Tobacco
Fertilization

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In spite of all the political problems and marketing concerns, tobacco is still our number one crop, and will continue to be for the foreseeable future. However, itís going to be less profitable, particularly in light of some of the lease prices being asked for, and paid, this year.

In 1997, a number of farmers in the county were involved in an extensive research project that looked at the profitability of producing tobacco. The results of this project showed some interesting numbers.

The top three costs (not including lease prices) were hired labor (at 24Ę/lb.), marketing charges (at 13Ę/lb.), and fertilization costs (at 9Ę/lb.).

 

There is a lot of potential for growers to substantially cut fertilization costs, and actually improve yields and quality of the crop. This month, Iíd like to focus on how you can manage your fertilization costs and still maintain top production.

Nutrients Needed by Tobacco

All plant life requires 17 elements to survive and grow. Nitrogen (N), phosphorus (P), and potassium (K) are the major elements needed, and the ones that we are concerned about.

The following chart shows the amount of nutrients that the plant removes from the field over the course of the growing season. Notice how little of it is used in the first month. That brings up a management concern Ė most of our nitrogen is put on the crop way before the crop needs it.

The next table shows the total amount of nutrients that are removed by a 3,000 lb. crop of tobacco. Compare that to the amount thatís typically used.

  Nutrients Removed by Crop of Tobacco 3000 lbs yield/acre Nutrients Supplied by Typical Fertilization 1 ton 5-10-15, 1000 lbs 33-0-0
N 200 430
P2O5 35 200
K2O 210 300

As you can see, we put on way more fertilizer than we need. The extra nitrogen is lost, mostly through leaching down through the soil out of reach of the plant roots, where it eventually gets into the groundwater, causing some environmental problems. Phosphate and potash stay where they are, and just continue to build up to higher and higher levels. Because of this massive over-fertilization, soil test levels of these two nutrients are extremely high in many tobacco fields. 75% of all tobacco soil test samples coming through my office need no phosphate fertilizer and one out of every four samples need no potash.

Reasons for Slow Tobacco Growth

I get a lot of calls over the course of each growing season Ė someoneís tobacco isnít growing very well, and they would like to find out why. Generally, many growersí first reaction is to add some ammonia nitrate to boost the growth. That may not be a good idea. Some potential reasons for slow tobacco growth are:

ß Dry weather                         ß Too little nitrogen
ß
Wet weather                        ß Too much nitrogen
ß
Cold soils                             ß Manganese toxicity
ß
Variety selection                 ß Root diseases

Out of this list, extra nitrogen will help one, maybe two of these problems, and it will aggravate at least two of the others.

Over the years, the single most common problem I see is manganese toxicity. Itís a problem with low pH. At various pH levels, essential elements become more or less available to plants, due to a chemical reaction with the soil.

 

 

Notice that nitrates become much less available as the pH goes down, which means with lower pH, the high-priced nitrogen you add isnít going to be as efficient for your crop. Some minor elements are essential to plant growth in very small doses, but too much can poison the plant. Thatís what happens with manganese.

Iíll argue that the very best fertilizer dollars you can spend on your crop is not for fertilizer, but for lime!

Lime on Tobacco

When using quarry lime, 90% of what you put on will be available in the soil within three years, and at least 35% of it will be available within one year. Often, Iíll get a question about using fine, bagged lime or pelleted lime in place of regular quarry lime. It will work, but you are paying a substantial premium for some of the convenience. Quarry lime runs $10-15/ton, fine lime is $45-50/ton, and pelleted lime is $90-100/ton. The fine lime is essentially the finer particles of the quarry lime, which is available in one year. In one $12 ton of quarry lime, youíre getting at least 700 lbs. of fine lime (about $16 worth), plus youíre getting the benefit of future availability. The pelleted lime is easier to spread, but recent research has shown that the pelleted form is not as fast acting as the powdered form.

My suggestions:

Nitrogen in Tobacco

Extensive studies over the years have shown that top yields come from a range of 200-250 lbs. of actual N per acre. This reflects what the plant is going to take up.

Weíve replicated these tests in Owen County over the last five years. While Owen County results show lower average yields (reflecting declining yields across the state and the fact that four out of the last five years had terrible growing conditions), the trend lime remains the same.

