# After-Planting Care

Program Contact: Tianna DuPont, Regional Specialist, Tree Fruit

(509) 663-8181 • tianna.dupont@wsu.edu

Young trees need water, sunshine, protection from insects and diseases, careful weed control, and a little fertilizer.

## Irrigation

Take it easy. Young trees do not use much water in the Spring. However, they also do not have much water available to them at any one time, as their root systems are limited. The tree will not use much water until it starts to grow, so take it easy in April and May. Short sets (four to six hours) applied every ten days or so when the weather is cool, then every week or so until mid-June will probably be adequate on all but the most sandy soils. On sand, you need more frequency, not more water, so shorten the sets.

After the weather gets warm in June and later, and the trees really begin to grow vigorously, both frequency and duration of sets must be increased. Seek information about how to adjust irrigation to the weather, the soil and the trees. As cooler weather returns, often starting in mid to late August, you should reduce your frequency of watering.

*Water Use by Week – 30 Year Average*

The young tree needs help avoiding root and collar rot, which is most likely to start in the Fall or Spring in overly-wet soils.

Finally, send the young tree into the Winter with moist soil to help prevent winter cold damage to the roots.

## Weed Management

Two year old peach tree—No weed control |
Two year old tree—weeds controlled |

There are no perfect weed control programs for young trees. Be ready to apply frequent, rather than powerful weed control sprays. Count on high weed pressure, as the sun is reaching the soil surface, fertilizer is plentiful, and weeds can start any time. Generally, you will need to apply a mixture of residual and contact material the first time you spray, then contact materials as needed. Spray each time weed reach about 6 inches in height, as taller weeds will get in the way of your spray boom.

Weeds can grow from 6 inches to a foot or more in a week, so do not put weed control off. Count on spraying at least three to five times the first summer. Young trees cannot tolerate competition. Mice love the protection of weeds, so you may prevent their dangerous buildup in the block with careful weed and cover crop management.

See the 1998 Summer Weed Control Plots

## Fertilizer for Young Orchards

If well watered and protected from weeds, young trees need far less fertilizer than we usually give them. A handful of fertilizer per tree is dangerous, as that rate works out to about 350 to 600 pounds of N per acre in the tree root zone. The first year tree can use no more than about a half tablespoon (of 34% N, a full tablespoon of 15.5% N) per tree per application.

### N Rates:

It is quite educational to look at the soil surface under the trees when you have finished with a “broadcast” application. Even the higher rates (80-100 pounds per acre of actual N at one time) do not look like a lot of fertilizer compared to the normal “handful” applied to a tree. A handful works out to be about 1/10 lb. of actual N when using 34-0-0.

The N rate PER SURFACE-TREATED ACRE a tree experiences in its root zone from a standard medium-sized handful of ammonium nitrate scattered in a zone 2 feet out from the trunk is about 690 lbs. of N per acre! No crop can use that much N at one time. This much N at one application will set the tree up for salt stress, which leads to moisture stress until the salt level drops. This is an important concept when you are growing a small tree with a small root system. It’s not the same effect when you place a handful of fertilizer over the large root system of a big tree.

If you want to apply the equivalent of 100 lbs. N per acre (still quite a lot, as far as the trees’ needs are concerned) in that zone of 2 feet out from the tree in all directions, you will have to cut the rate to TWO AND 3/4 LEVEL TABLESPOONS OF AMONIUM NITRATE ! (or six tablespoons of calcium nitrate.) Spread 2.75 tablespoons worth of 34-0-0, or 6 level tablespoons of calcium nitrate, in a 2 foot circular zone around a young tree and see what 100 lbs. N per acre looks like. You’ll be surprised. This TOTAL amount of product applied over the first half of the season, split into at least three ( on fine textured soils) or four to five (on sandy soils) applications will grow trees very well. So, one tablespoon of 34-0-0 per young tree, applied (for instance) three times, three weeks apart is plenty for the tree. Apply another tablespoon or two if this rate seems too little, but don’t expect increasing rates to lead to increasing tree growth.

When trees get into their second and third seasons, their roots develop a somewhat wider spread, so they can use the N applied farther from the trunk. If you want to apply the equivalent of 100 lbs. N per acre in a circular area THREE feet in all directions from the tree trunk, multiply all of the above numbers by 2.2. So, it will take a total of 6 level tablespoons of 34-0-0 per tree or 13 tablespoons of calcium nitrate per tree to give you the 100 lb. per-acre rate. Remember to split this into two to four applications, don’t apply it all at one time. Also, be sure that the product is spread relatively evenly under the tree in that 3 foot zone.

If you band fertilizer, the trees do not need more than 150 lbs. of actual N per acre per year, and that rate adjusted to the surface area in a six to eight-foot band along the tree row. Frequency of application is more important than high rates.

(See banding discussion below on this page).

On heavier soils, stop fertilizing by Mid-July, on sandy soils, cut it off by Late July. Give the trees a chance to set a terminal bud by early Fall.

### Report on a Young Tree Fertilizer Rate & Timing Trial

by Tim Smith, WSU Extension

As there seems to be a question on the best rates and application methods for nitrogen fertilizer in the tighter plantings of modern high density systems, I placed a N rate and timing trial in a 2 acre young block of Fuji on M 26 in Okanogan County, Washington. This was a replant site, but had good weed control and water management ever since it was planted. The soil is a fine sandy loam, and leaching of N was not as likely as we might expect in very sandy soils. There was very little N present in the soil, and relatively low organic matter. The trees were planted on a modified tatura system as whips, 3 feet apart in the row with alternating trees trained to a side of the trellis. Fruit was removed in the second season to encourage tree growth.

