WO2011114221A1

WO2011114221A1 - Fertilizer composition

Info

Publication number: WO2011114221A1
Application number: PCT/IB2011/000571
Authority: WO
Inventors: Andrei Borisovich Rozanov; Ailsa Ghillainé HARDIE
Original assignee: Stellenbosch University
Priority date: 2010-03-19
Filing date: 2011-03-18
Publication date: 2011-09-22

Abstract

A pelletized fertilizer composition is provided which includes at least one active ingredient selected from urea, monoammonium phosphate (MAP), diammonium phosphate (DAP), potassium chloride and potassium sulphate. The composition is characterised in that it further includes charcoal onto which the at least one active ingredient is at least partially adsorbed, and it excludes potassium nitrate and ammonium nitrate.

Description

FERTILIZER COMPOSITION

FIELD OF THE INVENTION

This invention relates to a fertilizer composition, more specifically, but not exclusively, to a pelletized fertilizer composition.

BACKGROUND TO THE INVENTION

The continuous supply of nutrients to plants is essential in proper fertilization of plants for their growth. Nutrients necessary for the promotion of enhanced plant growth are divided into two categories. Macronutrients such as nitrogen, phosphorous and potassium are needed in larger quantities than micronutrients such as iron, manganese, copper, zinc, boron, chlorine and molybdenum. It is the function of fertilizer to provide these nutrients in suitable proportions.

It is well known for fertilizers to be pelletized in production. This manner of delivery to the soil proves to be easy to handle. When applied to the soil in this form, nutrients are released into the soil once the pellets become hydrated.

Conventional fertilizers may provide the necessary nutrients, but this is not the only essential factor to be considered. Leaching of nutrients is a common problem and results due to conventional fertilizers dissolution and transport of water-soluble compounds below the rooting depth of cultivated plants. This leads to excessive amounts of fertilizer being needed in order to deliver the needed nutrients to plants.

OBJECT OF THE INVENTION

It is an object of this invention to provide a fertilizer composition which will at least partially alleviate the above mentioned problems.

SUMMARY OF THE INVENTION In accordance with this invention there is provided a pelletized fertilizer composition which includes at least one active ingredient selected from urea, monoammonium phosphate (MAP), diammonium phosphate (DAP), potassium chloride and potassium sulphate, and is characterised in that it further includes charcoal onto which the at least one active ingredient is at least partially adsorbed, and which excludes potassium nitrate and ammonium nitrate.

Further features of the invention provide for the charcoal to have a particle size of less than 2mm; for the charcoal to be at least 10% by weight of the total composition; and for the pellets to be less than 5mm in diameter.

A fluid or plastic fertilizer mixture suitable for pelletizing comprising charcoal and one or more of urea, monoammonium phosphate (MAP), diammonium phosphate (DAP), potassium chloride and potassium sulphate, and which excludes potassium nitrate and ammonium nitrate.

A further feature of the invention provides for the moisture content of the mixture to be sufficient to permit adsorption of at least part of the fertilizer onto the charcoal. A method of controlling the release of a fertilizer to soil which includes adding charcoal particles to a fluid or plastic fertilizer mixture suitable for pelletizing and having a moisture content sufficient to permit adsorption of at least part of the fertilizer onto the charcoal, forming pellets from the mixture and administering the pellets to soil.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

A pelletized fertilizer composition is provided which, according to the invention, includes charcoal. To avoid potentially explosive mixtures from being formed by the addition of the charcoal, the mineral components of the fertilizer exclude nitrates, particularly ammonium nitrate and potassium nitrate, and are limited to one or more of the following active ingredients:

urea;

monoammonium phosphate (MAP);

diammonium phosphate (DAP);

potassium chloride; and

potassium sulphate.

Where urea is used as an active ingredient it is preferable to additionally use up to 10% lime and an organic compound as a stabiliser. Where K₂S0 is used up to 20% lime is preferably used as well. The addition of lime in these instances aims to neutralise the composition.

Incorporation of charcoal into the fertilizer composition requires it to be ground into small particles to be suitable for pelletizing. A very fine particle size is preferred, with the particles being at least smaller than 2mm in size, preferably smaller than 500pm.

Any suitable amount of charcoal can be included into the fertilizer composition. However, it is preferred that the composition include between 10% and 50% by weight of charcoal.

