Beet quality improvement through nitrogen control

... TO: FROM: SUBJECT: MEMORANDUM May 12, 1972 Larry McGhee T.J. Ar~ \

Beet Quality Improvement Through Nitrogen Control --L. H. Henderson

The article put together by Leonard is excellent. We definitely should get some mileage out of this type of material.

Perhaps the Nebraska Farmer, Colorado Farmer and similar magazines could use this in their next issue. We can get you some good photographs of the equipment. Leonard probably has photographs of his crews in action. These would be even better.

TJA:jmg

BEET QUALITY IMPROVEMENT THROUGH NITROGEN CONTROL

I:.. H. Henderson

This means providing the growing sugar beet with the amount of nitrogen it needs to produce maximum tonnage while at the same time limiting the nitrogen so that the beet will be high in sugar at harvest. If the supply is too small, the crop starves and quits growing before the season ends. The result is that tonnage is cut short and although the sugar percent will probably be high, the yield will be low and the grower and the Company both suffer from insufficient production.

To make our business healthy we need maximum production. To the Sugar Company that means a large supply of beets. This, in turn, means maximum plantings. Growers provide such plantings only if they can expect optimum returns. Optimum returns depend upon maximum yields and price. Maximum yields depend, in addition to other things, upon sufficient fertility. The price depends upon sugar content. Sugar content depends ·upon:

1. The year. Some years are just naturally good. 2. The stand. (Plant population per acre.)

3. Climatic conditions and storms . . (Hail - freeze) 4. Fertility.

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5. Harvesting dates and pace of the harvest.

6. Disease and insect damage. (Rhizoc, leafspot, nematode) 7. Variety of seed.

It is readily obvious to everyone that only a few of these factors are within our control.

Low sugar·contents reduce our ability. to extract the.sugar, but we must remind ourselves at the outset that some of our extraction problems are due to factors other than low sugar content beets and that when we solve that, we have only corrected a part of the whole problem.

Because we know that an excess of nitrogen in the soil causes lower sugar content, we must control it. For many years nitrogen was a limiting factor in production, and on 50 percent of our Nebraska farms it still is. Prior to 1945 the feeding of livestock and a rotation of alfalfa or sweet clover provided the only source of nitrogen needed to produce a good beet crop. Twenty tons of beets per acre was the standard of excellence and usually the man who reached that goal followed that program.

In the 1940's commercial nitrogen fertilizers first made their appearance and in the 50's they really came into their own. Growers were urged to "maximize" their yields by using "all of the growing season." This was done by adding

commercial nitrogen as well as phosphate which already was standard practice.

--r Colored slides showing border effects in fields were used to motivate growers to

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~ add more nitrogen.

In the 60's an increasing acreage was planted to corn along with cheap nitrogen. The goal was 200 bushels per acre corn and 30-ton beets--all made possible by added commercial fertilizer, and corn particularly--responded to nitrogen. The more the better. Nitrogen used to cost 12¢ to 13¢ per unit. It got as cheap as 5¢ or 6¢ in the late 60's encouraging growers to use arnpl~ supplies of it.

Fertilizer dealers sampled fields as a free service. They sampled each field to the depth of the plow sole, usually 811

- 10", and shipped samples to a

number of commercial laboratories who prescribed all kinds of nutrients including the micro nutrients. In some cases the laboratory that recommended the highest

rates of fert111zer got the most business.

Sugar contents declined. Yields went up. Twenty-five tons per acre beets and 13% sugar were all too common.

Finally, soil researchers began measuring residual nitrate nitrogen in Western soils and its effect on various crops.

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University. Other soils men had been studying nitrogen build-up in soils but our first formal introduction to the idea was by Dr. Reuss in 1971.

The balance of this discussion will be a progress report on our soil testing program as a guide to fertilizing sugar beets.

Following Dr. Reuss' presentation at our winter ag meetings, we embarked upon the soil sampling program with the help of. the University of Nebraska soils department. The program was designed to tell us within practical limits just how

much nitrogen was available in a given field. Through this system of sampling and testing it was hoped .that we would know whether or not a field needed added nitrogen to produce a crop of beets and if so, how much.

The first thing we learned from the people at the University of Nebraska was that we would ·be wasting our time sampling our soils to a depth of only 2411 which was being recommended in Colorado. Therefore, our agriculturalists started sampling 3611_{·deep with hand augers.}

Seventy-seven fields were sampled. It was not possible to take more samples in time for spring planting. Each 1211 _{increment of soil was tested} separately so the N03N level at each one foot depth was known.

The University soils laboratory ran the tests on all samples and forwarded the results to the extension soils specialist at the University's Scottsbluff

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Station. He then made fertilizer recommendations to growers based upon the tests. He worked very closely with company agricultural administrators and agriculturists. The time required to get the test results varies with the volume of work the lab has, but averages about two weeks.

