Growing Gilchrist Vol. 3: Get Your Garden Right!
Get Your Garden Right
Have you been thinking about planting a spring garden or are doing it now? Whether you have a garden every year or this is your first time, getting off on the right start is the key to success. This starts by considering what your garden objective is. Do you want to produce enough for canning or feeding all the neighbors? Or do you want something easy to care for to supplement you and your family’s daily meals?
In either case there are three things to think about with your garden this year. 1. The plants you select. 2. How are you going to feed those plants? and 3. How much or how little water do they need?
If you can think about these things from the start you should get your garden right this spring.
Where to Start
It may sound like a broken record from the extension office but the best place to start whether its a garden, hay field, or watermelon field is with a soil test. This can come from the UF/IFAS Soil Testing Lab or a private lab, but in either case this lets us know what we are working with and will help us to make sure we don’t get any surprises once we plant our gardens.
Fertilizer is expensive, so if we can keep from using more than we need everyone benefits. Also not using more than the plant needs keeps us from damaging or killing the plant. A soil test will tell us what we may already have in our soil that we don’t need to supplement to have a successful garden.
Any soil test will test for soil macro and micro-nutrients. If you aren’t familiar macro-nutrients they are the big three, Nitrogen, Phosphorus, and Potassium or more commonly recognized as N-P-K. These three numbers are on every bag of fertilizer and are usually how people select a fertilizer. For example, a bag of 10-10-10 contains 10 lbs. of N, P and K in every 100 lbs. of fertilizer while a bag of 16-4-8 contains 16 lbs. of Nitrogen, 4 lbs. of Phosphorus and 8 lbs. of Potassium. You soil test will tell you whether your soil have high, medium or low values phosphorus and potassium and will provide a general recommendation for how much of each of these elements you need to amend your soil with. You may have noticed I haven’t mentioned nitrogen on your soil test. Nitrogen is a topic with its own section in this newsletter which I will cover later.
A soil test will also measure and make recommendations on the 7 micro-nutrients that plants needs to survive. These nutrients are required in much lower quantities than the big three macro-nutrients. Most fertilizers will list the ones included on the analysis tag so you can pick a fertilizer that contains those your soil tests indicates your soil is deficient in. If you use a fertilizer that includes micro-nutrients you can typically address any deficiency with our causing any problems. However, some micro-nutrients can cause toxicity at too high of levels so if you are concerned about apply too much or your soils are high in one or more of these nutrients then that is a great opportunity to talk to the extension office and come up with a specific plan how to deal with the problem.
A soil test will also tell us what the pH of our soil it which is one of the most important soil characteristics for a garden.
Soil pH tells us a few things about our garden. First, it tells us which plants or varieties to select to be successful. For instance, a blue berries require low pH soils (i.e. <6.5) so planting them in your garden with a high soil pH (<7.5) probably isn’t a good idea. So doing your homework on the plants and varieties you want to plant this year and knowing your soil pH from your soil test can spare you lots of headache trying to grow plants on soils they don’t belong.
However, don’t let your soil pH crush your garden dreams. Knowing your soil pH also mean you can make soil amendments to make it more suitable for the plants or varieties you want to plant. For instance, adding lime to a soil with a low pH will help bring that pH up while adding elemental sulfur can help bring a high pH soil down to a lower pH.
The Big N: Nitrogen
Nitrogen is the most important nutrient to plants grown on Florida soils. When you receive a soil test result it almost always will make a nitrogen recommendation for the crop you specified. This is not a measure of nitrogen in your soil because there is not a test for soil nitrogen. Instead this is an estimate based on years of research on the crop you specified to determine what is the optimal amount of nitrogen. This estimate is made based on plant tissue tests and yields of the crop in concern.
Here are the UF/IFAS recommend rates of nitrogen for some of your more common vegetable garden crops.
|Crops||Target pH||N (lb/acre)|
|Tomato, pepper, potato, celery, sweet corn, crisphead lettuce, endive, escarole, romaine lettuce, and eggplant||6.0 (potato) and 6.5||200|
|Snapbean, lima bean, and pole bean||6.5||100|
|Broccoli, cauliflower, brussels sprouts, cabbage, collards, Chinese cabbage, and carrots||6.5||175|
|Radish and spinach||6.5||90|
|Cucumber, squash, pumpkin, muskmelon, leaf lettuce, sweet bulb onion, watermelon, and strawberry||6.0 (watermelon) and 6.5||150|
|Southernpea, snowpea, English pea, and sweet potato||6.5||60|
|Kale, turnip, mustard, parsley, okra, bunching onion, leek, and beet||6.5||120|
|Spring Summer Crops||Target pH||N (lb./acre)|
|Tomato, pepper, potato, sweet corn, and eggplant||6.0 (potato) and 6.5||200|
|Snapbean, lima bean, and pole bean||6.5||100|
|Cucumber, squash, sweet bulb onion, watermelon, and strawberry||6.0 (watermelon) and 6.5||150|
|Okra and bunching onion||6.5||120|
This estimate is an estimate for the entire growing season of that crop, but you can’t, nor you should apply this amount at planting. This needs to be spread out over the entire growing season in multiple smaller applications for instance 20 lbs. of nitrogen 10 times for your tomatoes. This keeps you from losing expensive fertilizer through leaching during rain fall and makes sure your plants have enough nutrient throughout the growing season.