The incorporation of charcoal into fertilizer increases and improves nutrient retention within the fertilizer granule and ultimately enhances delivery of the nutrients to plants. The nutrients are adsorbed and absorbed onto the charcoal particle surface and then released to the plants through ion exchange. Charcoal is porous and thus has a large surface area available for adsorption. To facilitate adsorption of the fertilizer nutrients onto the charcoal, sufficient moisture must be added to the mixture before pelletizing and the mixture thoroughly combined. The ion exchange reactions between the charcoal and the nutrients control the availability of the nutrients to the plants. The sorption of nutrients onto the charcoal particles and the ion exchange reactions between the nutrients and the charcoal particles is also particularly useful in reducing loss of nutrients by leaching. The nutrients are thus available in the soil for longer periods of time and do not contribute to pollution of the ground and surface waters.

Additionally, organic and inorganic contaminants present in soil water are adsorbed and absorbed onto the surface of the charcoal particles. This contributes to providing a more favourable growing environment for plant growth.

Although any suitable fertilizer compositions can be used, it is envisaged that the addition of charcoal will be particularly effective with fertilizers containing ammonia and potassium due to the availability of both positive and negative charges on the surface of charcoal particles.

The following examples illustrate two methods of preparation of fertilizer compositions according to the invention. These are by way of example only, and it is to be understood that the invention is not limited to the compositions or methods described.

EXAMPLE 1

An organic, dehydrated fertilizer composition is prepared with the three essential macronutrients, nitrogen, phosphorous, and potassium. A composition incorporating these macronutrients in a ratio of 15:45:10 is formulated by combining 15 parts cottonseed meal, with 19 parts bone meal and 8 parts kelp meal. As a source of calcium and magnesium, 4 parts dolomite lime is added.

Charcoal is ground and sieved until particles with a size range of less than 0.5mm are obtained. This is incorporated as a powder into a fertilizer mixture in an amount totalling 25% by weight of the overall fertilizer composition. The fertilizer mixture has a high moisture content to make it suitably plastic for use with a drum granulator (or pelletiser). After thorough mixing of the charcoal with the other components, the mixture is then dehydrated as it is fed into the granulator to form pellets of organic fertilizer.

EXAMPLE 2 A liquid fertilizer composition is prepared using aqueous ammonium chloride in conventional fashion. Potassium sulphate is added as a potassium source. An amount of charcoal corresponding to about 50% by weight of the ammonium chloride used is crushed and sieved to obtain small particles with a size range of between 10 to 50 microns. This is then added to the ammonium chloride as a suspension in water. Finally, a thickening agent, such as an anionic polyacrylamide, is also added to the composition for pellet stabilization.

This mixture is fed into a spray-drying tower in which suitably sized pellets are formed.

The fertilizer compositions provided in the above examples are relatively easy to manufacture as conventional methods of fertilizer preparation are used and do not need to be materially modified to include the use of charcoal. Manufacture of the fertilizer pellets of the invention requires only the addition of the charcoal into well- known methods of both natural and synthetic fertilizer preparation. Also, charcoal is relatively easy to source and is fairly inexpensive.

The fertilizer pellets of the invention are, however, highly effective in controlling the release of nutrients to plants and preventing unnecessary leaching of the nutrients. This in turn results in less fertilizer being required than is normally the case which in turn limits the costs and also limits the amount of nutrients available for leaching.

EXPERIMENTAL RESULTS

99:1 Charcoal/fertilizer mix applied at 1t/ha A fully randomized pot trial was set up in a green-house. Wheat was grown in 6-kg pots filled with sand (pH _(water) = 5.2, pH _(κα) = 4.1 ; No pH adjustment was made).

Experimental Layout

Ten pre-treated wheat seeds were sown to a depth of approximately 20 mm in each pot. After germination, the seedlings were thinned, and the healthiest 4 plants were retained in each pot. Pots were irrigated weekly to field capacity. The pots were arranged in a randomized complete block design. The broad spectrum fertilizer (Table 1) used was added as a solution as a split application of 70% at planting, 30% after 4 weeks of growth, and an additional 30% 4 weeks thereafter due to visible wheat leaf deficiencies. Above and below-ground biomass production was measured after 12 weeks upon destructive harvesting.

