Fertilization Print

Production advice — of interest to Growers


In The Netherlands, allowable nitrogen levels for nursery production are relatively low.  It is therefore important to use the allowed quantities as efficiently as possible.  As well as type of fertilizer, quantity, timing, application method, and soil type must all be taken into consideration.

Delayed application of organic fertilizers

Organic fertilizers are generally applied in the nursery when a field is empty.  In this time frame large quantities are applied to deal with a multi-year crop.  As the organic matter breaks down, nutrients become available.  This mostly happens, however, during the time that the newly planted crop still has a limited need for nutrients.  In other words there are more nutrients available than the plants are capable of absorbing, resulting in nutrient leaching.

By applying the organic matter throughout the growing time, it is possible to match nutrient availability more closely to the crop’s requirements.  It will also increase the organic matter in the soil.  A special application method is ‘row application’ for fruit and shade trees, which has the added benefit of reducing weed growth.

Apply compost instead of liquid or dry manure

Organic fertilizers are applied in order to maintain the organic matter of the soil as well as to slowly introduce nutrients, which takes place as the organic matter breaks down.

According to the European legal usage limits for manures, a maximum of 375 lbs. (170 kg) of nitrogen and 185 lbs. (85 kg) of phosphorous can be applied per 2.5 acres (one hectare).  In order to comply with the legal limits, the applied amount of nitrogen must be multiplied with a co-efficient (depending on the type of organic fertilizer used) to determine the amount of workable nitrogen.  Large quantities of animal manures (liquid or dry) are required to maintain organic matter levels, which result in using up a large portion of the allowable nitrogen and phosphorous allocations.  If additional nutrients are required that season, no allocation will be available.

Delayed application of organic fertilizers

Organic fertilizers are generally applied in the nursery when a field is empty.  In this time frame large quantities are applied to deal with a multi-year crop.  As the organic matter breaks down, nutrients become available.  This mostly happens, however, during the time that the newly planted crop still has a limited need for nutrients.  In other words there are more nutrients available than the plants are capable of absorbing, resulting in nutrient leaching.

By applying the organic matter throughout the growing time, it is possible to match nutrient availability more closely to the crop’s requirements.  It will also increase the organic matter in the soil.  A special application method is ‘row application’ for fruit and shade trees, which has the added benefit of reducing weed growth.

Apply compost instead of liquid or dry manure

Organic fertilizers are applied in order to maintain the organic matter of the soil as well as to slowly introduce nutrients, which takes place as the organic matter breaks down.
According to the European legal usage limits for manures, a maximum of 375 lbs. (170 kg) of nitrogen and 185 lbs. (85 kg) of phosphorous can be applied per 2.5 acres (one hectare).  In order to comply with the legal limits, the applied amount of nitrogen must be multiplied with a co-efficient (depending on the type of organic fertilizer used) to determine the amount of workable nitrogen.  Large quantities of animal manures (liquid or dry) are required to maintain organic matter levels, which result in using up a large portion of the allowable nitrogen and phosphorous allocations.  If additional nutrients are required that season, no allocation will be available.

It is therefore better to use low nutrient materials, such as compost, to maintain organic matter levels in the soil.  Compost has a low co-efficient for nitrogen under the allocations, as well as low levels of nutrients.  Also half of all the phosphorous applied in compost is not counted towards the allocation to a maximum of 7.7 lbs (3.5kg) per tonne of dry matter.

Use slow acting nutrients

To ensure good growth it is necessary for plants have access to the right nutrients at the right time. The terms “slow release nutrients” and “controlled release nutrients” can be used interchangeably.  Materials that need to be broken down by micro-organisms before nutrients are released are slow-release nutrients.  However, this does not mean that the nitrogen is released in a controlled manner.  Coated nutrients are often called “controlled release fertilizers”.  The principle is that the nutrients are released gradually.  Aside from nitrogen, they also contain other nutrients.  Several varieties are available with controlled release over a period of from three to 12 months.

Side dress nitrogen on the basis of crop-specific target and N-mineral

In the guide “nutrient advice for nursery production in the field” a target number has been established for each nursery crop based on crop needs: the crop target.  From this, the nitrogen already present in the soil needs to be deducted.  In other words: side-dress nitrogen amount = target – nitrogen in soil.  By having soil tests done for nitrogen twice per growing season, exact quantities of required nitrogen can be determined and added as needed.  This is called the Nitrogen Side dress System.

Use selective side dress application instead of broadcast

By using the side dress application, nutrients are placed close to the roots.  The intent is to increase the chance of uptake and to reduce nutrient losses.  It is important to make sure the nutrients are not concentrated too highly, nor placed too close to the roots, in order to avoid salt damage.  In practice this method is usually used for phosphorous application, but it can also significantly increase the efficiency of nitrogen application.

Sow a catch crop between the trees

In some nursery crops it is useful to be able to retain the available nitrogen longer.  This can be done by sowing a catch crop.  In shade and fruit tree crops, a lot of experience has been gained with the use of winter barley and annual ryegrass as catch crops.

The idea of a catch crop is to absorb the nitrogen that is still present in the soil profile at the end of the growing season and thus prevent leaching.  The catch crop has to be winter hardy in order to accomplish this.

A catch crop is sown in the late summer and is not fertilized. In the spring the crop is either killed physically, or with a herbicide, and worked into the soil profile.  In the soil the plants are then broken down by mineralization, and all the nutrients once again become available.

New brochure about sustainable nutrient application

The management techniques mentioned in this article are part of a new brochure from PPO Boomkwekerij called “Get more from your fertilization”.  The brochure can be downloaded  from www.ppo.wur.nl although you might need to get it translated into English to get the most out of it.

source:  De Boomkwrkerij
 

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