Ag Instructor Vic Martin:  Agriculture and “Micro” Things | Barton Community College

Ag Instructor Vic Martin:  Agriculture and “Micro” Things

Great Bend Tribune
Published April 28, 2019

The weather overall cooperated again this past week.  Soils are warming and perhaps and while some of the area received over an inch of rain, other areas were able to make progress.  Corn should/must go in the ground now.  However as this is written, an unsettled pattern is supposed to be upon us.    Wheat is jointing and progressing with the good air temperatures over the last week.  We are in “Goldilocks” territory for temperatures – not too hot and not too cold.  One last note – while not found yet in Barton County.  Rust is being found on wheat in several Kansas counties so attention for possible treatment is in order.  Last week’s column discussed fertilizer application and was about what are termed macronutrients – nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur.  This week’s discussion will focus on the “wee” things, which can may a large difference in crop yield and quality – micronutrients.

These nutrients are termed micro as they are needed in significantly lower amounts than the macronutrients.  The positively charged nutrients, cations, are iron, copper, zinc, manganese, and nickel.  The negatively charged nutrients, anions, are boron, chlorine, and molybdenum.  There isn’t much space here so let’s be brief and to the point.

  • There are soil tests for these nutrients, some are good and some not so much.  Often, if you suspect a deficiency, plant tissue samples are the only way to see what you have.
  • In many cases the deficiency isn’t a lack of the nutrient in the soil, it can be for something like zinc and boron, but due to soil chemical conditions.  Some are present but unavailable at high pH while others become unavailable at low pH (very acid soils).  Some like chlorine move easily in the soil and can leach with heavy rains on lighter (sandy) soils.  Some are found primarily with organic matter so low levels can create deficiencies.
  • What is challenging with micronutrients compared to the macronutrients is there is for many a fine line from deficiency to sufficiency to toxicity.  Meaning that over application can result in damage to or even the death of the plant.  A producer must be careful to know for certain they need the nutrient and not to over apply it to the soil or as a liquid for foliar applications.
  • Deficiencies are occurring for several reasons.  We have depleted the natural occurring amounts in the soil.  Crop yields continue to increase, taxing the soils ability to supply them.  Finally, producers used to get them for free when purchasing other fertilizers.  Today N-P-K fertilizers are much purer.  One last thing, it wasn’t terribly long ago we were still identifying what these essential nutrients were.  Nickel was determined in the last twenty years and while we know it is necessary for a plant to grow and complete it’s lifecycle, we don’t know had to really determine sufficiency amounts or soil deficiencies accurately.  And too much nickel is bad, potentially very bad for plants.  There may be more identified, we just don’t know.
  • Finally for today, sometimes there is a quick easy fix for a deficiency, sometimes we can’t easily correct the deficiency and have to do things like other crops or specific cultivars.

Next week’s column will discuss the likely micronutrient problems in Kansas and how to address them.

 

Published May 5, 2019
Part II

The weather was mixed the previous week.  Some parts south of Great Bend didn’t receive much rain and even rated as dry.  However, much of the area receive well over an inch last Sunday night and rains occurred throughout the past week.  This combined with cool temperatures resulted in wet soils and little progress in fieldwork.  Corn planting is now officially late and if the forecast is correct, unsettled weather should continue through at least midweek.  The Wheat Tour predicted an average yield for the state of a little under fifty bushels per acre, found nitrogen and sulfur deficient fields in South Central and Southwest areas of the state, the wheat is behind the average in terms of development, and leaf diseases are starting to show up.  Producers are not late with soybeans and grain sorghum but work is stacking up.  Finally, the rule of thumb is the first alfalfa cutting should occur around mid-May at about 1/10 bloom.  This is normally the largest cutting and the one preferred by horse owners.  Now, to finish last week’s topic on micronutrients (iron, zinc, copper, manganese, nickel, molybdenum, boron, and chloride).

These nutrients, needed in small amounts are becoming more important as producers work to increase yields and natural soil stores are drawn down.  So how do producers determine what they need and how to address the problems?

