Photo: Chinese farm, north of Xi'an, below eroded terraces on the Loess Plateau. © 2017 Delena Norris-Tull
Crop Rotation
Summaries of the research and commentary by Dr. Delena Norris-Tull, Professor Emerita of Science Education, University of Montana Western, September 2020-2022.
Crop rotation is an agricultural practice that helps to reduce the spread of invasive plants. The World Economic Forum developed a report, Transforming Food Systems with Farmers, to assist the European Union nations in developing sustainable agricultural practices, practices the WEF calls Climate-Smart Agriculture. The report states that, "A meta-analysis found that farmers implementing just three climate-smart practices (no-till, cover crops and diversified crop rotations) could increase their profit by more than 11% and reduce the cost per hectare by 37% compared to conventional practices" (p.13).
Pulse crops in Montana, rotated with grains, helps break the disease cycle and reduce weeds, as well as restoring nitrogen to the soil. Pulses are also gluten-free crops. Pulses such as chickpeas are in high demand in the Middle East and China. Organic pulses sell at a high price. To change to organic farming, use alfalfa to restore nitrogen to the soil before you plant organic grains or pulses (interview on Montana Ag Live, March 31, 2019, Dean Folkvord, Founder of Wheat Montana Farms).
Incorporating cover crops within the cropping system “can provide many agronomic benefits, including improved nutrient cycling efficiency, pest suppression, soil and water quality, and cash-crop productivity….Crop rotations that utilize leguminous winter cover crop can also supplement N fertilizer inputs while producing crop yields comparable with conventional fertilizer-based systems and at the same time reduce N leaching up to 40%” (Curran, et al., 2015.) In the mid-Atlantic States, hairy vetch has potential as a useful cover crop, but it also can become weedy in the following crop, particularly if the next crop is winter wheat or another winter annual cereal. Curran, et al., 2015, compared the effectiveness of various herbicides in controlling hairy vetch, used as a cover crop, when winter wheat is used next in the crop rotation prior to summer planting of corn or soybean.
Which crop to use?
One factor that has discouraged farmers from incorporating crop rotation into their practice is the lack of adequate research on the impact of various rotational crops.
In California, the rice crop was severely reduced from 2021 to 2022, due to drought. Researchers at the University of California Davis have developed a new tool to assist rice farmers in using crop rotation to reduce losses due to drought. The crop rotation calculator enables farmers in the Sacramento Valley to project the economic impacts of using crops more tolerant of drought: dry beans, safflower, sunflower, and tomato. The research was funded by the USDA National Institute of Food and Agriculture, through a grant from the Western IPM Center.
Climate change is causing more frequent and more severe drought conditions in Western States. Tools that enable farmers to estimate the economic impact of diverse crops can assist them to select the most appropriate rotational crop for their fields.
Research on herbicide use within a crop rotation system
Data on the use of selective herbicides to control Vicia species during the crop phase of the rotation (rather than the more common practice of herbicide use before the cash-crop is planted) had not been studied. And hairy vetch had not been listed on labels for herbicides used for broadleaf weed control within winter wheat. Curran, et al., 2015, carried out a two-year experiment to determine which, and when applied, herbicides would work best to reduce hairy vetch within winter wheat, in the mid-Atlantic States of Pennsylvania and Maryland.
In early October, hairy vetch was planted first, with winter wheat planted immediately afterward. Nitrogen fertilization was applied before planting and at spring green-up. Fall post-emergent herbicides were applied in late fall (late November to early December). In the spring, additional fertilization was applied + spring herbicide. The following herbicide treatments were compared, when applied in late fall, after emergence of wheat and hairy vetch, and/or in spring (April): (1) synthetic auxins, (2) ALS inhibitors, (3) a protoporphyrinogen oxidase inhibitor, and (4) different combinations of 1 and 2.
Curran, et al., 2015, results: “Among synthetic auxins…, hairy vetch control was similarly high (>90%) after clopyralid, dicamba, or dicamb+2,4-D amine applied as either a fall or spring POST application. These herbicides were consistently effective for control of hairy vetch. A spring application of 2,4-D amine at 140g ha-1 resulted in better hairy vetch control (91%) compared with the fall application (41%).” A lower rate of 2,4-D amine, 70g ha-1, resulted in less than 75% control in both fall and spring timings. Curran has found that ester formulations of 2,4-D are better at hairy vetch control than amine formulations.
