There are 7 critical points for influencing yield in any farming system. Hitting each of these points will maximise our yield by preventing any yield loss.
The 7 critical points for influencing yield are:
- Seed
- Head Determination
- Photosynthetic Ability
- Flowering
- Cell Division
- Grain Fill
- Ripening
In this article, we’ll discuss each of these stages and the critical nutrients required for each stage. We have also included when you should sap test and wehn to foliar apply in order to achieve maximium yields.
But first, make sure to watch the video below from our YouTube channel (Agriculture Explained) explaining this topic (And subscribe).
Get access to our Critical Points Of Influence Guide For Wheat
Yield Is Never Gained, only lost
A very important concept to understand with the critical points of influencing yield is that yield is only ever lost when nutritional deficiencies or stress is applied to the crop. This implies that the seed has 100% of the potential yield, however, if for example Calcium is below the required amount during a critical stage, or water is in little supply, our potential yield reduces and reduces until we arrive at our actual yield.
Therefore, as farmers, we must be able to supply the crop exactly what the crop needs at exactly the right timing. At agresol, we do this through Differential Sap Testing and applying foliars before each critical point of influence.
As seen below, potential yield is the limit of the crop, however with limitions such as water or nutritional limitations, yield is reduced to actual yield.
1 - Seed Quality
The seed stage is a critical point in a crop’s life cycle, where the foundations for plant health and productivity are set in motion. Despite appearing dormant, the seed is undergoing significant biological activity, and the right nutrient support at this time can influence everything from root development to long-term crop resilience.
What’s Happening Biologically at the Seed Stage?
As soon as a seed is hydrated and activated, it begins metabolising stored energy reserves to initiate germination. This stage doesn’t rely on photosynthesis yet — instead, everything the plant needs must be drawn from its internal reserves or the immediate environment.
A key process that begins almost immediately is cell division. The rate and quality of cell division at this early stage determine how efficiently the seedling will develop its roots, shoots, and leaves. Healthy, well-formed cells are more resilient, more metabolically active, and better at accessing and utilising nutrients.
Why Is Nutrition So Important Now?
At this stage, the plant is building its structural blueprint. If nutrient deficiencies occur during cell division, those flaws can’t be undone later — they become embedded in the plant’s architecture.
Crucially, the seed stage sets up:
Root architecture (which governs future nutrient and water uptake)
Shoot emergence and early leaf development
The strength of microbial associations in the rhizosphere
Genetic expression that influences disease resistance and yield potential
Key Nutrients for the Seed Stage
To support proper germination and the first wave of cell division, the plant needs a targeted suite of nutrients:
Phosphorus (P): Supports energy transfer via ATP and is essential for strong root development. Low phosphorus availability can delay emergence and reduce vigour.
Calcium (Ca): Required for cell wall integrity and cell division. Calcium is immobile within the plant, so early availability in the root zone is crucial to build strong, healthy cells from the start.
Zinc (Zn): Vital for hormone production and enzyme function. It influences growth hormones like auxin that help guide root and shoot directionality.
Manganese (Mn): Supports enzyme activity during early root initiation and protects against oxidative stress.
Cobalt (Co): Often overlooked, cobalt supports the production of vitamin B12 analogues and is important for nitrogen-fixing microbes that will colonise the root zone.
Supporting the Rhizosphere Early
Early microbial relationships form during the seed stage, even before full root systems develop. If conditions support microbial life (moisture, warmth, and root exudates), beneficial fungi and bacteria will begin to colonise the seed’s rhizosphere.
Encouraging microbial activity at this stage helps with:
Enhanced nutrient solubilisation (especially phosphorus and trace elements)
Biological nitrogen fixation (via early rhizobial associations in legumes)
Early disease suppression by competitive exclusion of pathogens
Microbial inoculants, compost teas, or seed coatings can offer big benefits here — particularly when paired with a carbon source like molasses or humic acids to feed beneficial populations.
Best Practices for Farmers
Start with a high-quality seed that’s been tested for germination rate and free from seed-borne diseases. Larger seed weight has been linked with greater seedling vigor and potentially greater yield.
- Source Seed From Regenerative Farmers. These seeds are likely to have a strong and intact microbiome, assisting the plant in developing a strong rhizosphere.
Use microbial inoculants at planting — either directly on the seed or in-furrow — to kickstart rhizosphere biology.
Apply Nutrition As a Seed Treatment, this provides the plant and microbes with direct access to minerals that could be missing.
Consider humic substances or kelp extracts to chelate nutrients and stimulate root hormones.
Avoid high-salt fertilisers or excess nitrogen at this stage — they can damage emerging roots and suppress microbial life.
Learn more about our recommended seed treatment in our article Regenerative Seed Treatments.