  • For the macronutrients, we have adequate soil tests for nitrogen, potassium, phosphorus, calcium, magnesium, and sulfur.  However, work is still being done to determine effective soil tests to relate soil levels to actual nutrient availability for the crop.  The best we can do for many is place the level in a broad range and determine deficiency, sufficiency, or excess.  For example, chloride levels are determined in a range and applied based on the range they fall in.  Not such a big deal with nutrients like chloride where a bit too much is of little concern.  However, with some, like manganese, an excess could harm the crop.  For some nutrients, like iron, an important bit of information is the soil pH where a high pH is the cause of the deficiency and not the actual iron concentration in the soil.
  • For some producers farming on lighter, i.e. sandier soils, an initial diagnosis of a deficiency of soil chloride and/or zinc for corn, tells them what they need to know.  A simple yearly, moderate application of the nutrient is needed without further testing.
  • The best test for many micronutrients doesn’t involve the soil at all but plant tissue testing.  For young plants it’s typically whole plant samples.  As the plant grows, there are instructions for what plant part to take, from where, and how big a sample to collect.  Sometimes, you can correct the deficiency that season while for certain nutrients it’s too late but at least the producer knows for next season.
  • Once you have identified the deficiency there are a variety of options based upon the deficiency, soil conditions, and plant growth stage.

Next week’s column discusses common micronutrient deficiencies for Kansas crops and how to address these issues.

 

Published May 12, 2019
Part III

To state the obvious, it is wet, very wet.  Much of the area received well over five inches of rain last week.  With the exception of producers and sandy soils, fieldwork is a ways off, especially with the projected rains this week.  Corn planting is way behind normal, not just in Kansas but also throughout much of the Corn Belt.  Yields will suffer.  The area is still okay for soybeans and grain sorghum but only time will tell.  First cutting alfalfa, normally the highest tonnage, will likely be delayed.  Crop duster are out with wet fields.  Wheat is heading out and while the cool wet conditions are beneficial, they help promote leaf diseases, which are showing up around the state.  Fungicide decisions need to be made soon.  Now onto today’s topic, finishing up plant micronutrients.  So what are the possible deficiencies in Kansas and what can producers do?

  • Zinc - Producers on the sandy soils in the area, especially under irrigation, apply zinc as a regular part of their fertility program.  Deficiencies are most common in corn and very occasionally in soybeans.  Conditions favoring zinc deficiencies include sandy soils, cool wet conditions, pH readings above 7, and high soil phosphorus (P) levels (especially combined with in-row P.  Zinc can be broadcast as a chelate or zinc sulfate.  It may be applied as a starter fertilizer or a foliar application if symptoms develop.  Broadcast applications normally last for several years.
  • Chloride – Corn, grain sorghum, and especially wheat are subject to chloride deficiencies, especially on sandy soils and soils with high potassium levels where potassium chloride (potash) fertilizer isn’t used.  The need for the chloride ion and the response to the crop are highly variety/hybrid dependent.  Responsive cultivars have demonstrated up to a twenty percent yield increase in wheat with similar significant responses for other grass grain crops.  Any available source works well but in row placement should be avoided.  Yearly applications are necessary since chloride is an anion.
  • Boron – Boron deficiencies are most common for alfalfa but may occasionally show up in corn.  The deficiency typically on sandy soils.  Foliar sprays should be avoided as should close contact with seed.  Broadcasting, dry or liquid, alone or mixed with other fertilizers or pesticides is acceptable. 
  • Iron – Iron deficiencies generally occur on high pH soils, southwest Kansas for example, where there isn’t a lack of iron in the soil but it is unavailable.  Other factors contributing to a deficiency include soil low oxygen levels due to compaction or waterlogged soils, high temperatures or excessive amounts of phosphorus copper, zinc, or manganese.  Soybeans are most sensitive.  While foliar applications are possible, they are expensive and not consistently effective.  A better solution is to select tolerant soybean varieties, or plant less sensitive crops such as corn or wheat. 
  • Molybdenum  - This nutrient is key for nitrogen fixing plants, alfalfa and clover, as it is needed by the Rhizobium bacteria in the nodules to provide the plant with nitrogen.  Low pH can lead to deficiencies.  At pH levels above 6, there shouldn’t be a problem.  A low rate mixed with seed or a very dilute foliar spray.  Caution must be taken as levels above 10 ppm can be toxic to ruminants.  Fortunately deficiencies are rare.

Remember that these nutrients are needed in small amounts and proper sampling is necessary to determine deficiencies.  And excessive amounts of these micronutrients can be detrimental to crops and a producer’s pocketbook.

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