“Fall application of MCPA provided only 35 to 44% hairy vetch control.” Spring applications provided 59% control at lower rates, and 82% at higher rates. “With the exception of thifensulfuron applied alone, spring applications of ALS inhibitors…resulted in high (>90%) levels of hairy vetch control. Hairy vetch control after fall applications of ALS inhibitors was variable.”
Both fall and spring applications of prosulfuron and pyroxsulam were successful, with at least 95% control. “Fall application of mesosulfuron-methyl, thifensulfuron, tribenuron-methyl, and thifensulfuron/ tribenuron-methyl resulted in less than 75% hairy vetch control. Both fall and spring applications of thifensulfuron applied alone resulted in poor (<55%) hairy vetch control.” Fall and spring applications of the PPO inhibitor carfentrazone-ethyl had less than 75% control. Winter wheat injury was negligible for all treatments, with one exception. The spring application of 2,4-D amine resulted in 14% injury. Their report also provides details of a treatment-by-application timing effect on winter wheat yields. Depending on the timing of diverse chemicals, winter wheat yields were greater either in the fall or in the spring, usually related to instances of greater hairy vetch control.
Curran, et al., 2015, conclusions: The research verified that both a cover crop and the following cash-crop can be planted simultaneously and effectively treated with post-emergent herbicides. “Several synthetic auxin and ALS inhibitor herbicides, applied POST in fall or spring, can be safely used in winter wheat to control hairy vetch.” But some members of these herbicide families are not very effective. “Among synthetic auxins, clopyralid provided the most consistent control…at both application timings. Dicamba applied alone or in combination with 2,4-D amine also provided consistent… control at both application timings… Among ALS inhibitors, pyroxsulam and prosulfuron provided the most consistent control… at both application timings…. In separate research…, simulated inversion tillage significantly reduced hairy vetch seedling emergence and increased seed bank loss in comparison with shallow-placed seed bank.”
References:
Links to additional Agricultural Best Practices:
Links to more Innovative Solutions:
Crop Rotation
Summaries of the research and commentary by Dr. Delena Norris-Tull, Professor Emerita of Science Education, University of Montana Western, September 2020-2022.
Crop rotation is an agricultural practice that helps to reduce the spread of invasive plants. The World Economic Forum developed a report, Transforming Food Systems with Farmers, to assist the European Union nations in developing sustainable agricultural practices, practices the WEF calls Climate-Smart Agriculture. The report states that, "A meta-analysis found that farmers implementing just three climate-smart practices (no-till, cover crops and diversified crop rotations) could increase their profit by more than 11% and reduce the cost per hectare by 37% compared to conventional practices" (p.13).
Pulse crops in Montana, rotated with grains, helps break the disease cycle and reduce weeds, as well as restoring nitrogen to the soil. Pulses are also gluten-free crops. Pulses such as chickpeas are in high demand in the Middle East and China. Organic pulses sell at a high price. To change to organic farming, use alfalfa to restore nitrogen to the soil before you plant organic grains or pulses (interview on Montana Ag Live, March 31, 2019, Dean Folkvord, Founder of Wheat Montana Farms).
Incorporating cover crops within the cropping system “can provide many agronomic benefits, including improved nutrient cycling efficiency, pest suppression, soil and water quality, and cash-crop productivity….Crop rotations that utilize leguminous winter cover crop can also supplement N fertilizer inputs while producing crop yields comparable with conventional fertilizer-based systems and at the same time reduce N leaching up to 40%” (Curran, et al., 2015.) In the mid-Atlantic States, hairy vetch has potential as a useful cover crop, but it also can become weedy in the following crop, particularly if the next crop is winter wheat or another winter annual cereal. Curran, et al., 2015, compared the effectiveness of various herbicides in controlling hairy vetch, used as a cover crop, when winter wheat is used next in the crop rotation prior to summer planting of corn or soybean.
Which crop to use?
One factor that has discouraged farmers from incorporating crop rotation into their practice is the lack of adequate research on the impact of various rotational crops.
In California, the rice crop was severely reduced from 2021 to 2022, due to drought. Researchers at the University of California Davis have developed a new tool to assist rice farmers in using crop rotation to reduce losses due to drought. The crop rotation calculator enables farmers in the Sacramento Valley to project the economic impacts of using crops more tolerant of drought: dry beans, safflower, sunflower, and tomato. The research was funded by the USDA National Institute of Food and Agriculture, through a grant from the Western IPM Center.
Climate change is causing more frequent and more severe drought conditions in Western States. Tools that enable farmers to estimate the economic impact of diverse crops can assist them to select the most appropriate rotational crop for their fields.
