Fall Nutrient Management

Hard to believe folks, but another season has flown by. I drove 30 miles on back roads from my place in the south-side of Remington, Indiana all the way to Lafayette, Indiana and I saw 2 combines getting the last of the corn that was standing in two different farms.
There are some soybeans still standing just waiting for the soil to dry out after the inch of rain we had last Friday/Saturday.
I'd like to touch a few points about soil sampling and soil nutrient management, since it is a key time of the year to manage those.
First of all, soil sampling as I have defined it before is one of the most important practices we can do when managing our crops. Whether we're growing grain, vineyards, orchards, vegetables, etc.
Now, I won't describe HOW to take a good representative soil sample since I already did in the following article soil sampling
As I just wrote, Fall is a great time of the year to do this. I personally recommend dividing the fields into uniform areas (as much as 10 acres). There are several factors that we can take into consideration when deciding our sampling areas:

• Soil slope: soil depth will vary with the slope and elevation. We should expect to have high-yielding zones in lower areas of the field and less-yielding zones in higher less-deep areas due to soil depth. One way I admire the American farmer (specially the Iowan) is the architecture they apply when building up terraces when farming on hilly areas. 
• Texture: different soil types within the same farm. Soil texture won't change in a lifetime so if there are identified areas where the sand-lime-clay% ratio varies those should be managed differently. 
• Management type: Areas with similar management strategies. 

This should be done when the soil is not excessively wet and not before ANY type of fertilization or lime application, otherwise you'll be wasting your time by doing this.

The way I look at a crop when I stand in front of it is: A crop is a reflection of the soil nutrition, water content, soil condition, weather and genetic potential of it. 

This can be expressed in yield and yield can be managed in yield maps. 

I strongly recommend comparing yield maps with soil sample results. If you can avoid applying a regular rate of fertilizer after harvest, you'll be saving $$. Some areas may not hardly need any fertilization while others will probably need more than your overall rate. 

I will be talking about sources of nutrient and ways to fertilize, along with interpreting soil sampling results. 

Thanks for reading my blog! 

Temperature Stress in Corn. How to deal with it

When driving across and around the Mid West early in the season, everything "looked" sort of normal for many. Soil moisture wasn´t the best in many areas. Warmer-than-normal temperatures struck later in the winter which generated a planting rush.
It's been the driest year for over 20 years. But let's talk about what I like the most, Agronomics and Physiology of crops.

Crops like Corn (a grass) has a type of leaf that facilitates fast reactions to changes in Tº and %RH (Relative Humidity) in the air. I define the Leaf as the Heart of a plant (any plant).
The type of venation that the foliage has is defined as a "Paralell Venation" with a mid rib in the center of the leaf and a lanceolate form.
That allows the corn leaf to react fast to any change.
Let's always remember that a plant does NOT take its water from the leaves!!! so it doesn't matter how much dew there is in the early hours of the day in the whorl and leaves, if the soil is lacking moisture the plants will be under a stress. 


Let's imagine a hot summer day, a real hot one. 
Tº: 102F
%RH: 95%
Heat Index: 108F
Water: It hasn´t rained in a week and it's been hot every day.

What could we expect from the plants to do? Photosynthesis? Uptake water and nutrients? Elongate their inter-node sections? keep the same leaf axil angle as always?

Well under these conditions several processes are triggered.

1. Plant synthesizes acids in the stomes to provoke a temporary closure of them. This provokes the plant to stop interchanging O2 and H2O with CO2 with the atmosphere. 
2. Photosynthesis ceases as no gaseous exchange is taking place in the leaves. Carbohydrate mobilization might shift as the main sink changes (a sink is a structure that at a specific growth stage is requesting or demanding the higher amount of energy and sugars from the leaves). 
3. Hormone balance gets affected. Plant ceases Citoquinine (used in cell division and plant Growth), Auxines (used in tissue elongation) and Giberelines (plant Development) synthesis and starts synthetizing Absicic Acid (defoliation) and Ethilen (plant stress and maturation).

There are very many more changes and processes that are being triggered during a stressful condition. From a practical stand point, what we can see in a field condition is a symptom (something that happens due to a disease, is the visual effect of it when the disease is already established). The most common symtom is Leaf Curling, wilting, leaf rolling, plant withering. All of these symptoms are noticeable at different stages of the stress. 

