METHYLENE UREA - A CONTROLLED RELEASENITROGEN SOURCE FOR TURFGRASSES

George R. McVeySenior Technical Associate0. M. Scott & Sons Company

Marysville, Ohio 43040

The development of nitrogen products derived from condensing urea withformaldehyde represented a significant advance in nitrogen fertilizer technology.This technology provided the basis for developing nitrogen containing fertilizerproducts with some properties similar to natural organic nitrogen sources. Thesesimilarities include (1) a controlled release of nitrogen and (2) a low burnpotential. Additional beneficial properties over natural organics nitrogensources provided by urea-formaldehyde condensation products include (1) highnitrogen analysis (38% vs. less than 10% nitrogen), (2) excellent consistency,(3) improved flexibility in adjusting nitrogen release characteristics, (4)odorless, and (5) economical.

According to a report in Marketing Research Report on Controlled ReleaseFertilizers by Jeanie H. Ayers, Chemical Economics Handbook, Menlo Park,California (Oct. 1978), nitrogen derived from urea formaldehyde condensationproducts accounted for 90% of all the controlled release nitrogen consumed inthe United States.

While the generic name "ureaform" and ureaformaldehyde has been used for anumber of years to describe the condensation products of urea and formaldehyde,it has been suggested (0'Donnell, personal communication, 1976) that methyleneurea (MU) would be technically more accurate. This name, methylene urea, shallbe used in the discussion to follow.

The early pioneering research carried out at the USDA and reported in 1946by Yee and Love (Proc. Soil Science Soc. Amer., 11, 389) showed that a nitrogenproduct with controlled availability could be made by condensing urea withformaldehyde under specific reaction conditions. Following this initial research,two distinct categories of methylene urea products were commercialized. Thesetwo categories differed primarily in their solubility characteristics as affectedby the distribution of the mixture of methylene urea polymers in the finalproduct plus the level of un-reacted urea.Manufacturing

Production of methylene urea requires exact control of temperature, pH,reaction time and reaction components. The release characteristics can becontrolled by modifying the reaction variables. As shown in Table 1, there are6 basic components required for production of methylene urea. Urea and formalde-hyde are the major components while sulfuric acid, sodium hydroxide and surfact-ant are only required in molecular quantities.

In the reaction process, urea reacts with formaldehyde to produce mono-methyl ol urea which further reacts with urea to produce methylene urea varyingin chain length (2 to 5 urea molecules, or possibly even higher, attachedtogether with methylene groups). (Table 2).

The manufacturing of these products differs relative to the ratio of ureato formaldehyde used and the reaction conditions. Dr. John Hays on the panelwill discuss the products common to Category 1 while my discussion will be onthe methylene urea products of a second major group, Category 2 (see Table 3).

60

Chemical PropertiesAs a basis to give you some background on the two major categories of

methylene urea products, typical chemical characteristics are shown in Table 3.A further breakdown on the distribution of nitrogen components within thesolubility fractions will also help to characterize differences in these twocategories (see Table 4).

The nitrogen release characteristics of methylene urea can be controlledby the method of manufacturing selected. Analytically the release characteris-tics are classified by the solubility of this product in water varying intemperature. Two temperatures are selected (1) room temperature (22°C) and (2)boiling water (100°C). Based on the solubility at these two temperatures, thebiological activity can be predicted. As shown in Figure 1 as the percent ofthe cold water insoluble nitrogen which is soluble in hot water decreases (NAI),the nitrification rate (conversion of methylene urea to nitrates) decreases.The nitrification rate is dramatically reduced as compared to ammonium sulfateand urea. This rate can be reduced to a point which is relatively biologicallyinactive.

One of the primary benefits of methylene urea is attributed to its low saltindex. As shown in Table 5, the low salt index at equal rates of material isdramatically reduced as compared to conventional fast release N sources. Thesedifferences are even more dramatic when compared on an equal nitrogen basis.Since the salt index is a measure of burn potential, it is obvious that on anequal weight or equal N basis, methylene urea would have a much lower burnpotential as compared to soluble N sources.

