Relationship between the leaf area index and wheat grain yield in commercial fields in the Yaqui valley, Sonora, Mexico

The leaf area index (LAI) is a key plant parameter for modeling the mass exchange and energy between the biosphere and the atmosphere, which allows the study of development, growth, and agronomic yield of crops. The critical period for diminishing the wheat leaf area occurs 30 days around flowering and may cause a reduction in the real number of spikes/m2, spikelets/spike, number of grains/m2, and grain weight. The objective was to determine the relationship between the LAI and grain yield during the phenological development, in different sowing dates in thirteen commercial wheat fields, sown with durum cultivar CIRNO C2008, in the Yaqui Valley, Sonora, Mexico, during the fall-winter 2021-2022 crop season. Field surveys were carried out to monitor crop development, and to take readings of the LAI using a linear ceptometer; also, four 1 m2 samples were harvested from each field in order to count the number of spikes and to calculate grain yield. The LAI was not constant in ten of the selected fields according to the development of wheat; however, there were three fields (B-703, B-725, and B-1512) where there was a positive correlation between the LAI and grain yield which reached more than 8.2 t ha-1. The highest expression of the LAI occurred during ½ grain formation. The average grain yield of the monitored fields was 7.22 t ha-1, being December 14, 2021, the sowing date with the highest yield (8.43 t ha-1), while the highest number of spikes/m2 occurred on the December 11 sowing date with 428. Measurement of the LAI indirectly, could be considered an appropriate method, but environmental conditions and agronomic management by producers must be taken into account in order to make yield estimates.