 

High nitrogen levels cause several problems:

X Leaf Quality: poor curing, bright colored leaf, and fat stems from excess nitrate salts.

X Environmental Problems: leaching of excess N into the groundwater.

X Disease Problems: the fast, lush growth from excess N is more susceptible to diseases.

X Management Problems: N is acid forming, leading to manganese toxicity, late applications keep plant from maturing properly, which, in turn, leads to quality problems.

X Waste of Money: if you apply too much, the excess is not going to stay in the soil; youíre going to lose it.

My suggestions:

Phosphate on Tobacco

Our soils are naturally very low in phosphate, but three out of every four tobacco soil tests test high in this plant nutrient. This reflects the fact that the 5-10-15 we have been using for years puts on much more phosphate than what plant uptake would suggest.

Since phosphate doesnít move through the soil, what you put on stays there. Youíre not going to lose it, but why pay for it now when you wonít need it for several years.

Also, some recent research has been pointing to phosphate as a major water pollutant, and we are likely going to be looking at some upcoming legal restrictions in the not too distant future relating to phosphate use, particularly in those fields where test levels are high.

My suggestions:

Potash on Tobacco

Weíve got something of a different situation with potash. We often run into problems with not enough of the nutrient in the soil.

Our soils in this Eden Hills region of the state are unique in that they tend to tie up potassium, making it somewhat unavailable for plant use, even though the soil might test fairly high. Consequently, soils testing less than medium-high and twice the potash than the rest of the state.

Potash fertilizer for tobacco is sold in a sulfate form, while potash for other crops is in a muriate form. Muriate of potash contains high levels of chlorine, which can drastically affect tobacco quality, causing it to retain water and hurting the burning qualities. However, it is cheaper than sulfate. It typically runs less than half the cost of sulfate, on a cost per pound of nutrient basis. There are legal restrictions on its use (no more than 50 lbs./Chlorine/acre/ season).

My suggestions:

 

Minor Nutrients                       

As mentioned earlier, plants need 17 elements to survive and grow. I already discussed the three big ones: N, P & K; and lime, which provides calcium.

A lot of research over the years has taken a look at the possible need for minor nutrients. In all these tests, there is only one nutrient, molydenum, which may need to be added. All the rest - the soil provides enough. There is no need for minor nutrient fertilization anywhere in the state of Kentucky. Years of research back up this statement.

Soil tests from commercial labs may come with the recommendation for small amounts of several minor nutrients. They base their recommendations on the amount of the nutrients that the plant uses. Itís a different recommendation philosophy than what the UK soil-testing lab has. The extra nutrients wonít hurt, they just wonít help. And, youíre paying for them!

Starter Fertilizer

A lot of growers are using a starter fertilizer in the transplant water. Thereís been some research on this, but it hasnít been conclusive as to whether this is really benefiting the crop.

Starter fertilizer contains very small amounts of actual nutrients, however, it gets a soluble solution that is high in phosphate concentrated right at the plant roots, ready for quick uptake. While the benefits arenít proven by research right now, I believe that it may be a good cheap form of insurance.

Foliar Fertilizer

A lot of people are using foliar fertilizers later in the growing season. Quite a bit of research has gone into this, too (including some Owen County research) and the results are crystal clear. There is NO benefit to this practice. It is a waste of time and money.

Very small amounts of actual nutrients are used with a foliar fertilizer. Typically, 20 lbs. of a 20-20-20 fertilizer is used. This provides a whopping 4 lbs. of N per acre. Compare that to the 250 lbs. of N needed by the crop. Youíd laugh in my face if I suggested putting on 12 lbs. of ammonia nitrate per acre (which is the equivalent amount).

This is enough nutrients to green up the crop, and thatís why itís so popular. However, thatís all itís doing Ė just making you feel good because itís greener! Itís not enough to cause any yield increase.

In closing, Iíd like to urge you to consider soil testing your tobacco crop ground this year.  If youíve not taken a soil sample before, call me or stop by and Iíll show you the procedure.  Bring the sample to the office, weíll send it off and Iíll make the fertilizer recommendation when it comes back.  Itís one of the best investments you could make and could potentially save you hundreds of dollars.  If you donít test it through the office, test it somewhere!  Itís the best money youíll spend on your tobacco crop this year.