Leaves curl in response to a hot and moisture deficient environment, why? so they can reduce their Active Photosynthetic Area or Active Surface Area so they don't lose too much water by transpiration. 

If transpiration continues after curling, the plant will close stomes. How to notice if that's happened? by touching the leaves, they feel warm and hot. Why? Because the water that's inside the venation in the xylem conducts is not moving anywhere and starts "boiling" inside the tissue. Also the water in the vacuoles gets hotter and hotter.

If the stress continues. As I mentioned before, that boiling water will "Cook" the leaf and the 1st cell group that dies is the one on the very tip of the leaf. So the process of "Die-Back" begins. 

There's no more water inside the vacuole organels and the cells begin to die. This process moves towars the stalk. 

It will usually begin in the middle to upper leaves. What's lower than that is mostly nutrient deficiency under stressful conditions. 

Reproductive structures that were forming stop their development and yield gets strongly reduced. If stressed during induction and key stages like "definition of number of kernels per row or number of rows of kernels" will reduce yields substantially. 

This is pretty much a Vague description of SOME of the things that happen when a plant is under water and temperature stress.

Thanks! 

 

Grain Yield

How do we define it ? How do we measure it ? What are the units ? 


Grain yield is more complex than what most of us think. We are used to hear "I got 180 bushels/acre of corn or 50 bushels/acre of soybeans" here in the U.S. 
In my homeland (Chile), they talk about "kilos/hectarea" or "quintals/hectarea". But what are the variables that will determine the yield ?


Let's define yield first; Yield means the productivity per unit of area. The Output, the Performance.
Is the amount of harvested plant parts that we get per any unit of area of cropland and or per plant (i.e. 40 pounds of pears/tree)
It is measured in Mass unit per Area unit. Corn is Quintals/hectarea (100 kg of grain per 10,000 square meters of cropland) or Bushels/acre (32 quarts or 63 pints of grain per 43,560 square feet of cropland).


The most important variable that will determine it at harvest is Moisture (%) or Water content, measured in %, meaning how many grams of water do we have in 100 grams of vegetal product. 


Yield is the consequence of three interactions: 

1. Environment
2. Genetics 
3. Agronomic Management

The environment includes the type of soil, pluviometry (rainfall), humidity, etc. The only predictible factor that will be present the next year will be the type of soil. All the others change during time and create either favorable or unfavorable conditions for pest and disease development. 


The genetics is basically the potential of a cultivar, variety, strain or hybrid of producing a maximum yield. It cannot be increased by any measure but it can be favored through good agronomics. 


Agronomic Management includes any practice such as irrigation, fertirrigation, application of fertilizers and additives (lime, strong acids, etc), cultural controls, etc. It can assist the yield by creating good conditions for the crop (soil-seed contact, seedbed, weed control, amongst others).

I hope this is helpful ! 

Know your Micro-Nutrients; how they work, get absorbed by the roots (uptake), are assimilated into the plant tissues, how to pinpoint a deficiency and its symptoms and what to do to correct a nutrient-lack situation. 

Before I start describing each and every micro-nutrient I'd like to remind you that every field is a different situation, that soil sampling is the first step in assessing and managing a farm and that if resources are available (time, money, equipment and know-how) compartmentalizing fields into homogeneous sections is ALWAYS recommended. The most important soil property that affects nutrient and mineral availability is pH (Figure 1).

If we look at the Figure 1, what can we get from it ? Ideal pH for most crops would be in the ''Very slightly acid" to the "Very slightly alkaline" or pH 6.5 - 7.5. In soils with low pH there will be a less availability of the most important nutrients (N, P, K, S, Ca, Mg, Mo) because they will be either bound to the soil coloids (Clay and Organic Matter) since the soluble forms (Soluble form is the form that the plants will uptake the elements) are positively charged or have been transformed into lose-able forms due to interactions with the Protons [H+] in the solution. . Furthermore, other Elements will be in a higher concentration (Fe, Mg, B, Cu, Zn) which can cause an adverse situation around the Rhizosphere, although those elements are needed by the plants, they need to be in extremely low concentrations. 

Management practices to correct such situation is the addition of a strong base like Lime Stone (CaCO3 or Calcium Carbonate). Another property to keep in mind while deciding whether to increase or decrease the pH of a soil is the Soil's Buffer Capacity, which is the measure (quantitative) of the resistance of the Soil solution to pH change when adding an Acid or a Base. 

• Sulfur (S): 
• Functions in plants: Essential for amino acid synthesis and protein formation. Necesarry for seed production, increase oil content in oilseed crops and promotes nodulation in legumes. 
• Form used by plants: SO4-- (Sulfate).
• Forms in the soil: Sulfate anion (SO4--), Element sulfur (S) and Organic sulfur (tied up to OM).
• Factors leading to its deficiency: Low OM, heavy texture soils, eroded soils, cold wet or poorly drained soils.
• Deficiency symptoms: Stunting, yellowing or chlorosis, newer tissue is yellower than older tissues, delayed maturity. Alfalfa and Corn are more affected by its deficiency due to they higher demand for this element. 

• Magnesium (Mg):
• Functions in plants: Actively involved in photosynthesis, forming the chlorophyll molecule. Involved in translocation of P in the plant. Regulates the uptake of other elements.
• Form used by plants: Mg++ (Exchangeable magnesium cation)
• Forms in the soil: Mg++, chemical compound as carbonates, oxides, bicarbonates, and silicates. Component of complex soil mineral structures.
• Soil factors leading to its deficiency: Acid sandy soils, excessive K fertilization.
• Deficiency symptoms: Interveinal chlorosis in the older to newer leaves. veins remain green. 

• Calcium (Ca)
• Functions in plants: Essential in Calcium Pectate (plant cell walls strenght), promotes root formation and leaf development, increases nodulation and bacterial activity in legumes, protein synthesis. 
• Form used by plants: Ca++ (Calcium cation)
• Forms in the soil: Ca++, chemical compound as carbonates, bicarbonates, oxides and silicates. 
• Soil factors leading to its deficiency: Acid soils (Strong acid range from Figure 1).
• Deficiency symptoms: Both root and shoot apex stunting, leaf tips can stick together and unfold abnormally. Younger growth can die back on the edges.q

• Zinc (Zn)
• Functions in plants: Essential for protein synthesis. Promotes seed and grain formation and plant maturity. Necessary for growth regulation and enzyme systems as a co-factor.
• Form used by plants: Zn++ (Exchangeable Zinc Cation)
• Forms in the soil: Zn++ held to clay coloids and OM, part of Zn mineral complexes.
• Soil factors leading to its deficiency: Low OM soils, sandy and eroded soils, high pH, calcerous soils (Zn will become less soluble as pH surpases 7,0). High P test levels, cold wet and poorly drained soils. Compation.
• Deficiency symptoms: General stunting by shortened internodes. Striped chlorosis (grasses) and mottling (broadleaves). Notorious in older young leaves as it is translocated to the newer growth. 

• Boron (B) 
• Functions in plants: Facilitates the transport of sugars through membranes, necessary for cell division and cell development, involved in plant utilization of N and P, including synthesis of nucleic acids and protein.
• Form used by plants: BO3--- (anion)
• Forms in the soil: H3BO3, H2BO3-, BO3---, B(OH)4-
• Soil factors leading to its deficiency: Precipitated on soil mineral surfaces, especially the micaceous clay minerals, Low B Test (Boiling Water Extraction), sandy, low organic matter soils that leach easily, soils in high rainfall climates, high pH, drought.
• Deficiency symptoms: Shortened internodes at the tip apix (rosette appearence).

• Iron (Fe)
• Functions in plants: Essential for chlorophyll formation, necessary for photosynthesis, part of enzyme system necessary for plant respiration, formation of some proteins.
• Form used by plants: Fe++ (cation).
• Forms in the soil: Fe++ (Ferrous) or Fe+++ (Ferric), insoluble oxides and hydroxides. 
• Soil factors leading to its deficiency: Excessive P, Ca, Zn, Mn, Cu can reduce Fe availability. pH greatly affects its availability.
• Deficiency symptoms: Stunting and spindly. Chlorosis of younger growth, veins remain green. Most notorious in Milo and Soybeans. 

• Manganese (Mn)
• Functions in plants: Essential for photosynthesis. Co-factor of several enzymes. Involved in nitrate assimilation. 
• Form used by plants: Mn++ (cation)
• Forms in the soil: Mn++
• Soil factors leading to its deficiency: Very sensitive to pH. Soluble and available in acid soils. Strong acid soils can have a Mn toxicity for the plants. 
• Deficiency symptoms: Yellowing between leaf veins, veins remain green (soybeans, edible beans, potatoes).

