Tag: fertilizer

This ‘n That

Grading finals, looking at roots, and planting seeds is consuming my time this spring, but I have just a few things to share today which might be interesting.

So, as those of you who follow this blog know, I love peanuts.  This year we’re planting out a bunch of new varieties, a few of which are extremely interesting.  Believe it or not there are not only red and pink peanuts but also black, white, and mottled peanuts.  We have these on order — when they come in I’ll post a picture.  When we introduce Minnesota Boiled Peanuts at the State Fair in a few years (that’s the goal anyway) the plan is to introduce a wide variety of really unique looking peanuts.  Fingers crossed they can live here!

Here, at the University of Minnesota, we do a really great job of telling people that, when they fertilize their grass, they should keep the fertilizer on the grass and not on the sidewalk — SO WHY CAN’T THE UNIVERSITY TEACH THE KIDS WHO APPLY THE FERTILIZER TO THE UNIVERSITY’S LAWNS TO KEEP THE DARN FERTILIZER OFF OF THE PAVEMENT?!?  Last week as I walked in I heard a crunching sound coming from my feet.  When I looked down there was a little pile of fertilizer on the sidewalk.

Believe it or not, judiciously fertilizing your grass actually helps prevent fertilizer run-off.  That’s because grass with a weak root system (as occurs in the typical lawn when you don’t fertilize at all) won’t be able to hold the soil as well — so you get more erosion.  So do fertilize your lawn, just don’t go nuts.

About that whole tree in the lung thing which I posted last week?  Yeah — It’s BS.  How do we know it’s BS?  No obvious roots on the tree and the tree’s needles were green (you don’t get green plants without sunlight). Personally I think this is some kind of odd cry for attention, but I guess it’s possible that the guy swallowed a cutting while he was shearing/pruning trees.  HOWEVER, there are documented cases where seeds will germinate in a persons lung — Usually the person has a compromised immune system.

Guano

One of the best organic fertilizers out there – at least in terms of how plants respond to it —  is bat guano.  As most of you probably already know, bat guano is made of bat droppings.  What you probably don’t realize is that bat droppings need to be aged for a while in an arid environment before they become guano.  Caves provide the perfect environment for this to occur, and so that is where most bat guano comes from.

Because guano needs to be aged in special surroundings before it is used it is not a rapidly renewable resource.  Instead it’s kind of like peat in that it takes anywhere between decades and thousands of years for the raw material from which it is made to develop into the stuff that we use.  Furthermore, by harvesting bat guano we can actually damage the ecosystems present in the caves from which the bat guano is harvested.  Think about it – bats generally feed outside the cave, so when they defecate inside the cave they are actually bringing new nutrients into the cave – nutrients that other creatures can use.  Whole ecosystems are based on this poo!  So when we harvest bat guano from a cave what we are doing is disturbing a specialized ecosystem – a very unique system.

So am I encouraging you away from bat guano?  No more than I would encourage you to consider reducing your usage of peat – or of oil — or any other non-renewable resource.  I can’t deny that it’s a great fertilizer, but if you want to use an organic fertilizer why not at least consider one that is renewable instead of one that is from a limited resource and which may cause harm to a unique ecological system?

Proposed phosphate fertilizer ban – a dissection of the criticisms

A few brave souls gave Friday’s homework assignment a good shot.  Ryan did a nice critique of the bullet points; Kenny did a little digging on WFFF, the organization behind the email; and Tom chimed in with the fact that Israel managed to do this a long time ago without impairing plant health.  Gold stars for all!

Here’s my initial analysis of the statements made, based on reading the bill (which you should do if you haven’t yet; it’s neither long nor difficult to understand):

WFFF: 1) The intent section contains scientifically inaccurate statements, creating a false precedent that turf fertilizer is a significant surface water pollutant and is not necessary for a healthy lawn.

The bill: The legislature finds that: (a) Phosphorus loading of surface waters can stimulate the growth of weeds and algae and that this growth can have adverse environmental, health, and aesthetic effects; (b) Lawn fertilizer contributes to phosphorus loading. Limits on fertilizer containing phosphorus can significantly reduce the discharge of phosphorus into the state’s ground and surface waters; (c) Fertilizer containing no or very low amounts of phosphorus is readily available and maintaining established turf in a healthy and green condition is not dependent upon the addition of phosphorus fertilizer; and (d) While significant reductions of phosphorus from laundry detergent and dishwashing detergent have been achieved, similar progress in reducing phosphorus contributions from fertilizer has not been accomplished.