The results obtained from this limited number of samples was so interest-ing that we determined to enlarge our samplinterest-ing program in the fall for the plantinterest-ing in 1972. We were finding lots of nitrogen in fields that were chronic low sugar producers. Pounds of nitrogen per acre in those three foot profiles varied all the way from 14 pounds to 249 pounds nitrogen per acre. The accepted rule for nitrogen requirements is ten pounds of nitrogen per each ton of beets desired. The field . ~ with 249 pounds of nitrogen per acre,

~ ( without any additional fertilization.

therefore, already had an excess of nitrogen

Re~lizing that the statistical data to back our position was woefully inadequate we nevertheless urged all low sugar content growers to reduce the n1-trogen rates for beet grouhd.' This advice was based upon our knowledge of the farm's history of producing low sugar c?ntent beets and the grower's record of heavy fertilization, further whetted by the results obtained from the meager sam-pling done that spring. Our knowledge was backed up to a point by preliminary results of deep nitrogen studies that had been carried on at the Scottsbluff

station by Frank Anderson and although his·experiments were not completed at that time, they influenced our judgement and reinforced_our confidence.

Fertilizer dealers in this area were understandably alarmed at this turn of events and to encourage their cooperation and invite their participation, we called a meeting with all of them in this area to explain our position and the nitrogen control program. The meeting was succ~ssful because they learned first-hand what we were about and while they probably questioned some of our recommenda-tions, they could not question our motives. They also understood they could not long stay in business selling a product that was not needed and even was harmful when used in excess., Moreover it was pointed out that over one-half the fields

sampled required additional amounts of nitrogen and we were recommending not applying nitrogen only to those fields that had an excess.

The sampling ·of fields for 1972 plantings commenced about two weeks

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~ before the 1971 beet harvest started. Two men were hired to sample fields. A

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_{hydraulic probe sampler was used and a total of 253 fields were sampled during the}

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fall. Sampling ~as completed about Thanksgiving.

Several experimental samplings were made on high and low sugar content beet fields ·just harvested to give an inkling of how nitrogen and sugar percent correlated. The answers were surprising and the only course remaining was.to

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sample deeper. A test was therefore designed using fifty of the commercial fields

that had been already sampled. They were selected by comparing _{N03N contents per}

foot in the one, two, and three foot depths. Fields were selected that were

sus-pected of having additional amounts of nitrogen at the 4', 5', and 6' levels. These

samples could not be taken until spring but the results of the tests have confirmed

our suspicions as significant amounts of nitrogen were found at the lower levels.

The fifty fields averaged 145.42 pounds nitrogen per acre in the top 3611

and an additional 51.7 pounds per acre in the 3611 _{to 72}11 _{profile, bringing the total}

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nitrogen per acre to 197.12 lbs or enough to produce a 20-ton per acre crop.

These results gave us additional assurance so that we were more confident

in recommending that growers apply less nitrogen.

It must be remembered because of the lag time between sampling the fields

and obtaining the ·test results from the University lab, that growers were anxious

to ferti"lize before spring tests were available. Our policy was to reduce nitrogen

applications even without test results.

We were still uncomfortable to be taking recommendations to the field

that weren't adequately supported by research. Nevertheless, our need to improve

sugar content was so1great that we took the calculated risk without the proof we

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sugar and the company was suffering the consequences of lowering purities and declining extractions. Growers were blaming the seed varieties and some were

threatening to go out of the beet business.

We asked our G. W. Research Center for proof that residual nitrogen in

soils was a fact and that excessive amounts could be measured, but they had none. We asked them to get some and they responded by·setting up a study of selected high and low sugar content fields. Forty of these fields were sampled for residual

nitrates in Nebraska this spring and this information plus the results from the 50 special fields sampled to the 6-foot depth and the 3-foot samples from over 250 commercial fields now provide us with valuable additional information. See the

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attached tables.

To complete our study this year our agriculturists will have the actual pounds of nitrogen applied to each of the sampled fields. The 50 special fields wi11 be sampled for petiole testing at the appropriate time this summer. This

information plus the careful tabulation of sugar contents and yields from the sampled fields this fall should provide 'much needed information.

We have seen enough evidence to convince us that the practical method to determine fertilizer needs is to sample each field to a depth of six feet or to the impervious layer if that is less.

Our growers will continue to grow corn in the rotation with beets and

they will very likely continue to increase the rate of nitrogen applied to corn to

insure maximum corn yields. These fields should be tested for residual nitrogen

prior to planting beets.

I believe we should purchase two additional hydraulic samplers for

Nebraska and commence custom commercial sampling as soon as soil temperatures

are satisfactory and fields are ready this fall.

The cost of such sampling will probably run in the neighborhood of $20

per field. Growers will not hesitate to pay this amount and we can well afford to

pick up the extra cost if an~ because of the benefits we will receive from the

improved quality of beet that will result.

The best way to make this program work is to continue our cooperative

effort with the University of Nebraska. Their people are eminently well qualified.

They are not trying to .~ell beet acreage or fertilizer and their recommendations

will be accepted by most of oµr growers.

It should be pretty. obvious to everyone that we are really running ahead

of our research on this program and that additional basic knowledge is needed.

Specifically, our ~nowledge regarding the proper handling of samples from the

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on a moist sample collected in the morning and carried aro~nd in the cab of a pickup until evening before it is spread out to air dry? \~hat soil temperatures are satisfactory for sampling? How much variation in nitrogen content can be

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expected from the sampling procedure itself?

Frank Anderson, Assistant Professor, University of Nebraska, is re-searching available reports on these problems now and has planned a number of research tests for this year to augment the p~evious work and provide the additional information needed to answer these questions.

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