Modification of soybean plant architecture through growth regulators and population variation

An important limitation to increased soybean [Glycine max (L.) Merr.] grain yield is excessive plant growth. The use of growth regulators and population adjustment is imperative for the management of soybean. This study aimed to evaluate whether lactofen, used as a growth regulator, and a reduction in plant population affected the architecture of soybean and increased its production efficiency. The study was carried out under field conditions during the 2017–2018 and 2018–2019 seasons. The experimental design was in completely randomised blocks with five treatments and five replications: T1 (control), T2 (application of 140 g a.i. ha−1 of lactofen at phenological stage V3), T3 (application of 140 g a.i. ha−1 of lactofen at phenological stage V6), T4 (plant population 20% lower than recommended) and T5 (plant population 40% lower than recommended). The plant height, the number of nodes, the number of branches, stem diameter, and the internode distance were affected by lactofen application at stage V3. Lactofen use at stage V3 also increased the coverage percentage and the number of droplets per square centimetre of phytosanitary products. The interception of solar radiation was higher with lactofen application at stage V3 and that treatment provided the highest yield. Therefore, the use of lactofen as a growth regulator improves soybean grain yield. A reduction in plant population had the greatest effect on grain number and weight. Plant density should be maintained as recommended to avoid a decrease in grain yield