LCS:There is no identification of the “scientifically inaccurate statements” in the intent section, and as far as I can tell the statements are accurate.  The WFFF statement also misdirects the reader into believing that the intent section states that “turf fertilizer…is not necessary for a healthy lawn” when in fact the section (point c) states that healthy lawns can be maintained with low phosphorus fertilizers.

WFFF: 2) It grants the authority to regulate fertilizer sales and use to the Department of Ecology (Currently, the Department of Agriculture regulates fertilizer content and registers it for sale.)

LCS:  It is unclear why this is a problem; both are state agencies.

WFFF:  3) It changes the definition of fertilizer used by the Department of Agriculture, creating confusion.

LCS:  Where is the confusion?

WFFF:  4) It is inconsistent and will be ineffective because it exempts “natural organic sources.” Organic products are high in phosphorous. The ecosystem cannot tell the difference. All fertilizer should be regulated equally.

LCS:  This is misleading.  Not all organic products are “high in phosphorus”.  Furthermore, the phosphorus in organic matter is usually bound up in compounds that must be degraded before the phosphorus is available, making organic matter more of a slow release material.

WFFF:  5) It fails to recognize the expertise of trained lawn care professionals, who should not be prohibited from providing quality service to their customers, including publicly owned golf courses, parks, and sports fields.

LCS: How is the “expertise of trained lawn care professionals” relevant to the bill, and how is this expertise not being recognized?  In fact, the bill creates increased expert oversight by working with Washington State University Extension specialists (faculty) in setting standards for applying phosphorus fertilizers based on soil test results.

WFFF:  6) As written, it bans the use of phosphorous fertilizer for forestry, house plants, shrub beds, golf courses, sports fields and other uses. It is unclear as to private commercial property.

LCS: Unless there is a demonstrated need for phosphorus fertilizer (i.e. a deficiency verified by soil testing), there is no need to use it.  The routine use of phosphorus fertilizer without establishing a need is the behavior this bill seeks to limit.

WFFF: 7) It bans the sale of phosphorous fertilizer for flower and vegetable gardens, forestry, house plants, shrub beds, golf courses, sports fields, and many other uses.

LCS: Again, unless there is a demonstrated need for phosphorus, it should not be routinely added to any garden or landscape.

WFFF: 8) It bans retailers, including farm stores and ag dealers, from displaying any type of fertilizer containing phosphorous.

LCS: This does not preclude people from purchasing it.

WFFF: 9) It fails to address the primary causes of impaired water quality. Regulating something because it’s easy without addressing root causes of the problem accomplishes nothing.

LCS: This statement fails to inform us what the “primary causes of impaired water quality” are. How do we know that fertilizer runoff is not one of these causes?

Insects and Fertilization

Linda got a few comments and questions on her post a couple of weeks ago on fertilization and insect resistance.  This is an issue I’ve been peripherally involved with over the years so I wanted to share a few thoughts.  First, the relationship between plant nutrition and insect resistance is extremely complex.  We often have difficulty predicting how a plant is going to respond to fertilization, let alone predict how an insect is going to respond to how the plant responded.  I haven’t kept up but Koricheva (2002) reported over a dozen different theories have been proposed to explain insect response to plant nutrition.  One of the factors that makes it difficult to generalize about plant/insect interactions is that various insects feed on different plant parts in different ways; some are leaf feeders, some suck sap, some bore into wood, some feed on seeds or cones.  How an insect feeds can affect its response.  To stick with an illustration I’m more familiar with, we can look at insect response to plant drought stress.  Bark beetles are widely known to key in and attack pines and other conifers under drought stress but pine tip moths prefer succulent buds and new growth and are more likely to attack well watered trees.  It’s not unreasonable to think there are similar differences with nutrition.

