Written by Dan Wiersma, Alfalfa Business Manager
Every alfalfa forage harvest operation requires multiple trips over a field with tractors, mergers, choppers or balers, and wagons or trucks. This normal harvest-time traffic can injure plant crowns, crush newly emerged alfalfa buds and shoots, and easily cause soil compaction. Physical plant injury creates an opportunity for disease organisms to enter alfalfa crowns and roots. Damaged crowns and shoots can result in a reduction of root and crown carbohydrates, poor plant vigor, and shorter stand life. Soil compaction in the traffic lanes where harvesting equipment is driven reduces water infiltration rates and limits the amount of water available to the root system resulting in less than optimum plant growth. Compaction of soil layers can occur under a wide variety of soil types and field soil conditions with the most severe damage in saturated soils.
Many factors influence the severity of plant damage, yield loss, or stand reduction which occur with harvest-time wheel traffic activities. Understanding these alfalfa-damaging factors helps in developing management strategies to reduce the impact of wheel traffic on alfalfa.
Several universities have conducted alfalfa research trials to help understand the impact of wheel traffic on plant health, forage yield, and stand persistence.
A Univ. of Wisconsin study in 2000-2001 compared alfalfa yield with and without wheel traffic in eight states (Figure 1). Results show a 5-15% forage yield reduction for plots with wheel traffic for nearly all locations and years.
In a research study by D. Samac (USDA-ARS, Univ. of Minn.) comparing alfalfa wheel traffic versus no wheel traffic (Figure 2), yield reductions ranged from 5-26% averaged across locations and years.
By rating crown rot damage, researchers could measure the impact of wheel traffic on alfalfa plant health. At both locations, crown rot severity was 20% higher in plots that had wheel traffic as compared to no wheel traffic, contributing to a 15% reduction in final stand counts at the end of two years.
Several factors affect severity of wheel traffic damage in alfalfa.
The following alfalfa harvest management practices can help reduce yield and stand losses due to wheel traffic.
The foregoing is provided for informational purposes only. Please consult with your nutritionist or veterinarian for suggestions specific to your operation. Product performance is variable and subject to a variety of environmental, disease, and pest pressures. Individual results may vary.
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