The slow release characteristics of methylene urea are also reflected inthe rate of conversion to ammoniacal and nitrate nitrogen in the soil. As shownin Figure 2 and 3, the ammoniacal nitrogen level in the soil solution is up to 4times higher when treated with urea as compared to the methylene urea. After 6weeks, the ammoniacal nitrogen level is essentially zero regardless of nitrogensource. In contrast, the nitrate nitrogen level dramatically increases as theammoniacal nitrogen level decreases. This was only evident if the nitrogensource was methylene urea (Figure 3). The nitrate nitrogen level continues ata high level for 120 days (50-100 ppm) if the soil was treated with methyleneurea. In contrast, soil treated with urea newer had a nitrate level greaterthan 30 ppm. Urea readily leaches from the media before conversion of urea tonitrates can be realized.

Biological PropertiesControlled release nitrogen sources are often characterized by improved

safety, increased residual, a more uniform growth pattern and less total clippingremoval as compared to turf treated with soluble nitrogen sources.

As shown in Table 6 as the percent cold water insoluble nitrogen increases,the degree of injury decreases. These differences are more dramatic when thefertilizer is applied to wet turf, however, still are apparent on dry turf. At acold water insoluble nitrogen (CWIN) of 42%, injury was not objectional at allrates (1-4 1b. N/M) or methods of application (wet vs. dry foliage). In contrast,complete formulations containing only 2% CWIN caused extreme foliar injury whenapplied to wet foliage using only 1 lb. of N/1000 sq ft. under the conditions ofthis study (applied in late August under high temperature conditions).

When comparing methylene urea from Category 1 to Category 2 relative to turfresponse, a substantial difference in turf color was noted. As shown in Table 7,the spring greening response from a late fall fertilization was very slow whenturf was treated with ureaform (Category 1) but was dramatically increased when

61

treated with methylene urea (Category 2). In this same experiment, the nitrogensource IBDU was also included. Initial response was comparable to ureaform whilethe residual of methylene urea and ureaform was longer than for IBDU (see Table 7).

Spring application of IBDU and methylene urea (Category 2) were compared(see Table 8). In this study, initial greening was very slow when treated withIBDU even though rates of 2 lbs. of nitrogen per 1000 sq. ft. were applied. Incontrast, turf treated with methylene urea exhibited a rapid spring greeningresponse. The residual characteristics of these products were similar.

The residual of the methylene urea (Category 2) was compared to urea. Asshown in Figure 4, the initial surge of growth was reduced from 1.9 grams forturf treated with urea down to 1.1 grams when the turf was treated with methyleneurea (42% reduction in fresh weight). The reduction in initial surge growth isreflected in the residual. These differences are not dramatic from only oneapplication, however. When repeat applications of methylene urea from Category 2were used, the residual characteristics became more apparent as shown in Figure 5.In this study, the fertilizer program was discontinued in the fall of the 2ndyear. Clipping fresh weights in the spring of the 3rd year dramatically reflectedthe residual characteristics when methylene urea containing 42% CWIN was comparedto a product containing 2% CWIN. The color of the turf treated with the controlledrelease nitrogen source (23-7-7 42% CWIN) was comparable to turf treated with thefast release N source (10-6-4 2% CWIN) in 27 out of 32 observations over a 2 1/2year period (see Figure 6).

Turf growth is another measure of the controlled release properties ofmethylene urea. The total fresh weight of clippings can be substantially reducedwhen turf is treated with methylene urea as compared to urea. As shown in Table 9,clippings removed over a 6 week period was reduced by one third when Kentuckybluegrass was treated with methylene urea as compared to urea. The lower clippingremoval is reflected in less tendency for scalping because of delayed mowing, areduction in mowing frequency and less labor for collecting and removing clippings.

In another experiment, we compared two kinds of methylene urea sources fromCategory 2 (see Table 10). Two products varying in percent CWIN were applied inearly October to Kentucky bluegrass. While it is often reported that methyleneurea products will not provide a good color and growth response under cool soilconditions, these results are to the contrary. The product containing 36% CWINinduced better turf color than products containing 50% CWIN suggesting greeningresponse is associated with the percent CWIN in the product. This again illus-trates the flexibility in formulating methylene urea products to meet the biolog-ical demands of turf.Summary

1) The properties of two groups of methylene urea, other slow releasenitrogen sources and soluble nitrogen sources vary widely relative tochemical and biological properties.