Outcomes of Good Nutrition at the Seed Stage
Faster, more uniform germination
Stronger root systems
Increased microbial colonisation
Improved resilience to early stressors (drought, pathogens, compaction)
Better nutrient use efficiency throughout the plant’s life
Important Nutritent Interactions
It is very important we understand how nutrients interact for us to manage the crop’s nutrition, as the excess of one nutritent can reduce or increase the uptake of another. The three important nutrient interactions for manageing the critial points of infleuce are:
Calcium + Boron: Boron is required for the uptake of Calcium. Without boron, calcium can be deficient in the crop while being sufficient in the soil.
Calcium – Potassium: Since both of these are cations, they share similar uptake pathways, when potassium is in excess, calcium uptake is reduced.
Potassium -/+ Manganese: Manganese is required to regulate potassium. Often an excess or deficiency of potassium is simply due to a manganese deficiency.
There are many other important nutrient interactions as you can see below in Mulders Chart Of Nutrient Interactions, however the above are the key nutrients to manage for critical points of influencing yield.
2 – Head Determination
The head determination stage is one of the most critical, yet often underappreciated phases in a crop’s development. It typically occurs after a few weeks from germination, in seed it occurs around the Z13 stage, this is long before flowering. During this time, the plant is not visibly reproductive, but internally, it is deciding how many seed heads to form, how many spikelets per head, and how grains per spikelet.
Yield potential is set, not filled during this stage — meaning nutrient decisions made here have a direct influence on final productivity.
What Happens Biologically During Head Determination
At this stage, the growing point (meristem) transitions from producing leaves to producing floral structures. In cereals and grasses, this is when tillers are determined and head primordia are initiated. In broadacre crops like canola or sunflower, it’s the stage when flower sites and branching architecture are locked in.
This transition is regulated by plant hormones, sugars, and nutrient availability, particularly:
Cytokinins (promote cell division and flowering)
Auxins (guide apical dominance and branching)
Gibberellins (support elongation and flowering)
Sugar signalling (sufficient sugar reserves confirm the plant can afford to reproduce)
Below is the development of the meristem between crop stages Z10 and Z20, this is exactly where this critical point of influence on yield occurs.
Key Nutrients for the Head Determination Stage
Calcium (Ca): Required for Cell Division and promotes cytokinin production.
Manganese (Mn): Mn is very important as it regulates potassium uptake. This therefore, prevents potassium from antgoniseing calcium.
Boron (B): Increases Ca uptake.
Zinc (Zn): Regulates growth hormones and internode elongation, Supports early floral meristem development and Needed for the synthesis of auxins, which shape head size and seed set.
Copper (Cu): Builds lignin for structural support of reproductive organs.
Urea (N): Depending on the crop and the results from the sap test, a small amount of Urea can be benefitical for increasing tiller production.
Kelp: We like to add kelp to the mix as it contains large amounts of cytokinins which stimulants cell division in the plant.
Why This Stage Is So Influential
Once the plant has determined how many seed heads and flowers to produce, it cannot add more later — only lose them under stress. That makes this stage a ceiling for your yield potential. Ensuring adequate nutrition now is an investment in grain number rather than just grain size or fill later on.
In essence:
More heads = higher yield ceiling
Well-nourished flowers = better pollination and seed fill
Balanced micronutrients = less floral abortion and blanking
Tips for Supporting This Stage on Farm
- Nutrition Via Seed treatment or Starter: Because the crop at this stage is very small, a foliar application is not effective due to limited leaf area, therefore we need to consider getting the nutritents needed into the crop from the seed treatment or starter fertiliser.
Foliar feed: We can still foliar apply minerals towards the later stage with with a mix of the minerals above, but a sap test should be taken first.
Sap test before this stage to identify deficiencies early — corrections made after head determination are often too late.
Reduce stressors like herbicide pressure, compaction, or waterlogging that interfere with hormonal signalling.
Avoid over-applying nitrogen here — too much can delay flowering or skew energy towards vegetative growth, this is espically true of nitrate forms of N.
What You Can Expect With Proper Management
More uniform flowering
Increased seed head and flower site numbers
Improved pollen viability and fertilisation
Higher grain numbers per plant
Greater resilience against environmental stress during flowering
3 - Photosynthetic Ability
Photosynthesis is the engine of crop production, meaning that is it critical to maximise solar capture and conversion efficiency to grow and develop the crop. This is the Photosynthetic Ability Stage, where the plant’s capacity to convert sunlight into sugars will determine how well it can fill grain, grow biomass, and support biological interactions in the rhizosphere.
This stage doesn’t correspond to a single growth phase — it runs parallel with reproductive development (from pre-flowering to mid grain-fill), and its effectiveness directly influences final yield outcomes.
The development of a strong flag leaf is also very important during this stage as it provides 40-50% of the carbohydrates during grain fill.
