Evaluation of a novel rotation of organically produced forage and a spring planted vegetable crop
Date
2010
Authors
Goldhamer, Daniel, author
Davis, J. G. (Jessica Gwyn), 1962-, advisor
Stonaker, Frank, committee member
Brummer, Joe E., committee member
Journal Title
Journal ISSN
Volume Title
Abstract
There are a limited number of organic forage producers in Colorado, thus organic dairies are faced with a shortage of high-quality, locally-produced organic forage. This study was conducted to explore warm-season forage production in rotation with a spring vegetable as a viable cropping system. In addition, effect of raw and composted dairy manure on soil quality was evaluated within this system. In order to evaluate the usefulness of annual forage crops in rotation with an organic vegetable, tef (Eragrostis tef Zucc.) and German millet (Setaria italica (L.) P. Beauv.) were seeded in the summers of 2008 and 2009, either alone or in combination with forage soybean (Glycine max L.) or sesbania (Sesbania macrocarpa Muhl. ex Raf.). The viability of these forage crops was evaluated in terms of their yield, crude protein (CP) content, neutral detergent fiber (NDF), acid detergent fiber (ADF) and weed composition. Forage yields ranged from 3960 kg ha-1 for tef alone to 7040 kg ha-1 for German millet alone. There was high weed pressure and low legume establishment. When German millet was planted alone, plots contained significantly lower weed biomass (29.8% in 2008 and 7.5% in 2009) than the other forage treatments which ranged between 26 and 60% weeds. Additionally, legume establishment in all plots was poor, accounting for at most 8.7% of the total yield by dry weight. Generally, tef had higher CP and NDF and ADF. Despite, the high concentration of weeds in the forage mixes, overall digestibility, as measured by a lower ADF content, was improved through the presence of weeds. Weed presence in forage has the potential to increase or decrease its quality depending on the weed species present and their concentration. In order to explore the effect of this rotation and additions of raw and composted dairy manure on soil quality, these organic inputs were applied in conjunction with the forage treatments and a control that received no soil amendments. Overall, the pH increased from 8.0 to 8.2 between years. This may have influenced the availability of macro and micro nutrients. Soil N and P were influenced by the fertility treatment by year interaction. There was higher soil NO3-N in 2008 in the manure treatment while there was no difference in soil NO3-N between the manure and compost treatments in 2009. Available soil P was higher in the manure treatment in 2008. Soil organic matter and particulate organic matter decreased with depth and year. This was possibly due to twice-yearly tillage within this system. Soil aggregation increased with depth for the >1000 μm and 500-1000 μm size classes and decreased with depth for the 53-250 μm size class. This warm-season forage production system may provide growers with an opportunity to expand their markets while also providing dairies with a local source of organic forage; however, the issues of weed control and legume establishment must be rectified. Overall, the inclusion of manure or compost application can increase soil quality; however, tillage must be minimized in order for significant gains to be realized.
Description
Department Head: Gary Peterson.
Rights Access
Subject
Forage plants -- Organic farming -- Colorado
Vegetables -- Organic farming -- Colorado
Crop rotation -- Colorado
Dairy cattle -- Manure -- Colorado