Pre-season / Early Season fertilizing strategies

With spring poised to … well … spring (at least after winter gets the last few kicks in), we start to turn our minds towards getting things ready for our soon-to-be-growing plants. If you have any perennial fruit plants/orchards, you might have already wrapped up the late winter pruning before things start to wake up again. Annual crop producers are starting to look to when the soil will thaw, dry up a bit and be warm enough for some initial preparation. Ok, maybe they’ll have to wait a few more days, since winter isn’t finished with us just yet.

It’s almost soil o’clock

Regardless of whether you are growing annual or perennial crops, or both, now is the time to start thinking about the soil and the nutrient load that will be sitting ready to feed the growing crops. It is important to consider replenishing some of the soil nutrients that were removed in the previous season’s crops. You should also consider which nutrients any previous crops might have contributed or left behind. You might have already added some organic matter as a part of your cropping cycle (e.g., cover crops, green manure) or maybe you added some composted manure or some other organic-based amendment in the cool weather of the fall. Maybe you haven’t.

Test first. Adjust afterwards.

While it might be possible to make a whole bunch of general fertilizer recommendations for various crops, there is a better and more effective way. It makes sense to start with an encouragement to gather as much information as possible. I think that testing your soil before you try and establish a perennial horticulture crop or start out in a new annual crop field is a given. I also think that testing your soils regularly (at least every couple of years, if not annually) helps you to keep a better eye on changes in the soil and pinpoint your nutrient management strategies and targets. This applies to both annual and perennial crop producers.

That may seem to be self-evident and obvious advice. If it is, then you can stop right here. However, one of the biggest struggles that I’ve had over the years, specifically with some perennial fruit orchards, is understanding why there isn’t more care and attention given to the long-term fertility requirements of the continuously growing and producing plants, or regular tracking of soil nutrient levels in annual crops.

Of course, some orchards monitor the soil nutrients regularly, and make regular deposits into the soil nutrient bank, recognizing that nutrients are being removed each year. But there are lots that don’t. They don’t make the connection between a good harvest of fruit for a few years, and then a steadily increasing decline in new growth, productivity, and plant health in the orchard.

I’m not suggesting that the only way to a highly productive crop is through dumping on lots of fertilizer. What I am suggesting is that there is tremendous value in gathering information and data to support whatever actions that you might or might not take. If you are going to make decisions based on assumptions, you can’t expect to have predictable results.

Nutrient testing can add expense and does take some time. It isn’t always easy to do. But I think that it will pay off, in the medium to long run. Look at it as something that should be done often enough that you can make confident management decisions when you need to.

Soooooo…, what if I don’t test…?

After all of that, even if you aren’t soil testing regularly, sticking with a conservative calendar approach to fertilizing some crops, especially perennial orchards, is better than doing nothing at all. In a pinch, you can rely on these general recommendations to keep things somewhat level. You can make observations of how the plants respond and tweak things from there. If you are running into specific issues, you should circle back to testing, otherwise, you are just guessing at probably causes and solutions.

For annual crops, like vegetables, a calendar is tougher, but there are general recommendations in the form of fertilizer ranges that you can use, if you want to. I look at them as more of a guideline of which crops are heavier feeders than others. You can also get clues as to which crops might need a bit more of one nutrient than another. When using these guidelines, I tend to stay closer to the bottom of the recommendation, unless you can make a case for how much nutrients might be there (e.g., which crops were grown previously, observed issues, etc.).

Timing of Fertilizer Applications

WHEN you apply fertilizers is almost as important as HOW MUCH you apply. This is because some nutrient sources take a bit of time to become available (e.g., composted manure and other organic matter), some products have to change forms, or some can be quickly leached and lost from the soil profile. Timing also affects when most of the nutrients might be available and used, or when they are most needed. Lots of our fertilizers are applied in the spring or the first part of the growing season.

Fruit Crops

For perennial fruit orchards (like Saskatoon berries and raspberries), timing is important, as you want to give them an early boost as they wake up and do a lot of their vegetative growing and setting a crop, then you want them to slowly slide into dormancy in the fall. Typically, we focus on applying nitrogen, but I like to suggest using something that is equal in nitrogen, phosphorus, and potassium, so you get a bit of each of the other nutrients at the same time.

For raspberries, you focus on one application of nitrogen as things wake up and as the snow melts, and then a second application in mid-May. The general recommended rates are to apply 20-40 pounds of actual nitrogen per acre (adjusted for banded applications) at each application date. For primocane-type raspberries, it can be a bit higher, 35-60 pounds of actual nitrogen per acre at each application (again, adjust for banded applications).

Like raspberries, Saskatoon berries also get two applications of nitrogen and phosphorus, the first in early to mid-May (as flower buds are starting to open), and the second at the end of June. Apply 15-25 pounds of nitrogen per acre and 10-15 pounds of phosphorus per acre (adjusted for banding) at each of the dates.

For crops like black currants (at least 2 years old – start of 3^rd year), you might apply up to 50 pounds of actual nitrogen per acre (adjusted for banding) at the end of April.

June-bearing strawberries are a bit different from the bush fruits, but similarly, part of the fertilization is focused on early season growth. To help established plants get going, apply 10-20 pounds of nitrogen per acre towards the end of April or in early May, as growth gets started. You’ll top things up after harvest is done, but that’s it for now. Day neutral strawberries have high nutrient needs and shallow roots, so they should receive 10-20 pounds of nitrogen per acre each month, probably split into weekly or bi-monthly applications.

Vegetable Crops

For vegetables, it really depends on what you are growing. Lots of the seasonal needs are applied as a granular product that is broadcast and incorporated in the early season before planting. I always suggest a shot of fertilizer (high phosphorus) be applied in a water-soluble form when any transplants are planted. You can always do a top-up application as a side dress, foliar, or top dress application later on, but most of your nutrient supplies will come from the pre-plant applications.

If you would like to see the different general (without soil test) nutrient application ranges for most of the main vegetable crops, have a look at Pages 142 to Pages 286 in the PDF version of the Commercial Vegetable Production on the Prairies manual (or Pages 133 to 277 in the print version). The general requirements are listed for each vegetable in their respective section.

https://www1.agric.gov.ab.ca/$Department/deptdocs.nsf/all/agdex15123/$FILE/250_13-1_web.pdf

Conclusions

There are lots of ways to supply the nutrients that the plants need to grow and thrive and be productive. Fertilizer comes in many forms. In the end, make sure that you have as much information as possible, to help you in your decision-making, then do what you have to so that the plants have what they need, when they need it.