Fertilizer Guide for New Mexico

Guide A-128

Charles R. Glover, Extension Agronomist
R.D. Baker, Area Extension Agronomist

College of Agriculture and Home Economics, NMSU

Most New Mexico soils are not fertile enough to produce high yields without fertilizer. Decisions about fertilizer -- whether to apply it, what to select, and the amount to use -- affect the cost of production, yield, and farm income.

To select the kind and amount of fertilizer to use, growers need to know:

Fertility level as determined by soil test.
Soil type and capability.
Crop to be grown and desired yield.
Crops previously grown, yield obtained, and crop appearance.
Past fertilizer and management practices.
Quality and quantity of irrigation water.

Each soil has a combination of management practices under which it produces best. Successful farmers adjust their management practices from year to year and from soil to soil.

Fertilizer recommendations in this circular are general. Use them only as guides. Modify the rates of fertilizer applications suggested here by experience, local conditions, and management practices.

Much information about the capability of any soil and how it should be managed can be obtained from the county soil survey. Soil surveys have been completed for most New Mexico counties. These are available at the county agent's office and at the U.S. Department of Agriculture's Soil Conservation Service offices.

SOIL TESTING

It is desirable to have the soil in each field tested every 3 or 4 years, or more often if management practices change radically or when problem soils are involved. Soil can be tested at the Soil and Water Testing Laboratory, New Mexico State University. The local county agent has information sheets and instructions for sending samples for analysis.

A soil test is only as reliable as the sample sent to the laboratory. It is important the soil is sampled and handled properly to ensure good soil test results.

The basic steps in taking the sample and using the soil analyses are:

Divide the farm according to the fields of similar soils that receive similar treatments.
From each field, take 15 to 20 randomly spaced soil cores from the plow layers usually 9 inches. Mix.
Let the soil dry in the air.
Mark and label each sample. Keep an accurate record of where each sample originated.
Mail the completed information sheet with the soil sample.
Follow the recommendations on the report sheet the Soil Testing Laboratory sends to you, but leave a small unfertilized strip in the field to check the response to the fertilizer. (Fertilizer recommendations are based on the soil test results, information provided in the information sheet, and research findings.)
Keep a record of the results and compare them with the results from the unfertilized strip.

WHY FERTILIZE?

Each plant nutrient serves a specific purpose in helping plant growth and development.

NITROGEN

Nitrogen promotes vegetative growth of plants. A need for nitrogen may be indicated by slow growth and a pale green to yellow color. Although crops may not show these symptoms, it is often necessary to apply nitrogen for profitable yields.

Plants take up nitrogen primarily in the nitrate form, but they may also use ammonia. The nitrogen in most ammonium-containing fertilizers is rapidly converted to the nitrate form when added to the soil. Urea converts to ammonium, then to the nitrate form. This conversion is fast enough for plants to respond quickly to these types of nitrogen fertilizers. (Nitrogen in the form of urea or ammonia is less subject to leaching.)

Nitrogen should be applied as split applications rather than as a single application. Split applications allow for more efficient use of the fertilizer and reduces the injury from burn. In addition, split applications reduce the leaching of nitrates that may contaminate ground water.

PHOSPHORUS

Phosphorus helps plants develop good root systems, hastens maturity, and promotes fruiting. Many New Mexico soils are so deficient in phosphorus that vegetative growth is affected.

Phosphorus fertilizers should be applied to the soil in a soluble form. Insoluble phosphorus fertilizers, when added to the soil, are not converted to an available form and are of no practical value. There is evidence even soluble phosphorus fertilizers may become rapidly unavailable in alkaline soils.

POTASSIUM

Potassium increases the vigor and quality of the crop. Most New Mexico soils contain enough potassium for crop production. In the past, it has seldom been necessary to add this nutrient. However, on sandy soils and where high rates of nitrogen and phosphorus fertilizers are used, the addition of potassium may also be beneficial.

TRACE ELEMENTS

Carbon, hydrogen and oxygen are supplied from water and the air. Ten other nutrients essential for plant growth are commonly classified as secondary elements, and minor or trace elements, because they are needed in much smaller quantities. They are as essential to plant growth as the major elements.

Plants need some trace elements for photosynthesis, in which sunlight energy converts plant foods to the final carbohydrate, fat, and protein products found in mature plants. Although these trace elements may be needed in only small quantities, they are essential, and good yields cannot be obtained without them. Iron and zinc deficiencies are the most common in New Mexico.

Iron chlorosis, a result of iron deficiency, is common on many perennial ornamentals, fruit trees, sorghums, and lawns in New Mexico. The symptoms of iron deficiency are the yellowing of leaves with the veins of the leaves remaining green. The yellow usually appears first on new leaves. Iron deficiency can be helped with iron sulfate, acid-forming amendments, and iron chelates.