You may also be thinking, my garden is in rows how do I apply this fertilizer rate without wasting a lot in the row middles? In the commercial setting we use the linear-bed-foot method to convert per acre to per 100 bed foot. This can be a complicated system, but it can be simplified for your home garden. Most gardens are typically on a 3 ft row spacing, or something close to that, so dividing the square feet in an acre by the row spacing tells us how many linear bed feet per acre. However, a simpler method may be to just measure or walk-off your garden rows to find out how long they are. Then using a conversion table available from the extension office or in the companion electronic version of this newsletter you can easily convert the per acre fertilizer requirements for the crop you are growing into pounds per 100 linear bed feed. Based on the fertilizer formulation you are using, N-P-K (i.e. 10-10-10) this will tell you how much to apply per row in your garden either before planting or side-dressing after plants are stablished.
For example, a garden with 100 ft rows of snap beans will need 100 lbs. of nitrogen per acre for the season. If the snap beans are on a 3 ft row spacing and you wish to make five application of 20 lbs. of nitrogen using 10-10-10 fertilizer, you will need 1 lbs. of 10-10-10 fertilizer per 100 ft row. If you are scratching your head your probably not alone. The linear bed foot method can be hard to wrap your head around. Luckily that is what your extension office is for and all of the researcher at the University of Florida. Below you will see a conversion table for converting lbs. per acre into lbs. per 100 linear bed foot. Using this conversion chart and your row spacing for the crop you are growing you can easily figure out how many pounds of a certain nutrient per 100 linear bed foot you need from the IFAS recommended rate per acre.
To go back to our snap bean example, you know you want to apply 20 lbs. of nitrogen using a 10-10-10 fertilizer at planting to get your beans off to a good start. Well using a 3 ft row spacing for our beans we can use the below table to find out that 20 lbs. per acre of nitrogen converts to 0.14 lbs. per 100 LBF. Now this is not the amount of fertilizer you will need because you still need to convert lbs. of nitrogen to lbs. of 10-10-10 fertilizer. Because 10-10-10 fertilizer only has 10 lbs. of nitrogen per 100 lbs. of fertilizer we need to know how much to apply per 100 LBF in order to achieve our 0.14 lbs. of nitrogen per 100 LBF. To do this we convert using the same technique we would use for applying fertilizer on a per acre basis. We divide the pounds of nitrogen per 100 LBF by the pounds of nitrogen in our fertilizer then multiply by 100 ([0.14 lbs. of N per 100 LBF ÷ 10 lbs. of Nitrogen per 100 lbs. of 10-10-10] × 100 = 1 lbs. of 10-10-10 per 100 LBF). So, if we decided to use a 16-4-8 fertilizer we would need 0.87 lbs. of 16-4-8 ([0.14 lbs. of N/100 LBF ÷ 16 lbs. of Nitrogen per 100 lbs. of 16-4-8] × 100 = 0.87 lbs. of 16-4-8 per 100 LBF). This equation and relationship also holds true for phosphorus and potassium if those are the nutrients you may be targeting when fertilizing your garden.
Like I mentioned early in this newsletter this can get complicated if you really get into the weeds. So, feel free to always contact your local extension office and we can help you set up a fertilizer plan tailored to your garden and the crops you are growing.
Like fertilizing your garden, irrigating your garden can also be a tricky subject. Most people always wonder does my garden need water? How much should I water? How often should I water?
Improper irrigation can be problematic for a garden, as irrigation and adequate plant nutrition are tied together. Too much water can mean soil nutrients are leached out of the plants root zone and become unavailable to the plant. While too little water can stress plants and reduce their ability to uptake those soil nutrients. Most gardeners tend to error on the side of too much water.
So, like with fertilizer, if we take our understanding of commercial agriculture production, we can translate that to how we irrigate our home vegetable gardens. Commercial producers are well in tune with their equipment and understand if they run their irrigation system for a certain amount of time that translates to what would amount to a certain amount of rainfall. Because all home sprinklers are not created equal a general rule of thumb to follow is to never irrigate for more than two hours at one occasion. Anything greater than two hours is typically thought to increase leaching of nutrients that the plant requires from the root zone. In some instance when plants have high fruit loads or are close to harvest on very hot summer days, they do become wilted even with two hours of irrigation. In this case you can irrigate more time but that should be broken up in multiple occasion throughout the day. A great way to make sure you don’t over water and don’t spend all your time turning on and off sprinklers is to use a common garden timer which is available at most home improvement stores. A good diagnostic sign of over watering is plants will begin to appear wilted or start yellowing even with regular irrigation. For more information on irrigation see the electronic version of this newsletter.
Another important conservation for irrigation in a vegetable garden is that different plants have different water needs just like with fertilization. Some plants like pepper, okra might require less water than something watermelons or squash. To deal with this think about how you arrange your garden. Can you plant things with similar water needs together? Or plant crops that like drier conditions in drier parts of your garden. This can help ensure you don’t over water or under water any given crop.
Irrigation method can also play a major role in the success of your garden. For vegetable gardens the most efficient means of irrigation is drip irrigation. It conserves the most water, it puts the water where it needs to be, and it can help reduce weed and disease issues. However, this is more expensive and more time consuming to set up. The alternative is overhead irrigation, typically with sprinklers. This is the most cost-effective irrigation system. However, overhead irrigation loose more water to evaporation and weeds, is harder to control and can increase the risk of common disease like powdery or downy mildew. Both are still effective options but just be aware of the potential problems that can arise using overhead irrigation for your vegetables.
Vegetable Garden Guile Nebraska Extension
Nutrients and Fertilization Vegetable Handbook
Using the Linear Bed Foot System for Vegetable Production