Research on herbicide use within a crop rotation system
Data on the use of selective herbicides to control Vicia species during the crop phase of the rotation (rather than the more common practice of herbicide use before the cash-crop is planted) had not been studied. And hairy vetch had not been listed on labels for herbicides used for broadleaf weed control within winter wheat. Curran, et al., 2015, carried out a two-year experiment to determine which, and when applied, herbicides would work best to reduce hairy vetch within winter wheat, in the mid-Atlantic States of Pennsylvania and Maryland.
In early October, hairy vetch was planted first, with winter wheat planted immediately afterward. Nitrogen fertilization was applied before planting and at spring green-up. Fall post-emergent herbicides were applied in late fall (late November to early December). In the spring, additional fertilization was applied + spring herbicide. The following herbicide treatments were compared, when applied in late fall, after emergence of wheat and hairy vetch, and/or in spring (April): (1) synthetic auxins, (2) ALS inhibitors, (3) a protoporphyrinogen oxidase inhibitor, and (4) different combinations of 1 and 2.
Curran, et al., 2015, results: “Among synthetic auxins…, hairy vetch control was similarly high (>90%) after clopyralid, dicamba, or dicamb+2,4-D amine applied as either a fall or spring POST application. These herbicides were consistently effective for control of hairy vetch. A spring application of 2,4-D amine at 140g ha-1 resulted in better hairy vetch control (91%) compared with the fall application (41%).” A lower rate of 2,4-D amine, 70g ha-1, resulted in less than 75% control in both fall and spring timings. Curran has found that ester formulations of 2,4-D are better at hairy vetch control than amine formulations.
“Fall application of MCPA provided only 35 to 44% hairy vetch control.” Spring applications provided 59% control at lower rates, and 82% at higher rates. “With the exception of thifensulfuron applied alone, spring applications of ALS inhibitors…resulted in high (>90%) levels of hairy vetch control. Hairy vetch control after fall applications of ALS inhibitors was variable.”
Both fall and spring applications of prosulfuron and pyroxsulam were successful, with at least 95% control. “Fall application of mesosulfuron-methyl, thifensulfuron, tribenuron-methyl, and thifensulfuron/ tribenuron-methyl resulted in less than 75% hairy vetch control. Both fall and spring applications of thifensulfuron applied alone resulted in poor (<55%) hairy vetch control.” Fall and spring applications of the PPO inhibitor carfentrazone-ethyl had less than 75% control. Winter wheat injury was negligible for all treatments, with one exception. The spring application of 2,4-D amine resulted in 14% injury. Their report also provides details of a treatment-by-application timing effect on winter wheat yields. Depending on the timing of diverse chemicals, winter wheat yields were greater either in the fall or in the spring, usually related to instances of greater hairy vetch control.
Curran, et al., 2015, conclusions: The research verified that both a cover crop and the following cash-crop can be planted simultaneously and effectively treated with post-emergent herbicides. “Several synthetic auxin and ALS inhibitor herbicides, applied POST in fall or spring, can be safely used in winter wheat to control hairy vetch.” But some members of these herbicide families are not very effective. “Among synthetic auxins, clopyralid provided the most consistent control…at both application timings. Dicamba applied alone or in combination with 2,4-D amine also provided consistent… control at both application timings… Among ALS inhibitors, pyroxsulam and prosulfuron provided the most consistent control… at both application timings…. In separate research…, simulated inversion tillage significantly reduced hairy vetch seedling emergence and increased seed bank loss in comparison with shallow-placed seed bank.”
References:
- Curran, W.S., Wallace, J.M., Mirksy, S., & Crockett, B. (2015). Effectiveness of herbicides for control of hairy vetch (Vicia villosa) in winter wheat. Weed Technology, 29: 509-518.
- Hsu, M. (2022). New tool calculates crop rotation costs, benefits for California rice growers. California Ag Today. UCANR. https://californiaagtoday.com/new-tool-calculates-crop-rotation-costs-benefits-for-california-rice-growers/
- World Economic Forum. (April 2022). Transforming Food Systems with Farmers: A Pathway for the EU. World Economic Forum, in collaboration with Deloitte & NTT Data. https://www.weforum.org/reports/transforming-food-systems-with-farmers-a-pathway-for-the-eu
Links to additional Agricultural Best Practices:
- Ecologically based Successional Management
- Perennial Crops, Intercropping, beneficial insects
- Soil Solarization
- Natural Farming
- Permaculture
- Organic Farming
- Embedding Natural Habitats
- Conservation Tillage
- Water Use Practices
- Tree Planting: Pros & Cons
Links to more Innovative Solutions: