Crop Diversity to Enhance Resilience to Extreme Weather

How does climate change influence milk?
The next time you drink organic milk, think about the dairy cows and the forage they consume; growing this forage is disturbed by extreme weather events due to climate change. Organic dairy is an important industry in the Northeast because the majority of the nation’s organic dairy farms are here, producing 20% of the nation’s organic milk. In the Northeast, the predominant organic dairy forage system is based on cool season perennial grass and legume species, which become stressed by heat and drought. Extreme rainfalls and intense heat have increased in frequency and magnitude recently. These stress forage production and impact dairy operations.

At the Sustainable Cropping Systems Lab, we’re researching two strategies for forage cropping that can help dairy farmers be resilient against climate change: 1) intercropping and 2) double-cropping.

Intercropping is growing multiple crops at the same time, for instance sudangrass, sorghum sudangrass, forage corn, and pearl millet—instead of just a single crop. Increased resilience from intercropping forage mixtures can be attributed to complementarity among species with differing traits and a greater probability of having at least one species that responds positively to any environmental condition. Over the long-term, growing a diverse mixture is a better strategy than choosing the species that initially produces the greatest biomass because of variability in environmental conditions. Increased diversity also lowers the risk of pest and disease problems and increases so microbial diversity.

Double cropping
Double cropping is growing two or more crops on the same land in a single growing season. Annual crops, like triticale, pearl millet, and sorghum sudangrass could be seeded in early summer and can be harvested multiple times to provide a window of opportunity in late summer to establish a winter annual forage crop. A winter annual (like cereal rye or winter pea) keeps the soil covered over the winter. Double crops also give farmers flexibility to be responsive to an extreme weather event in case one happens—they already have a plan in place for the following few months. Production of annual crops could help supplement periods of low perennial forage production by ensuring the availability of high-quality forage crops during periods of low cool season forage productivity. Growing annual forage crops with perennials can increase forage reserves and build resilience.

Ecological Concepts
Cropping systems are like stock portfolios, the more diversified they are, the less risky they are. Absorptive capacity helps a cropping system absorb risk (e.g. — intercropping, improving soil health, irrigation). Adaptive capacity helps a farmer be responsive to an extreme weather event (e.g. — double-cropping, planting an “emergency forage”), and restorative capacity helps a farmer continue farming after crop failure (e.g. — crop insurance, disaster payments).

Resilience capacity (left) and the timing of double cropping (right) are illustrated below. Overall resilience capacity is maximized with redundancy within and among adaptive, absorptive, and restorative capacity components.

We will increase the resilience of organic farming systems in the Northeast through research and development of these three complementary risk management strategies, Intercropping, Double Cropping, and crop insurance. Each strategy enhances a different component of farm resilience.

Our Experiment
The experiment is replicated at University of Vermont and University of New Hampshire in addition to the Cornell Musgrave Research Farm. All sites compare two management systems: the standard Perennial Forage system and a novel Double Crop system. In each system, we will test the effects of forage diversity with four diversity treatments (see below table): 1) Low Diversity; 2) Intraspecific Diversity; 3) Interspecific Diversity; and 4) High Diversity. We are studying both Intraspecific and Interspecific diversity to explore the questions: can genetic diversity in the field help? Or does diversity only matter when different species are involved?

We hypothesize that the Double Crop system will be more stable, and at least as productive and profitable as the Perennial Forage system. This is to say: forage crop mixtures with multiple varieties and species will be more productive and stable (i.e., less variable in terms of dry matter production) across sites and over time than will forage crop monocultures. However, our goal here is not to determine simply which system is “better” than the other, instead we aim to make recommendations for which system will be better suited to certain circumstances.

We aim to reduce the negative impacts from extreme weather for organic dairy farmers.

We planted the experiment in summer of 2016 and it will continue for four years with two rounds of double cropping. Mixtures were seeded using a replacement design based on their monoculture rate. We will examine soil health parameters associated with the different forage cropping systems, forage yield, and profitability. Our most elaborate test in fall 2016 was for soil enzymes; after collection the soil samples were passed through a sieve and then mailed overnight on ice to the research lab. We are interested in how plant diversity affects soil microbial diversity.

We look forward to summer 2017 and the first full season of data collection.




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