Weather, Climate Change and Agricultural Resiliency
September 8, 2017
The 2017 growing season has proven one of the most challenging in recent memory and portends things to come. Precipitation in particular has been highly variable, including periods of excess rainfall, waterlogged soils and now a prolonged dry spell. Agriculturally, results from this pattern were difficulty getting spring field done during brief 1 to 3-day periods of dry conditions, nutrient losses caused by saturated soils and now, moisture stress because crops exposed to wet conditions early in the season don’t develop the extensive root systems needed when soil moisture is limited later. A windshield survey of crop condition almost anywhere in Wisconsin shows these problems are widespread.
There’s no doubt that climate change will lead to greater weather variability, including increased frequency and intensity of rainfall events as well as prolonged dry periods, both affecting agricultural productivity. So what’s the difference between weather and climate? Weather is what’s happening right now, climate is the longer-term view, trends over successive years. For climate change doubters, it’s easy to dismiss extremes as weather, but the data shows otherwise. Figure 1 shows long-term precipitation data from one of our local research sites, both season-long total compared to average, but more importantly, monthly totals for June, July and August when moisture is critical for crops to reach their yield potential. Beginning in 2007, precipitation patterns are noticeably more variable, leading to periods of excess and deficiency. Statistically, June and August are the most variable months, while July, often thought of as the dry month, is often highly variable. Consider 2017, 10.5 inches of rain fell at this site, much more at others locally, and by the 31st, we exceeded the season-average (April through October) total rainfall.
Extreme rainfall events in succession can be devastating for crops, the soil resource and water quality as water-logged soil shed excess water, moving soil and nutrients downstream. Figure 2 illustrates this point, showing field flooding and devastating surface flow in a Rock County field in June 2008 where 12 inches of rain fell during the month. Extensive soil moving was required to repair the damage and make the field farmable again and the crop was lost in a widely affected area.
The upshot: We need to develop farming systems which are resilient in face of this variability. Strategies include improving soil health to enable plants to better deal with stress, cover cropping to increase infiltration and reduce erosion while reducing evaporation during dry periods and no-till methods for organic production to combine these benefits. All three are priorities of our Institutes research program. In particular, we are working on no-till systems, organic and conventional, which reduce soil erodibility, allow development of stable macropores to increase infiltration, and produce a surface residue mat which conserves soil moisture during dry periods.
Figure 2. Field flooding and runoff, Rock County, June 2008.