshop focused on raising maize output in Argentina's Central Semiarid Region through fertilizer decisions that reflect soil, available water and each season's attainable yield.
The starting point was to treat fertility as a physical, chemical and biological condition built over years. Central San Luis has variable water supply, sandy textures that struggle to retain organic matter and nutrient removal that often exceeds replacement. That negative balance can push soils below critical levels and constrain yield even when other production factors are favourable.
Specialists Jorge Mercau and Juan Cruz Colazo argued that phosphorus and zinc require diagnosis, regional thresholds and a long-term strategy. Replacement, maintenance and reasonable nutrient drawdown should be selected with soil tests and field history, not one dose for an entire area. INTA trial networks help calibrate recommendations for environments that respond differently.
Nitrogen demands the same precision because availability changes across sites and seasons. The workshop reviewed organic-matter mineralization, crop uptake, microbial immobilization and losses through volatilization, leaching or denitrification. Measuring mineral nitrogen before sowing, down to two metres in the profile, helps estimate real supply and avoid both deficiency and applications with no economic return.
Application method also changes efficiency. Urea left on the surface can lose a substantial share as ammonia, whereas incorporation or properly selected inhibitors can reduce that pathway. In the regional experience presented, deep drainage of fertilizer nitrogen would be highly unlikely; separating dominant risks from assumed ones directs investment towards improvements supported by evidence.
Colazo proposed turning manure, biogas digestate, agro-industrial effluent and some mining residues into resources for soils low in carbon and phosphorus. Results from San Luis production systems showed gains in yield, nutrient availability and organic matter, but use requires material testing, defined rates, soil monitoring and protection of surface and groundwater from contaminants or excess loading.
Adaptive fertilization combines stored moisture, initial nitrogen and attainable yield to decide field by field and year by year. Success should be measured through output, farm margins, nutrient balances, soil carbon, water-use efficiency and the absence of harm to water quality. With monitoring and technical rules, maize can support farming, intensive livestock and industry without turning higher yield into cumulative degradation.