Table 1 : Composition of broad spectrum fertilizer

Macronutrients kg ha ¹ Micronutrients g ha

N 130 Fe 865

P 50 Mn 138

K 75 B 138

Ca 40 Zn 29

Mg 13 Cu 12

S 43 Mo 6

Charcoal was added in powder form to the soil at the ratio of 99:1 to fertilizer mix resulting in 1% fertilizer concentration the mix was applied at the rate of 1 t/ha.

Three treatments were considered:

1. F0 - Unfertilized sand.

2. F1 - Soil + complete fertilizer supplement

3. F1 C - Soil + complete fertilizer supplement + charcoal

As expected, the addition of fertilizer yielded significantly higher biomass production. Use of 99:1 charcoal fertilizer mix resulted 35% increase in total biomass production over pure fertilizer of which 22% was above-ground, and 65% below-ground as shown in Table 2. Table 2: Results of fully randomized pot trial to test the effect of 99:1 charcoal/fertilizer mix on biomass production of wheat plants after 12 weeks of growth in a greenhouse

Total shoot biomass

Treatment Total root biomass (g) Total biomass (g)

(g/pot)

AVG STD DEV AVG STD DEV

FO 1.29 0.12 1.21 0.27 2.49

F1 18.91 2.83 9.82 1.86 28.73

F1 C 23.07 0.19 15.88 2.1 1 38.96

% change 22.05 61.65 35.59

Single factor ANOVA analysis (Table 3) shows a significant difference at Alpha=0.01 between fertilizer and fertilizer+charcoal applications with increases in above ground biomass production reported in Table 2.

Table 3: Results of fully randomized pot trial to test the effect of 99:1 charcoal/fertilizer mix on biomass production of wheat plants after 12 weeks of growth in a greenhouse

Anova: Single Factor

SUMMARY

Groups Count Sum Average Variance

F1 4 75.625 18.90625 8.022988

F1 C 4 92.298 23.0745 0.037982

ANOVA

Source of Variation SS df MS F P-value F crit

Between Groups 34.74862 1 34.74862 8.621448 0.026075 13.74502

Within Groups 24.18291 6 4.030485

Total 58.93153 7

The observed difference was significant at Alpha= 0.01 with P=0.026.

Application of the above fertilizer mix has also resulted in significantly reduced variation between replications in F1 C treatment shown in Table 4. Charcoakfertilizer mixed resulted in much smaller variation in above-ground biomass production between treatments yielding more stable results. Table 4: F-Test Two-Sample for Variances

F1 F1C

Mean 18.90625 23.0745

Variance 8.022988 0.037982

Observations 4 4

df 3 3

F 211.2332

P(F<=f) one-tail 0.000548

F Critical one-tail 9.276628

It will be appreciated that many other embodiments of pelletized fertilizer compositions exist which fall within the scope of the invention, particularly regarding the preparation and formulation of the fertilizer. It will also be appreciated that any suitable amount and particle size of charcoal can be used. Also, any suitable pelletizing process can be used.

Claims

1. A pelletized fertilizer composition which includes at least one active ingredient selected from urea, monoammonium phosphate (MAP), diammonium phosphate (DAP), potassium chloride and potassium sulphate, and is characterised in that it further includes charcoal onto which the at least one active ingredient is at least partially adsorbed, and which excludes potassium nitrate and ammonium nitrate.

2. A pelletized fertilizer composition as claimed in claim 1 wherein the charcoal has a particle size of less than 2mm.

3. A pelletized fertilizer composition as claimed in claim 1 or claim 2 wherein the charcoal is at least 10% by weight of the total composition.

4. A pelletized fertilizer composition as claimed in any one of the preceding claims wherein the pellets are less than 5mm in diameter.

5. A pelletized fertilizer composition as claimed in any one of the preceding claims having the following composition:

6. A fluid or plastic fertilizer mixture suitable for pelletizing comprising charcoal and at least one active ingredient selected from urea, monoammonium phosphate (MAP), diammonium phosphate (DAP), potassium chloride and potassium sulphate, and which excludes potassium nitrate and ammonium nitrate.

A mixture as claimed in claim 6 having a moisture content sufficient to permit adsorption of at least part of the at least one active ingredient onto the charcoal.

A method of controlling the release of a fertilizer to soil which includes adding charcoal particles to a fluid or plastic fertilizer mixture suitable for pelletizing and having a moisture content sufficient to permit adsorption of at least part of the fertilizer onto the charcoal, forming pellets from the mixture and administering the pellets to soil.