Zinc deficiency also causes a chlorotic condition similar to that caused by iron deficiency. Other symptoms are leaf rosette, the clustering together of leaves with short internodes on the terminal end of branches. In extreme cases, the leaf margin becomes irregular and the leaf becomes boat shaped. Die-back of tree twigs is common. Zinc deficiency is found principally in pecan and fruit orchards and on ornamentals. The deficiency symptoms can be corrected with applications of zinc sulfate or zinc chelate to the foliage, the soil, or both. Soil can be analyzed for iron and zinc content, but a trial application of zinc or iron on part of the crop is a good way to determine whether one of these elements is deficient.

WHAT'S IN THE BAG

The common plant nutrients in commercial fertilizers are nitrogen (N), phosphorus (P) and potassium (K). The pounds of each nutrient per 100 pounds of fertilizer are printed on the tag or on the bag in order, as nitrogen (N), phosphoric acid (P2O5) and potash (K2O). This is called the fertilizer formula. The nitrogen is labeled as an element, but the phosphorus and potassium have been labeled as oxides. For instance, a label of 8-8-8 means that there are 8 pounds of elemental nitrogen (N), 8 pounds of phosphorus pentoxide, commonly referred to as available phosphate (P2O5), and 8 pounds of potassium oxide, commonly referred to as soluble potash (K20), per 100 pounds fertilizer material.

Although phosphorus and potassium in fertilizers have been labeled as oxides for many years, fertilizer contains neither P2O5 nor K2O. Further, neither P2O5 nor K2O is involved in plant nutrition.

In most fertilizers, phosphorus is in a form of calcium ammonium phosphate. Plant roots usually take up the nutrient as the ortho-phosphate ion, H2P0 4^-. Potassium in fertilizers is most commonly either potassium sulfate or potassium chloride. It is usually taken up by plant roots as the potassium ion, K+.

Occasionally, phosphorus and potassium may be expressed as elements P or K. Conversions from one form of P or K to another can be made by using the formula below:

% P	=	% P2O5 x .44
% P2O5	=	% P x 2.3
% K	=	% K2O x .83
% K2O	=	% K x 1.2

CHOOSING A FERTILIZER

In general, high analysis fertilizers that contain more of the major elements are also more economical than low analysis fertilizers. Solid granules are usually more economical than liquid for an equal amount of actual nutrient.

Many different fertilizers and fertilizer formulas are manufactured because different crops demand varying amounts of each nutrient for the best return on the investment. Some fertilizers are more effective than others on the various soil types and crops.

Many fertilizers can be combined to make up the desired applications. The sums of the nutrients will not always be exactly the rate needed but a variation of a few pounds per acre is not a great concern.

For example, to fertilize a crop at the rate of 120 pounds N, 62 pounds P2O5 and no K20, use several different combinations, such as:

Fertilizer	Pounds	N	Pounds P2O5
13-39-0	160	21	63
32-0-0	320	102	0
Total		123	62

Fertilizer	Pounds	N	P2O5
Anhydrous ammonia (82% N)	146	120	0
0-45-0	136	0	61
Total		120	61

BARNYARD MANURE

Barnyard manure is highly desirable on New Mexico soils because it increases their tilth. You may beneficially use 20 tons or more per acre. Manure usually does not supply enough readily available nutrients for maximum growth of short-season vegetable crops, and almost all crops will need supplemental fertilizer applications. The plant nutrient content of manure varies widely with the kind of animal, type of feed, and treatment and storage.

Manure does not decompose completely in one season. Apply it to the soil 6 to 12 weeks before planting. Plow or disc it into the soil as soon after applying as possible to reduce loss of nitrogen from volatilization.

The average ton of manure contains the following nutrients, in pounds:

Animal	N	P	K
Cattle	15	4	9
Sheep	22	6	22
Poultry	32	14	13

There may be problems associated with using manure. Some manures have a high salt content and can create problems if not leached adequately. Manure may also contain weed seeds that can introduce new weeds or increase the weed infestation.

HOW MUCH FERTILIZER?

Before buying the fertilizer for a farm, make a chart listing each field, the crop to be grown, fertility status of the field, and the amount of fertilizer required.

If fertilizer was applied to a field in the previous year and a normal crop was obtained, allow some carry-over nutrient credit. It is a good practice to leave some nutrients in the soil to maintain a good residual soil fertility level.

Because of the physical and chemical reactions of some fertilizers in the soil and various irrigation practices, all fertilizers do not always become available to the crop or are not taken up by the crop the year of application.

To determine how much of a fertilizer you need for a given rate, use the following formula:

Pounds of nutrient to be applies per acre x 100 ------------------------------------------------------------ % of nutrient in the back	=	Pounds of fertilizer required per acre

If the fertilizer rater per acre is:
	N	132 pounds
	P2O5	61 pounds
	K2O	0
And the fertilizers are:
	Ammmonium Nitrate	33% N
	Concentrated superphospate	45% P2O5
The amounts needed per acre are:
132 x 400 ---------- 33	=	400 pounds of ammonium nitrate
61 x 100 ---------- 45	=	136 pounds of concentrated superphospate

Suggested Application of Fertilizer Nutrients for Irrigated Crops

(Modify the rates of fertilizer applications suggested here by your own experience, local conditions, and management practices)

__________________________________________________________________________________

Crop	Pounds Per Acre			Remarks
Crop	N	P2O5	K2O	Remarks
Alfalfa
New Seeings	20	120	50	A starter of up to 20 pounds of N is
Established stands	0	120	50	Recommended for new seedings. Incorporate P205 for new seedings and top dress established stands in the spring.