 

Nevertheless, as noted above, there have been attempts to come up with general theories on the effect of plant nutrition on insect resistance.  One of the most widely cited is the Growth-differential balance theory proposed by Dan Herms and Bill Mattson  (“The dilemma of plants: to grow or defend.”  Q. Rev. Biol. 67: 283-335).  A quick check on Google Scholar indicated this paper has been cited by over 1,400 other papers, which is an astounding number and speaks to its influence.  The basic premise of the theory, as suggested by the title of the paper, is that plants make a trade-off between allocating carbohydrates for growth or allocating carbohydrates for secondary defense compounds.  Dan Herms subsequently applied the theory in synthesizing the literature on woody ornamentals in his 2002 paper,  “Effects of Fertilization on Insect Resistance of Woody Ornamental Plants: Reassessing an Entrenched Paradigm.” (Environmental Entomology 31(6):923-933.).  I have heard some arborists and others use this paper to argue that we shouldn’t fertilize landscape trees at all.  The problem is they oversimplifying the theory – which is understandable, this is pretty heady stuff.  They get the ‘trade-off’ idea; if plants grow fast they produce lots of yummy stuff for bugs.  But what is often overlooked – even though Herms makes a point to say it – is that when nutrition or other plant resources are low; there is no trade-off.


This figure from Herms and Mattson illustrates the idea.  If nutrients are deficient and we fertilize a plant the plant may increase growth and secondary compounds; it’s not always an either/or situation.  The bottom-line remains the same;  nutrient deficient plants can benefit from fertilization or correcting the factors (e.g., alkaline pH) that made them deficient in the first place.

Koricheva, J. 2002. The Carbon-Nutrient Balance Hypothesis Is Dead; Long Live the Carbon-Nutrient Balance Hypothesis? Oikos 98 (3): 537-539

Proposed phosphate fertilizer ban

Today I received an email alerting members of Washington Friends of Farms and Forests to a proposed ban on phosphate-containing fertilizers in the state of Washington.  Here’s part of the text of the email (I’ve removed underlining, bolding, highlighting etc. so this reads as objectively as possible):

“Concerns with the HB 1271 & SB 5194 banning the sale of fertilizer containing phosphorous:

1) The intent section contains scientifically inaccurate statements, creating a false precedent that turf fertilizer is a significant surface water pollutant and is not necessary for a healthy lawn.

2) It grants the authority to regulate fertilizer sales and use to the Department of Ecology (Currently, the Department of Agriculture regulates fertilizer content and registers it for sale.)

3) It changes the definition of fertilizer used by the Department of Agriculture, creating confusion.

4) It is inconsistent and will be ineffective because it exempts “natural organic sources.” Organic products are high in phosphorous. The ecosystem cannot tell the difference. All fertilizer should be regulated equally.

5) It fails to recognize the expertise of trained lawn care professionals, who should not be prohibited from providing quality service to their customers, including publicly owned golf courses, parks, and sports fields.

6) As written, it bans the use of phosphorous fertilizer for forestry, house plants, shrub beds, golf courses, sports fields and other uses. It is unclear as to private commercial property.

7) It bans the sale of phosphorous fertilizer for flower and vegetable gardens, forestry, house plants, shrub beds, golf courses, sports fields, and many other uses.

8) It bans retailers, including farm stores and ag dealers, from displaying any type of fertilizer containing phosphorous.

9) It fails to address the primary causes of impaired water quality. Regulating something because it’s easy without addressing root causes of the problem accomplishes nothing.”

So, readers and colleagues, do a little homework over the weekend.  Look at the bill itself (both the house and senate bills are the same; the link is for the house bill).  Are these nine concerns valid?  Discuss.

Fast food is unhealthy for plants, too

In early December, I posted my thoughts about fertilizing crops vs. landscapes.  An anonymous reader asked if we could follow up by discussing the relationship between excessive fertilizers and plant susceptibility to pests and disease.  It’s taken a month to get the scientific literature (and my act) together, but here it is.

There are decades’ worth of articles about the direct relationship between increased nutrient availability and increased susceptibility to pests, disease, and disorders.  One of the earliest articles linked the incidence of celery blackheart to over-fertilization.  Since that time, researchers have found similar causal relationships in vegetable crops such as rice, onions, and soybeans, ornamental crops including poppies, and perennial orchard crops such as nectarines.  Unfortunately, there’s been no research on landscape species.

