"Is crop rotation practiced in America? I would have thought that a gap ofseveral years between a particular crop being planted, while others of different types, or grazing, in would greatly reduce the prevalence of pestsand the need for treatments." Chris
Chris, growing up on a farm after the dust bowl period, I was trained in rotation and strip farming. But I now see lots of changes - no till, continuous crop, elimination of strips. Also, as an entomologist, I know well that tilling exposes eggs and larvae of pests in the soil to the sun and dessication.
But what I learned is no longer the rule. In the corn belt, I've found areas of continuous corn - although Charles may disagree with me on this one, but that's what some growers in IN, IL, and NE told us.
In eastern Washington, wheat is grown right up to the edge of the pavement, steep slopes are farmed, and dust is severe at times. They even have modified the suspensions under the combines so that the harvesters can remain level on the steepest slopes. No strips planting at all.
The advent of precision agriculture mean that the harvesters can precisely monitor and map on GPS yield and variables such as protein content for the entire field. That data is then transferred to the planting, fertilizer applications - low yield spots get more seed and fertilizer, high yield areas may back off. And pesticides are mixed in the tank - regardless of the type or chemistry.
Good news, helicopters with gps and lasers flying at night can precisely spray. Bad news, in one study we did, we found that all of the helicopters carried tank mixes of several pesticides (insecticides, fungicides, sometimes herbicides - all intermixed). We wanted samples to see what was being applied to the fields in question - bees were flying over, wouldn't pollinate. But we couldn't get a tank or spray nozzle sample - CA regs made the systems more or less sealed to avoid drips and contamination.
Then again, we found large tanks in the Central Valley at the ends of fields. These contained fertilizer and sometimes pesticides that fed into the irrigation systems. In some areas, we saw flood irrigation, where the water was green, and catchments at the ends of the fields held green, brackish water for days after irrigating.
But the one issue that I think this list should discuss is chemigation. In CA, due to water restriction, in many orchards and more and more, we're seeing fields of crops like melons set up for drip irrigation. And, as soon as the drip systems go in, so does the feeding of fertilizer and pesticide mixtures into the water. Remember, drip systems are designed to leak - little puddles of water at each plant, and often leaks at junctions. Bees need water, and don't like fast flowing water, so guess where we see the bees?
We've spent weeks arguing about neonics. From my perspective, used as designed as a seed treatment, everything I've read or found in our own research indicates that treated seed represents low exposure risk. Dust from planters, can be a problem. Foliar spraying and tilling into soil defeats the minimal amount, targeted application of seed treatment and re-introduces larger amounts of chemical to the air, soil, etc.
But if you want to look at really serious problems, Tank Mixtures and Chemigation would be at the top of my list. Yet, I see little research or discussion of these topics.
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