Barley
Spring Winter	120	60	40	Apply P2O5 and K2O at planting time. Apply 1/2 N at planting time and 1/2 prior to jointing

Cabbage Broccoli Cauliflower	220	90	40	Apply all P2O5 and K2O at planting time. Apply 1/3 N at planting time, 1/3 at thinning and 1/3 after first fruit has set.

Carrots	120	60	30	Apply P2O5 and K2O at planting time. Apply 1/2 N at planting time and side-dress 1/2 after 6 weeks
Chile
Green	60	45	30	Apply P2O5 and K2O at planting time
Red	80	45	30	Apply 1/2 N at planting time and 1/2 after 8 weeks

Corn Field and Sweet	200	80	60	Apply P2O5 and K2O at planting time. Apply 1/2 N at planting time and side-dress 1/2 N at lay-by.

Cotton
Upland	120	60	40	Apply P2O5 and K2O at planting time.
Pima	100	60	40	Apply 1/2 N at planting time and 1/2 at first square
Cucumbers	100	80	30	Apply P2O5 and K2O at planting time. Apply 1/2 N at planting time and 1/2 when vining begins

Grapes	60	30	20	Apply P2O5 and K2O in the spring. Apply 1/2 N in spring and 1/2 6 weeks later

Green Beans	0-20	60	30	Apply at planting time.

Irrigated Pasutre
Grass	200	60	60	Apply P2O5 and K2O in the spring. Split N into 2-4 applications with the first in early spring
Grass Legume	160	75	60

Lettuce	200	100	60	Apply P2O5 and K20 at planting time. Apply 1/5 N at planting, 1/5 at thinning, 1/5 when first heads appear and the rest in 1 or 2 side-dressings during head development.

Oats	100	40	25	Apply P2O5 and K2O at planting time. Apply 1/2 N at planting and 1/2 prior to jointing

Onions
Grano (Fall Planted) Sweet Spanish	200	100	60	Apply P2O5 and K2O at planting time. On granos, apply 48 pounds of N at planting, 60 pounds in the spring when growth begins and the remainder in 3 equal parts with the last 30 days prior to harvest. For sweet Spanish apply 50 pounds N at planting time and 30 pounds at 21-day intervals beginning April 15.

Peanuts	20	60	30	Apply at or before planting.

Peas	20	60	30	Apply at planting time

Pinto Beans	20	45	25	Apply at planting time
Potatoes
Irish	200	180	150	Band all P2O5 and K2O at planting time. Band 1/2 N at planting time and 1/2 when plants are 6 inches tall.

Rye	120	60	40	Apply all P2O5 and K2O at planting time. Apply 1/2 N at planting and 1/2 just prior to jointing

Sorghum
Grain	150	90	60	Same as corn
Forage	200	85	60	Same as corn

Sorghum
Sudangrass	200	80	60	Apply all P2O5 and K2O at planting time. Apply 2 N at planting time and the remainder after cutting or grazing as needed

Sweet Potatoes	50	60	30	Apply all P2O5 and K2O when bedding. Apply 1/2 N at bedding and the rest when runners are 6 inches long.

Tomatoes
Hand (multiple)	160	150	120	Band all P2O5 and K2O below the row at planting. Apply 1/3 N at planting, 1/3 at first cluster set and 1/3 a month later.

Machine Harvest	120	150	120	Band all P2O5 and K2O at planting. Apply 1/2 N at planting and 1/2 at thinning.

Watermelon	80	80	60	Band all P2O5 and K2O before bedding. Band 1/2 N before bedding and 1/2 when vines begin to run.

Wheat
Winter Spring	100	45	25	Apply all P2O5 and K2O at planting time. Apply 1/2 N at planting time and 1/2 prior to jointing

Suggested Application of Fertilizer Nutrients for Orchards and Ornamentals

Established	Pounds per Tree per Year N	Remarks

Apples	1/4	Per inch of trunk diameter to a maximum of 5 lbs. N per tree
Pears	1/4	Split rate into two applications: One half before or at bud break, the other half in late May or early June. Do not fertilize after July 10.
Peaches	1/4
Peacans (bearing)	1/4
Shade or Ornamental Tree	1/4
Conifers	1/8	Nitrogen fertilization is not recommended in the first year of establishment

Chart for listing each field and determining fertilizer needs __________________________________________________________________________________

| Field	| Crop To Be Grown	| Fertility Status	| Fertilizer Required
|_______|_______________________|_______________________|_________________________|_
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|	|			|			|			  |
|_______|_______________________|_______________________|_________________________|_

This publication was funded in part by USDA-Federal Extension Service grant #89-EWQI-1-9171, Computeriztion of Soil Test Results and Fertilizer Recommendations.

New Mexico State University is an equal opportunity/affimative action employer and educator. NMSU and the U.S. Department of Agriculture cooperating.

Written: May 1990
Placed on Server: March 22, 1996