Happily, the way plants react to excess nutrient levels is generic – so we can apply the findings in the agricultural literature to landscape situations.  Just like kids and candy, plants will greedily take up all the available macronutrients their roots can find, especially nitrogen and phosphorus.  (It makes NO difference is the fertilizer is organic or inorganic.)  Plants in highly nutritive soils respond with lush vegetative growth – and fewer flowers, by way.  Less metabolic energy is put into protective compounds, so these succulent new leaves and shoots are prime targets for all kinds of unwanted plant-eaters and foliar pathogens.

As with so many things in life, moderation is the key.  For routine landscape needs, use woody mulches rather than fertilizers and nitrogen-rich composts.  This “slow food” approach not only benefits your plants, but provides ideal habitat for mycorrhizal species, which have been shown to help restrict root uptake of excessive nutrients, while assisting with uptake of less available ones.

Of Worms and Fertilizers

Today I’m going to write about fertilizers and worms.  The purpose of this post is not to encourage you to use fertilizers.  I agree wholeheartedly with Linda’s post – we don’t need many of the fertilizers which we’re using.  Still, it’s important to know the facts about anything that you’re doing (or not doing) to and for your garden, and to do them (or not do them) for the right reasons.  With that in mind, I’ve been reading about worms and fertilizers for the last few days and wanted to let all of you know the basics of what I’ve been reading, because it is somewhat contrary to what many gardeners believe.

Before we begin let’s get one thing straight — worms are basically good for your garden and your plants in general.  We like them!

Over the years I’ve heard all kinds of comments about how inorganic fertilizer is bad because it kills worms or drives them away.  For the most part I’ve just accepted these claims as generally true because it seemed to make sense and I didn’t have a reason to study it further (I don’t write about worms much, and I’ve never spent any time doing research on them – still, I have to admit that this is no excuse for ignorance).  The only contrary words I’d ever heard spoken about the reality of what fertilizers do to worm populations had come from a soil scientist friend of mine who told me, in casual conversation, that he didn’t believe that fertilizers were bad for worms at all, except, perhaps in the very short term if they got some fertilizer directly on them.  Rather, he believed that, because fertilizers encouraged the growth of plants, fertilizer use would actually increase worm populations because it would increase their food supply.

After reading through a few papers it looks like my soil scientist friend was right.  Here I’m going to summarize my general impressions about these papers into a few sentences – not exactly fair because the relationship between worms and fertilizers isn’t completely straightforward – but hey, this is a blog!  Basically, if you add fertilizer of any sort to your soil you will ultimately increase worm populations because you will encourage the growth of more plant material.  More plant material, over the course of time, means more organic matter for worms to eat.  Generally organic fertilizers seemed to be preferred by worms (probably because they include lots of organic material along with the nutrients which they offer), but overapplication of fertilizer (organic or inorganic) could be bad for worm populations, at least in the short term.

So, in a nutshell, judicious fertilizer use shouldn’t affect worm populations negatively.  Still, why add fertilizer at all if you can avoid it?  Mulch and compost – worms will definitely enjoy that!

Fertilizers, crops and landscapes

Last week Jeff wrote about the dangers of using “balanced” fertilizers, especially in reference to phosphorus content.  Comments quickly followed about using fertilizers in many situations – on farms, in container plants, on trees – and so on.  One of the latest comments came from Nick and began “I don’t usually recommend fertilizer for perennials or woody plants to consumers. In most cases they aren’t needed.”  And this leads into today’s topic.

Many of the horticultural practices we use in our gardens and landscapes have, unfortunately, been derived from agricultural crop production.  Whether you’re growing a field of wheat, garden tomatoes, or containerized shrubs your goal is maximizing crop production.  By its nature, this is an unsustainable practice because it requires continual inputs of water and nutrients at higher levels than would naturally occur.

But this is not how you should care for landscape trees and shrubs, and why Nick’s comment was a good one.  You don’t need to routinely add fertilizer to these plants; they don’t need it to grow normally.  What we should be doing in landscapes is preventing nutrient deficiencies.  Once you have a soil test in hand, you’ll know what nutrients may be too low (or too high) and how soil pH will affect that.  For most of us, this may involve occasionally adding one of a few nutrients (most commonly nitrogen), or perhaps acidifying the soil to improve nutrient availability.

