Project Abstract

Alfalfa seed production crops have a long growing season often harvested in Late September to early October when the weather is cooler with frost and possibility of snow or other inclement weather. 

Desiccation occurs within 7 days of application to prevent pod shattering. As a result of later harvest, desiccation can be slowed and/or less affective due to cooler weather and less intense sunshine. Therefore, desiccating seed alfalfa earlier may improve desiccation efficacy and lower the risk of inclement weather interrupting harvest activities.

The goal is to evaluate the possibility of widening the desiccation window by 1-2 weeks earlier without impacting harvestability or grain quality (dockage and/or germination). Farming Smarter applied Reglone Ion and Acetic acid, both with Li700, when the alfalfa seed crop was mature. Reglone was applied (unintentionally) at 4x rate and acidic acid at 20% v/v using 160 L/acre water volume. Reglone showed greater dry down ability than Acetic acid (20%), and late Acetic acid (20%) dried the crop more than early and standard Acetic acid (20%). No differences in yield or harvestability were observed.

Image 1: General spraying picture of Custom Research Crew, June 14, 2021.

Methods

Desiccation timing was carried out by Farming Smarter approximately 1 week before crops were fully mature (early timing), at maturity (standard timing) and approximately 1 week after full maturity (late timing). Each trial was sprayed at either dawn or dusk before so the chemicals would be absorbed into the leaves of the Alfalfa before the sun could activate them or evaporate the water on the leaf surface (making them less affective). Each trial was designed with 2.5-meter by 6-meter plots, leaving a small buffer between each plot in each block. A randomized complete block design was used with 4 blocks (replications).

Each block included each herbicide treatment (Fig. 1). A water volume of 160 L/acre was sprayed with a 2 m handheld CO2 propelled sprayer. Table 1 outlines the trial activity timeline. A visual efficacy rating was conducted on a scale of 0-100%, where 0 would be healthy plants not affected by the chemical and 100 would be brown, completed dried down plants due to the chemical. Photographs of each plot were taken right before harvest. The pictures were run through the EasyLeaf program to detect green plant material, referred to as greenness, and evaluate the efficacy of the treatments. Weights were collected for each plot, dockage weighed, and a corrected yield was calculated. A linear model with ANOVA statistics, using 95% confidence, were used to assess differences between the treatments.

Treatments
	Untreated Check
	Reglone Ion Early
	Reglone Ion Mid
	Reglone Ion Late
	Acetic Acid Early
	Acetic Acid Mid
	Acetic Acid Late

Note: Reglone Ion rate ≥ 160 L/acre water volume and 5.24 L/acre (unintended 4x rate); Acetic Acid ≥ 160 L/acre water volume and 20% concentration.

Figure 1: Trial diagram for Lethbridge field, illustrating the design methods of each trial.