Revisiting plant density by environment interaction in maize across contrasting sowing dates

Abstract

Context

The definition of the agronomic optimum plant density (AOPD) in maize is a critical management practice due to seed cost and impact on final yield. Farmers often reduce plant density when planting later in the season because of the lower expected yield compared to earlier plantings. However, this practice may lead to lost yield opportunities that need to be quantified.

Objectives

Our objectives were i) to understand how farmers define maize plant density for different planting dates and, ii) to explore the yield response to plant density in early and late plantings across a range of yield environments (YE).

Methods

We explored maize on-farm records (2017–2021; n = 25,143 fields) and field experiments (n = 491 paired comparisons) across Argentina under early (ESM) and late (LSM) plantings to characterize plant density used by farmers and attainable yields at contrasting sowing dates. Then, we conducted field experiments across different YEs, where several commercial genotypes were tested at different plant densities under both ESM (n = 39 location-years) and LSM (n = 54 location-years).

Results and conclusion

The proportion of area with ESM and LSM varied across regions and YEs in Argentina. Farmers usually chose higher plant densities at ESM than LSM, but not necessarily ESM always out-yielded LSM in the study region. Maize response to plant density varied depending on the YE, with no apparent difference between sowing dates.

Implications

Although practical reasons often justify reducing plant density in later planting, farmers should base their decisions about the AOPD based on the expected YE regardless of the planting date. Accurately predicting the YE should therefore be a key priority to optimize yields and resource allocation. The expected yield in later planting seems to be currently underestimated by farmers.