Crop mergers: Management of soil contamination and leaf loss in alfalfa

Authors: Digman, Matthew; SHINNERS, KEVIN - University Of Wisconsin; Boettcher, Michael

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/11/2012
Publication Date: 2/1/2013
Citation: Digman, M.F., Shinners, K.J., Boettcher, M.E. 2013. Crop mergers: Management of soil contamination and leaf loss in alfalfa. Applied Engineering in Agriculture. 29(2):179-185.

Interpretive Summary: Maximizing the capacity and subsequent efficiency of the forage harvester necessitates consolidation (raking or merging) of alfalfa cuttings. However, the consolidation process can lead to field losses and contamination of the crop with soil (ash). When making silage, incorporation of ash is detrimental to the cutting mechanism of the baler and forage harvester. Furthermore, clostridia bacteria incorporated with soil can poison the fermentation process, resulting in a poor quality, potentially poisonous silage. Previous research on crop consolidation is limited to rakes and inverters and not modern merger designs or harvesting practices. In this study, field capacity, leaf loss, and the extent of ash (soil) incorporated into windrows were investigated by on-farm observation and through a controlled experiment. Based on this work: 1) even under poor management conditions, the merging process does not lead to appreciable contamination of the windrow with ash; 2) currently recommended cutting practices minimize ash; 3) with silage making, higher moisture levels at the time of consolidation minimize losses to 1% of harvestable yield; 4) fuel rate for the merging process is currently being minimized by the operator, but current merger designs limit their ability to manage fuel use; and 5) current engineering models over-predict fuel use for crop consolidation. This work provides the forage producer with research-based practices to manage forage quality, increase harvester productivity, and reduce environmental impact, all of which will improve his or her competitiveness. Finally, the energy use and productivity data can be used to improve the economic analyses associated with forage harvesting systems.

Technical Abstract: Maximizing the capacity and subsequent efficiency of the forage harvester necessitates consolidation (raking or merging) of alfalfa cuttings. Although rotary rakes are in wide use, the use of continuous pickup belt mergers is increasing in the Midwestern U.S. Previous work on crop consolidation is limited to rakes and inverters available during the time period and, therefore, does not consider modern merger designs or harvesting practices. In this study, field capacity, leaf loss, and the extent of ash (soil) incorporated into windrows was investigated by on-farm observation and through a controlled experiment. The experimental portion employed a factorial design to study the influence of two moisture levels (60 and 40% w.b.) and three cutting heights (5.1, 7.6, and 10.2 cm) on the ash incorporation and leaf loss of a belt merger. In the controlled experiment, windrow ash content increased statistically, but not practically, with lower cutting heights and lower swath moisture. Managing windrow ash with cutting height resulted in an average yield loss of 0.3 Mg ha-1 cm-1. Leaf loss was observed to increase with decreased swath moisture from 1.1 to 2.2% of total biomass. The on-farm survey included four operations including two owner-operators and two custom-operators, as well as five separate machine-tractor-operator combinations. Here, a variety of merging practices were revealed, yielding a range of theoretical field capacities from 13.2 to 16.9 ha h-1. Each operation managed tractor engine speed below rated PTO speed, resulting in fuel rates between 18.2 and 21.3 L h-1, which were less than predicted by ASABE models. As with the experimental work, the use of a belt type merger did not cause significant amounts of windrow contamination.