For years, soil fertility in the Pampas region was managed primarily with a focus on macronutrients such as nitrogen (N), phosphorus (P), and, to a lesser extent, sulfur (S). However, recent research highlights that micronutrient deficiencies, particularly zinc (Zn), can significantly affect crop yields, potentially undermining the productivity of extensive agricultural systems.
A survey conducted by the Balcarce Integrated Unit in Buenos Aires revealed a notable decline in available zinc levels in the soil. The analysis showed that 33% of soil samples from southern Buenos Aires had zinc concentrations below 0.80 parts per million (ppm) — a threshold that could restrict wheat and barley yields. This represents a decline compared with 2011 data, when most soil samples in the region showed medium to high zinc level, according to a press release.
“Today zinc begins to show signs of deficiency in soils where historically it did not represent a limitation. The current scenario forces us to rethink diagnostic and management strategies to avoid economic and nutritional losses in crops,” said Hernán Sainz Rozas, a soil fertility specialist at INTA Balcarce.
The impact of zinc deficiency is tangible: when soils are low in zinc, wheat and barley yields can drop by 5% to 15% if crops are not fertilized. “For example, a soil with 0.75 ppm of Zn targeting 7,000 kilos per hectare could lose up to 840 kilos per hectare, a loss far greater than the cost of fertilization, which ranges between $18 and $20 per hectare,” explained Sainz Rozas.
Experts at INTA recommend preventive soil testing to identify potential deficiencies and guide fertilization strategies. According to Pablo Barbieri, specialist at INTA Balcarce, “the most reliable approach is measuring extractable zinc in samples taken 20 centimeters deep, preferably before seeding. Due to zinc’s high spatial variability, it is advisable to collect 25–35 subsamples per field using a stainless-steel sampler to prevent contamination.”
Zinc can be applied in multiple ways: solid mixtures, compound fertilizers, liquid fertilizers, seed treatments, or foliar sprays. In wheat, the crop typically extracts 200–320 grams of zinc per hectare, which can be replenished with 0.5–1 kilo of zinc per hectare.
An increasingly popular approach is the combined application of zinc and phosphorus, either through solid compound fertilizers or by coating phosphate fertilizers with liquid zinc formulations in the form of oxides or organic compounds.
“This improves the distribution of micronutrients in the soil and allows more efficient absorption by the crop,” Barbieri explained.
The low mobility of zinc in the soil profile makes replacement a strategic investment. “The goal should be to raise the levels to 1.3 ppm to avoid future restrictions. Fertilizing not only replenishes what is exported but also improves the nutritional capital of the soil in the long term,” Barbieri said.
Nahuel Reussi Calvo, a researcher at Conicet and the National University of Mar del Plata, also underlines the importance of zinc in key physiological processes such as photosynthesis, protein and sugar synthesis and auxin metabolism. “Its deficiency not only affects the growth of the crop but also reduces the efficiency in the use of nitrogen and phosphorus, essential nutrients to sustain high yields,” he explained.
The INTA Balcarce soil laboratory also provides worrying data: approximately 66% of the pampas soils today have medium to low levels of zinc, a problem already known in the north of the region, but which is now clearly manifested in the south of Buenos Aires. “Investing in intelligent diagnosis and replacement can avoid significant losses and enhance the soils of the south of Buenos Aires, a key region for wheat and barley production in Argentina,” concluded Sainz Rozas.
