Fertilizer
If you've found that your pasture just isn't as green and healthy as you'd like then perhaps it's time to fertilize.
Chemical fertilizers are certainly an option to help revitalize your pasture. The rain and minerals taken away by agriculture and animal production may eventually diminish the lands ability to produce grass and other plants needed to feed your flock.
Chemical fertilizers typically contain three components; Nitrogen, Phosphorus, and Potassium.
| | Plant & Sheep Benefits |
| Nitrogen | Necessary for Amino Acid Production - Amino Acids combine to form protiens used in building the bulk weight of the plant. To build fat sheep you might use high protien feeds but with plants you would instead use greater amounts of nitrogen. |
| Phosphorus | Needed for ATP (Adenosine-5'-triphosphate) - This wicked sounding name is a chemical that all life uses to transfer energy and control metabolic rates. Without phosphorus the plant's ability to grow is limited and no matter how much sun the plant gets it won't be able to store that energy for its own growth. Our sheep need phosphorus for the same reason which is reason enough to apply appropriate amounts of usable phosphorus to the pasture soil. |
| Potassium | Important component needed for Photosynthesis, Osmotic cell pressure regulation, and the activation of enzyme systems -- Potassium deficiency will slow plant growth, delay maturity and seeding, and retard the addition of bulk weight to the plant. We see much the same thing in sheep as deficient amounts of potassium can readily cause heat stress as water is not retained well and the sheep's energy begins to diminish. |
Why not feed fertilizer to the sheep?
Plants are the powerhouse of all life. They can take the basic building blocks, sometimes as simple as the raw elements, and using the power of the sun change them into other chemical forms usable by animals. Without plants at the base of the food chain then all life would die off. While the nutrients are commonly needed by both plants and animals, animals can only use certain types chemical forms.
What are the "Numbers" on the fertilizer bags?
The numbers used on the bags of commercial fertilizers tell you what's in the fertilizer. The first number is % Nitrogen(N), the second % Phophorus(P), and the third is % Potassium(K). Hence, a bag of 24-2-11 would be 24% Nitrogen, 2% Phophorus, and 11% Potassium by weight. The balance of the weight (in this case 63%) is typically stabilizers and other means of conveying the nutrients to the plants (called "Ballast"). If it weren't for ballast then it would be extremely difficult to spread the fertilizer evenly and even minute amounts of spillage would burn your lawn or crop.
The numbers on the bag don't always convey the dollar value you get from the bag. There are several ways to look at calculating "Value" of the fertilizer. Farmers, for example, will use rather complicated calculations and spreadsheets that take into account year end harvest yields and the cost of the fertilizer used on the crop. But since we're simply trying to grow better grass then probably the easiest and simplest method of calculating value is based on cost per pound Nitrogen ($/Lb N).
As an example I found and listed several fertilizers WITHOUT any kind of weed control (Which you should never use on your pasture). Calculating the cost per pound nitrogen for each makes comparing the value very easy and obvious.
| | Ace Brand | Scotts
Turf Builder | America's
Groundskeeper
| Schultz Turf Exp. |
| Purchase Price | $24.99 | $17.59 | $9.99 | $32.37 |
| Weight (lbs) | 45 | 20 | 50 | 54 |
Coverage (sq.ft)
(Calculated Assuming 1 Lb N per 1000 sq ft. This is NOT the Mnfg. recomendations for coverage) | 13,500 | 7,000 | 12,000 | 16,200 |
| % Nitrogen (N) | 30 | 35 | 24 | 30 |
$/1000 sq ft
(Adjusted for 1 Lb N per 1000 sq ft) | $1.85 | $2.51 | $0.83 | $2.00 |
| $ / Lb Nitrogen | $1.85 | $2.51 | $0.83 | $2.00 |
From the above table and knowing a little about their advertizing, you can see that name brand name makes outstanding and sometimes outrageous claims about their product but they are simply advising you to put more nitrogen per acre than the plain wrap brands (Do the math based on their recommended coverages and you'll arive at somewhere between 20-40% more Nitrogen being added to the soil. No wonder the grass is greener !).
For your needs the most useful information will come from the calculated product "content"; typically lbs nitrogen or $/lb N. On a per-pound Nitrogen(N) basis you're probably better off getting your fertilizer from a bargain brand then you would from a "Name" brand fertilizer because they have no advertising overhead added into their product costs. You may even find something on sale or clearance. By the way, there is no expiration on fertilizer so long as it stays dry so finding something off-season in a very old and faded wrapper is just as good as a new bag just released for the new growing season..
I keep my eyes open for deals like America's Groundskeeper (My latest great 'deal') as shown in the table above. I snatched several bags for my pasture this year as it was a no brainer for cost. For our needs the brands names have no added benefits when you consider that we're basically fertilizing what most people call weeds. The added perk from this particular fertilizer I found was that it also contained potassium (See picture) which has been heavily leached out over the years in my climate.
One additional thing that some people might want to look at when examining fertilizer content are a few of the heavy metals that might be in them. You can look up many of the commercial fertilizers using WSDA Fertilizer Contents.
You can see from this website link that there are many more components in fertilizers then you might expected such as Arsenic(As), Lead(Pb), Cadmium(Cd), Chromium(Cr), Nickel(Ni), and even Mercury (Hg). However the amounts listed are VERY low (ppm = milligrams per kilogram in solids) in most cases and are heavily diluted once applied, especially if they are spread on a pasture broadly. Soils tend to bind up these elements and they are not taken up by the plants or sheep.
One way I express this idea to people is to think in terms of paper clips. If a fertilizer were to contain 45 ppm lead (A very high number for lead) that would be the equivalent of the weight of a single paperclip (about 1 gram) in an entire 50 lb bag of fertilizer, which will likely be spread over 15,000 sq feet (A typical lead bullet might weigh several grams yet we don't worry about them). This is a very small amount and would in no way affect the livestock, plants, or water runoff. Investigating most of these fertilizers you'll see the amounts of these contaminants are normally far lower than I used in this example. However, if you're raising organic meets, then probably none of this would be acceptable even though it makes no difference to human or livestock health.