 How do you know when to add nitrogen to established landscape plants?  Let your foliage do the talking. If leaves are uniformly yellow, small and sparse, you might have a nitrogen deficiency.  This will be most common in the mid to late summer, when plants are growing most rapidly and competing with one another for resources.  Be sure this symptom is wide-spread, however.  If it’s just one plant showing deficiency symptoms, it’s probably not a landscape issue.

 

Balanced fertilizers are usually out of balance

I’m in the midst of grading papers for my nursery management class, and something that I’m running across is an incredible number of papers where the students are recommending balanced fertilizers.  Why are they doing that?  Or maybe an even better question is, what is a balanced fertilizer?  A balanced fertilizer is a fertilizer which has three numbers which are about the same, like a 10-10-10.  The problem with balanced fertilizers is that they are much higher in phosphorus than what most plants need — at least in relation to the amount of nitrogen and potassium which plants need.  Especially here in Minnesota, where there is usually plenty of phosphorus in the ground, this extra phosphorus serves no purpose except to pollute waterways.  We have got to break the cycle of just assuming that a balanced fertilizer is the way to go.  I get to see a lot of soil tests from old agricultural fields where balanced fertilizers were used for years and years.  Usually 10-10-10.  What I usually see — with very few exceptions — are phosphorus and potassium levels which are either very high or off the charts entirely.  Phosphorus and potassium don’t move readily in the soil while nitrogen does, so every year that you add 10-10-10 in the appropriate amount for your plants needs for nitrogen you’re adding too much phosphorus and potassium.  Any extra nitrogen which you add will move through your soil, but P and K will build up year after year (and some will run-off into gutters and drains).  So what do I recommend?  I like a ratio of about 5-1-2 or 5-1-3 for an N-P-K ratio in a general use fertilizer.

Are Fertilizer and Insecticide Spikes a Good Idea?

One of the products that I often hear gardeners raving about are their fertilizer / pesticide combination spikes which are supposed to not only feed your plants, but also kill all of the insects which attack them.  I, personally, have not used these products, but I’m generally the kind of person who says “If it works for you then keep using it”.  Still, these spikes bug me a little.  Here’s why.

First of all I should point out that I’m not opposed to fertilizer spikes by themselves.  I’m a little concerned that fertilizer should be spread out instead of concentrated in one place, but still, I don’t consider them that bad.  The insecticides used for these spikes is where I have the problem.  Once upon a time these spikes were made with a chemical called disulfoton (aka disyston) which is bad news.  It’s a water soluble chemical which is highly toxic to people.  If you have an old package of fertilizer / insecticide spikes around there’s a good chance they were made with this chemical.  Do yourself a favor and get rid of them.  This stuff is really toxic and not to be messed with.  On the other hand, if you’ve purchased fertilizer / insecticide spikes recently, then the active insecticide in those spikes is probably imidacloprid.  Imidacloprid is a mixed bag when it comes to safety.  It’s not nealy as toxic as disulfoton, but it’s not non-toxic.  It has been banned in Europe for a variety of reasons, the most important of which seems to be that it was implicated in the collapse of bee hives (imidacloprid is systemic insecticide so it will get into a plants pollen where honey bees could eat it).  At this point it hasn’t been ruled out as having something to do with hive collapse here in the states — though if it does have a role it does not seem to act alone.  It can also affect other beneficial insects who feed on pollen.  Additionally, it has been known to control some pests while allowing mites to go crazy — in fact, it may even increase the rate of mite egg laying.

But imidacloprid is an effective insecticide which works against a wide range of insects which you that you might find on your plants.  It is much safer than many of the older systemic insecticides, and it isn’t readily translocated to fruits (a problem that many people are concerned about with systemic insecticides is the movement of these insecticides into the fruit itself where it can’t be washed off — Imidacloprid is translocated to fruits –just not that much — it moves in the xylem and fruit takes up mostly phloem).

So these spikes are one of those things that I’m wary of.  Not to say you shouldn’t use them, but be aware of what they are and what they could do before you buy them.