Potato response to additional nitrogen + grab-bag from the news

Potatoes and fertilizer

Michael, the sometimes anonymous, asked some questions about potatoes and nitrogen rates 

Most crops will show linear, positive responses when a "bottleneck" nutrient is supplemented in moderate amounts. As the supplementation is increased, there comes point when other variables bottle-necking production more than the nutrient of interest. While the crop might still show a positive response, the increment of gain decreases as incremental amounts of the (formerly bottle-necking) nutrient increase.

Traditionally, growers would stop increasing the amount of added nutrient at the point where the income of the incremental production equaled the cost of the incremental nutrient input.

More recently, external costs like nutrient leaching into surface and ground-water have been considered and nutrient use efficiency (how much ends up in the plant) has been added into the equation. From a macro-scale, if you are approaching saturation and your neighbor is far short of it, society is best served if your neighbor applies the nutrient because he will get a higher incremental return on the investment. That is, more food will be produced in-aggregate, if all producers stop adding the nutrient when it hits the same incremental gain/incremental amount applied.

"Sensitivity" is a useful concept for the small grower. That is the incremental production that can be expected per unit-of-added nutrient. The underlying assumptions are important to understand. There is no point in adding more nitrogen, for instance, if your primary bottleneck is lack of moisture in the soil or lack of sunlight.

In Michigan, potatoes/urea can be expected to have a sensitivity of 150:1. That is, if nitrogen is the bottleneck nutrient then each unit of urea added to the potato-patch can be expected to produce an incremental 150 units of potatoes. As long as the total amount of nitrogen available to the potato plants doesn't approach the levels where it exceeds what the plant can absorb and use, that  number is insensitive to the area the urea is spread over and fairly insensitive to whether you planted the potato plants 6" apart in the rows or 18" apart in the rows. I expect this information to be applicable to regions in the United States north of Interstate 70.

"Saturation" depicted by the yellow region where incremental response is functionally almost zero

Actual numbers. Picture a row of potatoes that is 33 feet long (roughly 10 meters) with the rows 40" apart (about one meter). If the soil was totally devoid of nitrogen then one pound of urea, if applied at appropriate times, will be nibbling at the lower end of the saturation level...in Michigan using vigorous, mid or late-season varieties.

That same row of potatoes planted in good garden soil might only get half as much nitrogen as they can use. In that case, adding up to half-a-pound of urea per 33 feet of row will still provide the magical, linear, incremental-response of 150 pounds of potatoes for every pound of urea added.

If you live where metric is king, one kg of urea for every 20 meters of row for horrible dirt and 1/2 kg of urea for every 20 meters will still give you the 150:1 response.

This table shows the yield that commercial potato growers in Michigan can expect from various application rates for nitrogen. 10,000 additional pounds of potatoes for each additional 30 pounds of N. This table and the next table are from MSU E-2779.

If you think in terms of square-feet, 1000 square-feet of potato patch on decent garden soil can probably absorb 5 pounds of urea (an incremental rate of 100 additional pounds of N per acre) with a net increase in yield of about 750 pounds of potatoes/1000 square-feet.

Caveat: Some of the potatoes will be small, some will be lumpy, some might have deep eyes, some are likely to have "hollow heart". The incremental 750 pounds of potatoes will be edible but they will not all be pretty. You still need to control insects and weeds and provide water when necessary.

Applying N several times through the season reduces losses due to leaching (sand). Remember, you have to add it BEFORE the plant needs it. It takes time to percolate to the root-zone and be absorbed by the plant.

To answer the question Michael asked, I think the unfertilized soil was only supplying 1/3 of the N the plants could use. If I had fertilized at optimum rate (another 7 lb urea per 1000 square-feet for that patch of garden) I would be harvesting 3X the pounds of potatoes with no additional tilling, seed potato planted, weeding or number of shovel-fulls of dirt to dig them. That is a very attractive pay-back rate.

Grab bag

A sample of various countries showing the percentage of their Consumer Price Index that is Energy (X axis) and Food (Y axis)

 

NYT downplayed their actions calling it "an honest mistake". They did not publish a retraction until after Spears filed a lawsuit. Sounds like they DNGAS about accuracy until it looked like it might cost them money.

The reporter had integrity. He left the "News" organization when it refused to present both sides of a volatile issue. Seattle.

I might not be a lawyer, but that looks like "inciting violence" to me. Antifa claims to be totally decentralized but that does not pass the smell test.