This Rogations Day scene from the Benedictine monastery of Our Lady of Guadalupe is related to the fulfillment of this week's Ember Days.
The week following the Exhaltation of the Holy Cross (September 14), features the so-called "Ember Days" of September (the English word "ember" being a permutation of the Latin title Quattuor Temporum Septembris).
This special week of September on the liturgical calendar is one of the four seasonal weeks (thus, Quattuor Temporali, or Four Seasons) that have Ember Days which are related to the harvest of the fruits of the earth, which through fasting and penance we pray will be bountiful. This is also why it was customary for ordinations to holy orders (particularly the priesthood) to be held on these days, for the clergy are the harvesters of souls in the Lord's vineyard.
It is apt then to feature this Benedictine image from Rogations Week (though observed in April), during which the newly-planted crops are blessed, the fruits of which we now expectedly plan to reap. Of course, the spiritual allusion to this natural event is the sanctification (through supernatural growth) of souls and their salvation (and thus heavenly harvest).
These words of Dom Columba Marmion (Benedictine abbot at Maresous; 1858-1923) might shed further light on the spiritual lesson to be gleaned from the image:
Jesus Himself has willed to conform by a comparison our faith in His sanctifying influence: "I am the vine," He said, "you are the branches" (Jn 15:5). The branches have life, but they do not themselves provide the sap which nourishes them. They are constantly drawing their vitality from the sap which comes from the parent stem. Coming itself from another source, it is this sap which gives them life.
And so it is for the members of Christ: their good actions, their practice of the virtues, their spiritual progress, their sanctity, belong to them certainly; but it is the sap of grace coming from Christ which produces these wonders in them: "As the branch cannot bear fruit of itself, unless it abide in the vine, so neither can you unless you abide in Me" (Jn 15:4). Christ the Ideal of the Priest