A review of 25 studies found that variable-rate nitrogen management reduced inputs, improved nitrogen efficiency and raised profits.
Researchers reviewed 25 studies containing 235 paired comparisons of in-season optical sensor-based variable-rate nitrogen application and fixed-rate management in maize. They assessed nitrogen inputs, grain yield, nitrogen-use efficiency and profit, along with the effects of market prices, application timing and management choices.
Variable-rate application performed best when little or no nitrogen had been applied before planting. The economic results also depended on the application algorithm and when nitrogen was applied during the growing season, with early- to mid-season timing identified as important.
What the sensors changed
Compared with the uniform-rate treatments in the included studies, variable-rate nitrogen application reduced total nitrogen use by 18%, increased partial factor productivity of nitrogen—a measure of grain produced per unit of nitrogen—by 22%, and increased partial profit by 6% without changing grain yield. Profitability remained significant across all six market scenarios examined and increased as the nitrogen-to-maize price ratio rose.
The largest agronomic benefits occurred when pre-plant nitrogen was absent or limited to 12 kilograms per hectare or less. Economic results were shaped mainly by the application algorithm and timing. Profit and nitrogen-use efficiency both improved in 57% of the paired comparisons.
Why lower inputs matter
The findings suggest that maize can receive less nitrogen while maintaining yield when applications are adjusted to crop conditions during the season. That combination could improve the economic return on nitrogen and reduce unnecessary fertilizer use in the management settings represented by the studies.
The results also point to conditions that matter for success: applying little nitrogen before planting, choosing an appropriate decision-making algorithm and applying nitrogen early to mid-season. These factors mean that variable-rate management is not a single approach with identical results in every field.
Evidence and caveats
This was a systematic review and meta-analysis of 25 studies and 235 paired comparisons, rather than a new field experiment. The researchers combined results using statistical models and examined how management and market conditions modified the outcomes.
The conclusions apply to the studies included in the review and their reported comparisons with uniform-rate treatments. Results varied with pre-plant nitrogen strategy, algorithm design and application timing, so the reported averages do not represent the outcome of every variable-rate program or maize-growing setting.
// Source
Precision Agriculture · 2026 · DOI: 10.1007/s11119-026-10447-1
Authors: Amrinder Jakhar, Gonzalo J. Scarpin, Lorena N. Lacerda, Brenda V. Ortiz, Miguel L. Cabrera, George Vellidis, Leonardo M. Bastos
Institutions: University of Georgia, National Agricultural Technology Institute, Auburn University, Instituto Nacional de Tecnologia, Instituto Nacional de Investigaciones Agropecuarias