2) Varying the water soluble and insoluble characteristics of methyleneurea of Category 2 (see Table 4) provides substantial flexibility inmanufacturing products to meet varied use conditions for turfgrass.

3) The methylene urea nitrogen sources offer advantages relative to turftolerance, lesser growth response, increased nitrogen efficiency andreduction in pollution potential as compared to soluble nitrogen sources.

This technology has additional benefits which have been overlooked over theyears. The pollution potential of nitrogen can be reduced by this technology.This has created a renewed interest in methylene urea in many areas of agriculture.

62

Table 1. Materials Used in the Production of Methylene Ureas

Compound

Urea

UFC (60% Urea)

Sulfuric Acid

Sodium Hydroxide

Water

Surfactant

Function

Nitrogen Source

Formaldehyde Source (25%)

Catalyst

Stabilizer

Diluent

Foaming Agent

RelativeProportions

1000

480

10

1

133

63

Table 2. Symbolic Representation of Methylene Urea CondensationReaction

Monomethylol Urea

( U )

Monomethylol Urea Methylene Diurea

u) +#( u )

Methylene Diurea Dimethylene Triurea

CDimethylene Triurea

U X M X U

Trimethylene Tetraurea

Symbols ( U ) (Urea), <F> (UFC), [T] (Sulfuric Acid)

(Sodium hydroxide), (H) (Water), A (Surfactant)

(Methylene Group)

64

Table 3 .Nitrogen Characteristics of Typical Methylene Urea Products CommerciallyAvailable.

Nitrogen Characteristics

Total Nitrogen %

Nitrogen Active Index (NAI)

Cold Water Soluble Nitrogen (CWSN)

Cold Water Insoluble Nitrogen (CWIN)

Category 1-' Category 2 - 'Percent

38

33

25

75

38

60

64

36

1/ Ureaform (Hercules Incorporated and E. I . duPont deNemours & Company, Inc. )

2/ Methylene ureas (O..M. Scott & Sons)

65

Table 4.

Approximate Distribution of Methylene Urea Fractions and Urea inCommercially Available Products.

Nitrogen Characteristics

Total Nitrogen

Nitrogen Active Index (NAI)

Cold Water Soluble Nitrogen

Urea

Methylene Diurea

Dimethylene Triurea

Cold Water Insoluble Nitrogen

Trimethylene Tetraurea

Pentamethylene Hexaurea

Category

38

33

25

75

8

7

10

21

54

1/ 2/1 - Category 2 -Percent

38

60

64

36

28

27

9

22

14

1/ Ureaform (Hercules Incorporated and E. I. duPont de Nemours &Company Inc.)

2/ Msthylene urea (O. M. Scott & Sons)

66

Table 5. Salt Index of Various Nitrogen Sources.

Nitrogen Source

Sodium Nitrate

Ammonium Nitrate

Urea

Ammonium Sulfate

Methylene Urea

% N

16

33

46

21

38

Salt IndexEqual Weights

100

105

75

69

4

1/2/

Equal N Levels

6.25

3.18

1.63

3.29

0.11

1/ Concentration of ions in the soil solution based on sodium nitrateat 100.

2/ Nitrogen is mixed with air dried soil which is brought to 75% offield capacity and stored for 5 days at 5° C.

67

Table 6. Percent Injury of Merion Kentucky Bluegrass as Affected bySoluble and Partially Soluble Nitrogen Sources Applied toWet or Dry Foliage!/.

2/ 3/Percent Injury— —

Analysis

10-6-4

16-8-8

23-7-7

% CWIN

2

38

42

Wet

70

15

0

1

Dry

0

0

0

Lbs2N/1000 Sq Feet

LFoliage Condition When

Wet

70

35

5

Dry

15

0

5

Wet

100

80

0

XAppliedDry

20

5

5

Average

Wet

80

43

2

Dry

12

2

3

1/ Waddington, Duich and Moberg, Lawn Fertilizer Test Progress Report296, June 1969. The Pennsylvania State University, University Park,Perm.

2/ Recorded 2 days after application (August 26, 1966).