For two years I applied the N (by “belly grinder” spreader) evenly in a band about six or seven feet wide, down two widely separated rows for each treatment. Each treatment covers about a quarter acre. From each treated row, two widely separated sets of twenty trees were measured at planting and for two Falls after, for a total of 80 trees’ growth averaged for each N rate and timing.

The treatments include five different N rates, ranging from 100 to 400 pounds of nitrogen per acre. This rate per acre refers to the surface treated acre, that is the rate per surface area in the band treated. I didn’t think it was important to apply (or count) the N out in the grass where the M 26 roots did not yet reach.

All of the rates were split into five parts and applied every 3rd week starting at bloom and ending in July. In other words, the 100 lb. rate was applied as 20 lbs/acre. per application, 5 times, three weeks between applications.

Two of the rate treatments, 100 and 200 lbs. N per acre were also applied in two, rather than five, applications. One half of the total product was applied at bloom, the other half six weeks later.

PLOT RESULTS:

After two seasons (involving 10 two-acre hand applications of fertilizer and umpteen tree measurements) here is the grand rolling out of the results ( “% growth ” is the final trunk size divided by the starting trunk size times 100):

100 lbs. N per acre split into 5 applications | 247 % growth | |

150 lbs x 5 | 253 % growth | |

200 lbs x 5 | 264 % growth | |

300 lbs x 5 | 273 % growth | |

400 lbs. x 5 | 264 % growth | |

100 lbs per acre split into 2 applications | 269 % growth | |

200 lbs. x 2 | 248 % growth |

There was no visible or statistical difference between these treatments, either in the orchard or in the data. I apparently took care of all the young trees’ N needs with the 100 lb. per acre rate, even when only applied twice during the early season. It appears that we don’t need the high rates of N to get good tree growth. Other growing factors far out-rank the N rate when it comes to getting trees to grow well in their first two seasons. N presence is important, but the keeping the N rate high is not.

### Banding Example

For those who would like to apply the fertilizer concentrated in a band under the tree, you have to determine the rate of product which will give you the N rate you wish in the zone under the trees.

Step 1: Determine the percentage of the surface you are treating. Estimate the width of the band you will be treating, and divide by the row width. Treating a 7 foot wide weed control strip with a 16 foot row width works out to 7 divided by 16 or .44 of the surface area treated.

Step 2: Decide the total amount of actual N you wish to apply per season. I believe that somewhere between 100 and 150 pounds is plenty, even less depending on your soils’ ability to provide N.

Step 3: Calculate the pounds of product necessary to provide your planned amount of actual N. Divide the Pounds of actual N you plan to apply by the decimal equivalent of the percentage of N in the product you wish to use.

(The decimal equivalent to 33% is .33, …… 15.5% = .155,……. 20% = .20,…… etc.)

so, if you decided to use ammonium nitrate 34-0-0, and wanted to apply 120 pounds of actual N per season, you would divide 120 by .34 to see that you must apply 353 pounds of the product per acre.

Step 4. Adjust the per-acre broadcast rate to per acre banded rate. Since you are banding the product to avoid fertilizing the grass between the trees, you can reduce the per acre rate down to the rate that will be applied to the band under the trees (see step 1.) Multiply the gross amount you determined in step 3 by the fraction you determined in step 1.

So, if you want to apply 353 gross pounds for 120 lbs. of N to 7 out of 16 feet in each row, multiply by .44.

353 times 0.44 = 155 pounds of product per orchard acre.

Step 5: Divide this amount of product by the number of applications you plan for the season. Example from Step 4: If you plan to apply four applications, three weeks apart, divide 155 by 4, which will equal 39 pounds per application. O.K., call it 40, which is a half of the standard 80 pound bag.

Another example for ammonium nitrate:

100 lbs. N per acre, 34-0-0 = 100 / .34 = 295 pounds product per treated acre. 7 feet out of 18 feet = .39 of the area being treated. .39 X 295 lbs = a total of 115 lbs of 34-0-0 applied per orchard acre.

If you wish to apply this split into 3 parts, apply 115 divided by 3 = 38 lbs. of product per orchard acre each application.

for calcium nitrate:

140 lbs. N per acre, 15.5-0-0 = 100 / .155 = 903 pound product per treated acre. 8 feet out of 20 = .40 of the area being treated. .40 X lbs. = a total of 361 pounds of product per acre. Spit this poundage into as many parts as you feel will match your soil texture.

For young trees on finer textured soils, I suggest 3 applications (April, May, and June). 361 pounds / 3 = 120 per application.

If your soils are sandy or shallow, 5 applications, three weeks apart, starting after bloom will get the job done by mid-July. So, 360 divided by 5 = 72 pounds per orchard acre each application.

### How much is an orchard acre?

An acre is 43,560 square feet. (.40 hectare) This makes sense only if you know that there are 640 acres in a square mile, and a mile is 5,280 feet. Simple, eh?

So, to determine how many rows equal an acre, multiply the row length by the distance between rows, then divide that number into 43,560.

Example: your rows are 285 feet long, and spaced at 17 feet. 285 X 17 = 4,845.

43,560 divided by 4,845 equals about 9. So, you should be applying your chosen rate on each nine rows.