Soil Security
Recently (January 2023), Derpsch and seven other world soil scientist (Including retired Don Reicosky, USDA-ARS) wrote about declining soil productivity worldwide. These are their direct findings. Life on earth has been sustained for 3.8 billion years due to life supporting “natural laws”. Humans have tilled the soil for more than 10,000 years. These scientist found that most tillage operations are short terms solutions but create long term problems. Most of our soil problems are the result of tillage and trying to correct those problems, but it only gets worse, not better with more tillage.
A landmark study in 1995 by Pimmental and others, discovered that almost 1 Billion acres of farmable land or one-third the world’s farmable acreage had been lost to erosion. More than 95% of our food originates from soil and when soils degrade it threatens human survival. Derpsch and others (2006) outlined the negative effects of tillage. They include loss of soil organic matter (SOM) which holds soil nutrients, increased soil erosion, declining soil structure or increased soil compaction, reduced water infiltration, reduced drainage, increased water and nutrient runoff, and changes to soil biology (more soil bacteria, less fungi, less beneficial microbes, less predators that consume pests). When soils degrades, it contributes to decreased soil productivity, decrease crop yields and food insecurity. Agricultural sustainability or the conservation of our soils is critical to long-term human survival.
Some scientist and farmers naturally argue we can get better yields with more fertilizer, more pesticides, and more inputs. True short-term, but at what cost? At some point the loss of SOM and soil nutrients cause environmental problems with drinkable water, and increased disease or pests (both crops and human) due to harmful chemicals. Nature has natural solutions to these problems, maybe we need to learn and try to adapt to those “natural laws” first.
The soil scientist promote Conservation Agriculture (CA) which has three main natural laws. First, minimize or do no soil disturbance. Second, have permanent biomass on the soil surface. Most farmers think this is impossible on conventional tilled soils but on healthy CA soils, it works. Just look at your woods, pasture, fence lines, or long-term hay fields. Which has better soil properties, the conventional or the long-term CA soil? Third, maximize crop diversity which includes diversified crop rotations and long-term cover crop mixes. In a CA system, roots feed the microbes and the microbes feed the plants while they (roots, soil organisms) improve the soil together.
The following are the top ten reasons for tillage with a rebuttal to each one. Farmers till soil to plant their seed or crop. In healthy CA soils, direct seeding is possible with proper equipment modifications (especially sharp disc blades). Second, tillage is used to break up compacted layers (mostly from previous tillage operations). In CA systems, the increased SOM and improved soil structure are sponges that keep soils from compacting. Some farmers till to decrease soil crusting or to increase water infiltration short-term. Healthy soils do not have soil crusting issues and CA increases water infiltration long-term without tillage. Fifth, farmers till to remove vegetation and pests. In healthy CA, there are less pests including weeds, insects, and disease because the soil has natural predators that keep pests in check.
One benefit of tillage is that it warms the soil for spring planting. Cold water from the winter is removed by drying out the soil (0.5-1.0 inch per tillage pass). In healthy CA soils, water should naturally drain once compaction is removed and soil structure improves. This problem is the hardest and the longest to fix once a soil has been degraded. An alternative is to use strip till (20% tillage over the seed furrow, 80% no-till between the rows). Farmers use tillage to incorporate nutrients and to mix soil layers. In healthy CA, the good soil structure, high SOM, and improved water infiltration move nutrients into the soil where living roots (the crop followed by cover crop) keep nutrients recycling.
Finally, some farmers believe that tillage reduces soil erosion. If that is true, why has 1/3 of the world’s farming land eroded? Tillage dominates on most of our USA soils. The last one is a matter of pride. Clean fields, straight furrows, and satisfaction of doing a good hard day’s work after a tillage operation is a common theme. Maybe we need to learn to change our thinking on that matter. As one farmer told me, the first 40 acres may be fun to do tillage (the roars of the engine, the power) but after a while, the seat of the pants gets tired and the fuel bill keeps going up. Something to think about!