3/ Temp. 73, 84, 90°F max. and 52, 59 and 53°F min. on 0, 1 and 2 daysafter treating, respectively. Relative humidity 39-491.

68

Table 7.

Initial and Residual Color Response of Kentucky Bluegrass as Affectedby Various Nitrogen Sources Applied in Late Fall (11/22/77).

Initial Response Residual ResponseColor (10>l)

% # Date of ObservationN Source Category CWIN N/M 12/1 477 4/19 5/10

Methylene Urea 2 38 0.9 6.0 5.0* 5.0* 5.7*

Ureaform 1 75 0.9 6.0 3.7 4.0 6.0*

IBDU (coarse) - 78 0.0 6.0 3.5 4.0 4.3*

Control - - 0 6.0 2.5 2.7 2.0

LSD .05 NS 1.6 1.3 1.5

* Significant improvement in color as compared to the check (no fertilizer)

BC 800.2-C-77-326-1

69

Table 8.

Initial and Residual Response of Kentucky Bluegrass as Affected by VariousNitrogen Sources Applied in Mid Spring (5-18-77).

Initial Response Residual Response

N Source

Methylene Urea

IBDU (coarse)

Control

% CWIN

38

78

#N/M .

2.0

2.0

0

5/31

10.0

4.3

2.3

Color 10 > 1Date of Observation

6/14

9.3

6.3

3.7

7/29

8.3

7.0

4.3

70

Table 9 . Fresh Weight of Kentucky Bluegrass Clippings Removed from a10,000 Sq. Ft. Area as Affected by Methylene Urea or Urea.

Weeks after Application

Product

Methylene Urea

Urea

Lbs

0

0

. N/M

.9

.9

1

1908

2872

2Lbs. of

1372

2241

4Clipping/10

2120

2840

6,000

64

84

TotalSq. Ft.

5464

8037

%

681/

100

1/ Approximately 1/3 less clippings when turf is treated with methyleneurea as compared to urea.

71

Table 10.Fall Greening Response of Kentucky Bluegrass as Affected by TwoMethylene Urea Sources (Category 2) Applied in Ear ly October(10 /2 /78 ) .

N Source

Methylene

Methylene

Control

Urea

Urea

% CWIN

36%

50%

_

# N/M

0.9

0.9

0

10/17

8.0

7.3

3.0

ColorDate of10/27

9.0

8.0

4.7

(10 >1)Observation11/14

7.8

6.3

3.0

11/20

6.7

5.3

2.0

Average

7.9

6.7

3.2

BC 800.2 62-78-275-2

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Mi i^ei^ht d£ Kentucky ^luegrass :as A6Eedteed fey tfeea sm& fetfoyie?te Urea Applied a t

Residual Response

j

en

N/10010 Sq. |Ft.

ControlUreaMethylene Urea

initial Response

FreshWeight(gms)

FreshWeight(grns)

Weeks' AfterTreating

Weeks AfterTreating

BC 151-78-101-6

Figure 5. Clipping Fresh Weight of Poa pratensis Treated with a 2% CWIN Source (10-6-4)54* Expressed as Differences from Turf Treated with a 42% CWIN Source (23-7-7)1/

-3010 20 30 40

5/25/65 Cutting NumberA Fertilizer Applied at 1 lbs nitrogen/1000 sq. ft.* Significantly different from 23-7-7 at the 5% level1/Waddington, Duich § Moberg, Lawn Fertilizer Test Progress jleportThe Pennsylvania State University, University Park, Penn.

!0 X 10 TO THE IV:HKEUrFEL & ESiLR CO.

Figure 6. Color of Poa pratensis Treated with a 2% CWIN Source (10-6-4) Expressed^ treated with 42% CWIN Source (23-7-7) 1/

00

20 30 40 5f)5 / 2 5 / 6 5 •;••:•• , I C u t t i n g N u m b e r • ••

A Fertilizer applied at 1 lb N/1000 sq. ft.* Significantly different from 23-7-7 at the 5% level : !1/ Waddington, Duich § Moberg, Lawn Fertilizer Test, Progress Report 296, June 1969v

The Pennsylvania State University, University Park, Penn..._. J