• Copper (Cu)
• Functions in plants: Essential in plant enzymes and protein synthesis. Promotes seed production. Important to chlorophyll formation. 
• Form used by plants: Cu++ (Cation)
• Forms in the soil: Cu+ (Cuprous cation) and Cu++ (Cupric cation). Adsorbed to clay mineral surfaces. Part of organic complexes. 
• Soil factors leading to its deficiency: Very high pH soils. High OM % (peat, mucks). Excessive Zn, Fe, or Mn may reduce its availability. Sandy soils.
• Deficiency symptoms: Small grains, leaf tips wilt, then die, looking like frost damage. Leaf tips stick together. Chlorosis and necrosis of youngest leaves.

• Molybdenum (Mo)
• Functions in plants: Required in legume nodule to fix N from atmosphere. Component of the enzyme in plants which causes Nitrate to be reduced to amino nitrogen, used in protein synthesis. 
• Form used by plants: MoO4-- (anion).
• Forms in the soil: MoO4-- (Molybdate) anion, pH 5-6 as HMoO4- anion. 
• Soil factors leading to its deficiency: low soil pH, solubility declines as pH icnreases. Very sandy soils, especially high weathered soils may be low in available Mo. 
• Deficiency symptoms: Poor nodule formation on legume roots. Pale green to yellow color of older leaves. Stunted plant growth. 

I hope you find this useful. I promise I will pin some pictures soon. 

Sure you know about Nitrogen ?

Nitrogen (N) 

What is it ? How does the plant use it ? How to calculate N units ? What are the management plans to use it ?

How can we figure out our crop's need for N ?

All of those questions and many more are just a stroke on this amazing subject. 

It can be found in the Atmosphere as N2 (Nitrogen), N2O (Nitrous Oxide), and many other gaseous forms. 

Will be available for plants after it's been fixed to the soil solution from the air by bacteria or industrially. 

The most common form of N in the soil is in the Organic Matter (OM) and is known as the Organic Nitrogen (ON).

ON has a chemical composition that makes it really resistant to any change on its structure which makes it unavailable for plant uptake. Altough it can be converted into Mineral Ammonium (Mineralization) by soil microbes. Subsequent to this it can be converted to Nitrate (Nitrification) by microbial activity. NO3- is the predominant form for plants to uptake it, but also the most mobile and most likely leachable form. 

Some of the processes that N is subjected to in the soil are described below

• Immobilization; Happens when there's a high C/N relation situation (high Carbon / low Nitrogen) in the corn stover or wheat chaff or any other crop leftover (usually grains). The available N in the soil will be used by bacteria in order to break down the fibers. It'll get tied up. It causes what's known as N Starvation. It is most likely to happen in no-till to reduced-till systems when the N is spread over the surface (that widens the N availability for the crop because its downward movement will depend on either irrigation or rainfall) and also because the stover accumulates on the surface over time. It is a temporary situation though so it doesn't affect the N rate in no-till or other tillage system. This explains why is is recommended to spread Urea (50 lbs/ac) right before incorporation of the residues after harvest. 
• Denitrification: Bacteria in saturated soils (with poor drainage due to compaction, or excessive rainfall, or field depressions where the water tends to stand) use the Oxygen from the Nitrate to breath causing the Nitrate to become into gaseous N (Unavailable for plant uptake and easily loseable). 
• Leaching: Excessive rainfall periods and poorly managed irrigation in soils with good drainage can cause this to happen. The NO3- does not bind with the soil particles (clays and OM have negative charges) and gets washed away from the root zone by the water as it infiltrates through the soil profile downward.
• Volatilization: Any form of N that converts into gaseous ammonia (NH3+) like Urea will be subjected to this process. Spinning spreaders are timely effective when it comes to put N on the ground, but no incorporation of it will drastically increase the volatilization. 

Liquid N form 30% and 32% at $320/ton and $342/ton, how much is an N Unit ?

1 ton are 2,000 lbs. 30% of 2,000 lbs are pure N so 30% are 600 lbs. So US$320/600 lbs = US$0,53/lbs

32% of 2,000 lbs so 32% are 640 lbs. US$342/640lbs = US$0,53/lb. 

That's how the N Units are calculated, why do we need to know that value ?

To make a N recommendation, which will be the most economical amount of nutrient to apply that returns its cost in a yield increase. 

Have a good week guys !