ARS | Publication request: Using Green Manure to Enhance POtato Production: II, Other Bnenefits -Effects on Nutrient Cycling, Tuber Yield and Quality

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: January 22, 2007
Publication Date: January 30, 2007
Citation: Delgado, J.A., Essah, S., Dillon, M., Ingahn, R., Manter, D.K., Stuebe, A., Sparks, R. 2007. Using Green Manure to Enhance POtato Production: II, Other Bnenefits -Effects on Nutrient Cycling, Tuber Yield and Quality. 24th Annual Potato/Grain Conference, Jan. 30 - Feb. 2, 2007, Colorado State University, Monte Vista, CO.

Interpretive Summary: Colorado’s San Luis Valley (SLV) is one of the leading producing areas of fresh market potatoes in the U.S.A. and produces over ninety percent of the state’s potatoes. In this region, potatoes are grown under center-pivot irrigated sandy soils that have low soil organic matter and micronutrient content. Micro-nutrients can be a problem in this region of high pH sandy soils for crops that are susceptible to Fe, Mn, and Zn deficiencies. Another concern for this region is the drought that reduced the recharge of underground water resources. Due to the recent drought, it has been recommended to cut back on the amount of irrigated acreage. It is important to develop irrigation alternatives so limited irrigation can be viable for farmers and contribute to sustainable systems across region (Hu et al. 2005). Additionally, irrigated sandy soils are susceptible to nitrate leaching. Cover crop dry biomass production and nutrient uptake studies were conducted from 2003 to 2006. Two years studies have been conducted to monitor the effect of the cover crops on the following potato crop. Mustard, radish, and canola had higher Ca content than the sorghum-sudan. Sorghum-sudan extracted twice the amount of Cu and Mn than radish, canola, or mustard. Additionally, sorghum-sudan Zn content was higher than that of the mustard and canola. Cover crops can be used as green manures to cycle nutrients to other important crops. Under commercial farm operations, the total marketable tuber yield was increased by 12 to 30% when potatoes followed a sorghum-sudan green manure instead of wet fallow plots. For the potatoes following sorghum-sudan, there was superior tuber quality, with 40% higher production, for tubers greater than 8 ounces when compared to tuber quality and production rates that followed a wet fallow plot. Additionally sorghum-sudan hay also increased tuber yield and tuber quality. These preliminary results conducted under commercial field studies show that there is potential to generate additional income ($60.00 to $400.00 dollars per acre), which would more than offset the cost and management of the cover crop. The farmer will have the option of harvesting the sorghum-sudan or incorporate the sorghum-sudan as a green manure. These studies show that green manure crops can provide farmers with a viable alternative to ensure sustainability of water resources, conservation of soil, increase in yields, and even increase in tuber quality. One particular green manure cover crop that is proving a viable economical alternative is sorghum-sudan. We suggest that users could add winter cover rye after the potato crop to minimize erosion prior to planting sorghum-sudan.

Technical Abstract: Colorado’s San Luis Valley (SLV) is one of the leading producing areas of fresh market potatoes in the U.S.A. and produces over ninety percent of the state’s potatoes. In this region, potatoes are grown under center-pivot irrigated sandy soils that have low soil organic matter and micronutrient content. Micro-nutrients can be a problem in this region of high pH sandy soils for crops that are susceptible to Fe, Mn, and Zn deficiencies. Cover crop dry biomass production and nutrient uptake studies were conducted from 2003 to 2006. Two years studies have been conducted to monitor the effect of the cover crops on the following potato crop. Mustard, radish, and canola had higher Ca content than The sorghum-sudan, mustard, radish, and canola average dry matter production with limited irrigation was 3000, 4300, 4500, and 6261 lbs per acre, respectively. These cover crops were produced with an average of 17 cm of irrigation, 25 to 30 cm (10 to 12 inches) less than for a barley or potato crop. The farmer will have the option to grow the cover crop with limited irrigation and have the alternative of using the aboveground biomass for hay (sorghum-sudan) or incorporating it as a green manure crop. Mustard, radish, and canola had higher Ca content than the sorghum-sudan. Sorghum-sudan extracted twice the amount of Cu and Mn than radish, canola, or mustard. Additionally, sorghum-sudan Zn content was higher than that of the mustard and canola. Cover crops can be used as green manures to cycle nutrients to other important crops. Under commercial farm operations, the total marketable tuber yield was increased by 12 to 30% when potatoes followed a sorghum-sudan green manure instead of wet fallow plots. For the potatoes following sorghum-sudan, there was superior tuber quality, with 40% higher production, for tubers greater than 8 ounces when compared to tuber quality and production rates that followed a wet fallow plot. Sorghum-sudan increased the macro and micro nutrient uptake of potato tubers. The Cu, Mn, and Zn use efficiencies of the sorghum-sudan cover crop was 4, 19, and 4%, respectively. The K, Ca, and Mg sorghum-sudan cover crop nutrient use efficiencies were 3, 22, and 40%, respectively. The Mn (r2=0.43) and Zn (r2=0.48) cover crop aboveground biomass uptake was correlated with tuber yield (P<0.05). This data suggest that the cover crops are correcting micro-nutrients deficiencies for these high pH sandy soils with low organic matter content. These studies show that green manure crops can provide farmers with a viable alternative to ensure sustainability of water resources, conservation of soil, increase in yields, and even increase in tuber quality. One particular green manure cover crop that is proving a viable economical alternative is sorghum-sudan. We suggest that users could add winter cover rye after the potato crop to minimize erosion prior to planting sorghum-sudan.