“Crop nutrition is a staple, not an option. If you don’t want to fertilize the alfalfa, then you better be content with grasses and dandelions.”
Of all common farming practices, harvesting hay off the same field year after year is probably the hardest on the land.
The forage, be it alfalfa or grass, sucks up nutrients from the soil to build stalks and leaves, which are then baled up and carried off to parts unknown on the back of the haywagon, in most cases, never to return.
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It is akin to mining the soil.
Forage crops in the following years can’t get enough nutrients to support growth, and yields decline over time – like a bullet fired from a gun eventually falls to the earth.
Grain farmers have for many decades invested in fertilizer to replenish the soil in line with crop removal rates. The grain removed when annual crops are harvested represents about two-thirds of the total nitrogen and phosphorous uptake, and a quarter in terms of total potassium.
With forages, it’s more like 100 per cent of plant uptake. Alfalfa, for example, typically removes 15 pounds of phosphate, 60 pounds of potash, and five pounds of sulphur per ton. With grass hay, the removal rate is 10, 40, and four pounds of P, K, and S per ton, respectively.
So why do many farmers think they can keep removing nutrients in the form of hay without ever giving back?
“They might as well just put a ‘nutrients for sale sign’ up in the yard,” said John Heard, a Manitoba Agriculture soil fertility specialist.
“Crop nutrition is a staple, not an option. If you don’t want to fertilize the alfalfa, then you better be content with grasses and dandelions.”
DEPLETION CURVE
Fighting the nutrient depletion curve requires tough choices. Trying to farm on the cheap by forgoing nutrient replacement means a farmer must eventually reduce stocking rates and profit expectations, or “grow more land” to compensate for lower yields by haying more acres.
“If you don’t want to optimize production off that acre, then obviously you need more acres to get the same amount of forage,” Heard said.
“People need to recognize that if they don’t look after their forages well, then their productivity will drop off quickly. Nothing depletes the soil of nutrients quicker than forages.”
Of the nutrients in hay that goes in the front end of a cow, 80 per cent goes out the back in the form of feces and urine. Catching all of those nutrients and putting them back on the same acres, for example with bale or swath grazing, is the only way to fight nutrient depletion without spending money on fertilizer.
But even that practice has potential pitfalls, Heard added, because if the bales are placed too close together, the nutrients removed from hundreds of acres end up concentrated on a wintering site that may be only tens of acres, while the rest of the hayland where it came from remains starved.
SOIL TESTING
Soil testing is the only way of knowing for sure where the nutrient levels stand. Another useful indicator is the forage feed test. It can be used as a proxy for plant tissue analysis to pinpoint gross deficiencies in nutrients, but a soil test is the only way to know how much nutrients need to be applied to fix the problem.
Other indicators, such as ever-wider spaces between alfalfa plants that fill up with dandelions or grasses, or visual signs such as purple or yellowing leaves, are signs that the nutrients such as phosphorous, potassium or sulphur in the soil gas tank are on “E.”
Same with white spots on alfalfa leaves, which indicate a potassium deficiency.
But visual signals can’t always be trusted, because they may have arisen due to temporary factors such as cool soil conditions or drought.
“Those are the textbook indicators, but it isn’t very reliable. People will notice falling forage production long before they start seeing visual symptoms.”
MARSHY FIELDS
But marshy fields are often hayed year after year. How come they can get away with it?
That’s because water, as the first limiting factor in crop growth – well ahead of all the major macro-nutrients such as N, P, or K– tends to be more abundant in low-lying fields.
Also, the high organic matter content in swampy muck leaves the farmer with such a fat nutrient bank account that it may mineralize at a rate slow enough to provide decades of respectable hay crops, said Heard.
At any rate, fertilizing near wetlands is frowned upon by environmental officials.
Jane Thornton, a Manitoba Agriculture pasture and rangelands specialist, said that putting up hay
on swampy lands and taking whatever you get might be the best use for it, since it is probably unsuitable for any other use other than grazing.
“You can’t make a silk purse out of a sow’s ear,” she said. “Some of that land, if you were to try to improve it with tame forages, you’re really going to be fighting an uphill battle with inputs and efforts resulting in short-lived gains.”
She noted that there are many kinds of haymakers. Many beef producers don’t fertilize their hayfields except with the manure scooped out of their wintering pens.
FERTILIZER INVESTMENT
On the other hand, dairy and forage producers, who farm more intensively and aim for two or three cuts per season, are more willing to invest in fertilizer to maintain their production levels.
In a mixed legume-grass stand, as the alfalfa peters out, the brome grass will need nitrogen to sustain its growth. If it isn’t applied, less productive species such as Kentucky bluegrass will start creeping in as fertility levels fall. Soil testing at this point would show where things stand, she added.
“If it has completely changed to a whole bunch of forages that you don’t recognize, then maybe it’s time to rip the stand up,” said Thornton.
“Certainly, if people would put fertility on their alfalfa, it would probably last about twice as long.”
Whether it is cost-effective to fertilize forages depends on the cost, and whether the rain comes or not, she added, noting that in a dry year, the money spent might seem to have gone to waste.
Conversely, good rains can boost yields and mask nutrient deficiency problems, and lead some farmers to believe that fertilizing is unnecessary.
“You have to have fertility, because it’s a limiting factor, but on the Prairies, moisture is our most limiting factor,” said Thornton, noting that’s not something farmers in the Interlake want to hear right now.
Wintering animals on the hayfields may be the only way to keep up production without spending money on fertilizer.
But only on tame forages, she said. That’s because true native forage stands developed their own system for stabilizing fertility over the past 10,000 years, and messing with that fragile ecosystem can lead to irreparable harm.
“The plant community there has a way of taking care of itself without high amounts of nitrogen, phosphorous and potassium put on,” she said. “I would just use that only as summer pasture, and not upset the natural balance.”
Larry Fischer, a farm production adviser based in Gladstone, Manitoba said that with the price of hay at three to 3.5 cents per pound, spreading fertilizer could pay for itself.
“If they put $25 to $30 worth of fertilizer on and get an extra bale of hay, it’s like buying another bale of hay right on their farm,” he said.