Why Photosynthetic Capacity Matters
Photosynthesis powers:
Sugar production for grain fill
Root exudation, which feeds soil biology and improves nutrient availability
Energy for flowering, pollination, and protein synthesis
Hormone production, including those regulating grain set and plant resilience
When photosynthetic rates drop — due to nutrient deficiency, heat stress, or disease — the plant is less able to fill grain, support microbial partners, or complete reproductive development.
The Three Components to the Photosynthetic stage
- Increasing Photosynthesis
- Reducing Pest and Disease with complent protein synthesis
- Stimulanting quality vegetative growth
Increasing Photosynthesis
To increase photosynthesis, you’ll need to make sure the crop has sufficient levels of these nutrients:
Nitrogen (N): This is important in building chlorophyll (as you can see below), as well as other components in the plant.
Magnesium (Mg): Also very important in the chlorophyll. It forms the center peice for capturing light.
Manganese (Mn): Required in the oxygen evolving complex which splits water into oxygen and hydrogen.
Iron (Fe): Required in the building of chlorophyll and carotenoids which extend the ability of the plant to capture light.
Phosphorous (P): Required in ATP which acts like a battery in the cell.
Protein Synthesis
In order to reduce pest and disease, N in the sap needs to be converted into complete proteins, this can be done with sufficient levels of the following minerals:
Sulfur: Required in the amino acids methionine and cystine. methionine is very important as it is the first amino acid in every protein.
Magnesium (Mg): Mg is required in the ribosome, which build poly-peptide chains which get turned into proteins.
Boron (B): Not used in protein synthesis, but it is important for translocating N and sugars around the plant, hence preventing buildup.
Molybdenum (Mo): Required in Nitrate Reductase enzyme which converts nitrate into nitrite.
Nickel (Ni): Required in the enzyme Urease, which converts urea into ammonia.
Quality Vegetative Growth
It is important to get a robust plant frame which allows for large amounts of leaves and grain weight. However, vegetative growth is usually triggered by auxin production, of which is stimulated by nitrate. This can be a problem as nitrate creates a dilution effect on all other minerals as the plant rapidly grows but doesn’t have enough of the other minerals to support quality growth. Instead, the following minerals can achieve similar growth but of higher quality.
Calcium (Ca): Ca provides strong cell walls and cytokinin production while stimulanting quality vegetative growth.
Boron (B): B assists in Ca uptake.
Silicon (Si): Also helps to build strong cell walls and helps the plant resist biotic and abiotic stress.
This mix also improves the plant’s resistance to pest and disease, you can find out more in our video Three Minerals For Plant Defence
Bonus Mineral – Zinc: Zinc regulates leaf size, therefore making sure our plants have enough Zn can increase plant leaf size and therefore allow them to capture more light.
John Kempf’s Plant Health Pyramid
To learn more about how mineral nutrition is important for plant defence against pest and disease, check out our article dicussessing John kempf’s Plant Health Pyramid
Controling Cereal Rust With ZERO Chemicals
Likewise, check out the article Controling Cereal Rust With ZERO Chemicals to learn how you can protect your plant with less chemcial usage, this is important as it protect the flag leaf, allowing the leaf to photosynthesis more.
4 - Flowering
The flowering stage is one of the most critical and sensitive periods in a plant’s life. It’s the point where vegetative growth transitions to reproduction — the plant’s genetic legacy depends on successful pollination and seed set. It’s also the period where stress, nutrient imbalances, or biological disruptions can cause irreversible yield loss.
For cereal crops, flowering (anthesis) often occurs shortly after head emergence. For legumes and broadleaf species, flowering can extend over a longer window. Regardless of crop type, this stage demands precise management to ensure a high grain/seed set, strong hormone signalling, and stress protection.
Why Flowering is a Make-or-Break Moment
During flowering, the plant is:
Forming reproductive organs (stamens, ovaries, pollen)
Engaging in pollination and fertilisation
Shifting energy resources from roots and leaves into flowers
Highly sensitive to stress — heat, drought, or nutrient limitations can abort flowers or reduce pollen viability
Yield potential is directly tied to how many flowers are successfully fertilised and retained. Missing the right support here limits how much grain the plant can actually fill later.
Nutrient Requirements at Flowering
Calcium (Ca): Crucial for cell division and stability of reproductive organs.
Manganese (Mn): Mn is very important as it regulates potassium uptake. This therefore, prevents potassium from antgoniseing calcium.
Boron (B): Important for Ca uptake.
Zinc (Zn): Regulates growth hormones and internode elongation, Supports early floral meristem development and Needed for the synthesis of auxins, which shape head size and seed set.
Copper (Cu): Builds lignin for structural support of reproductive organs.
Kelp: We like to add kelp to the mix as it contains large amounts of cytokinins which stimulants cell division in the plant.
Phosphorus (P): Needed for energy transfer (ATP) and pollen development.
Outcomes You’re Aiming For
High percentage of flowers setting viable grain or seed
Balanced energy flow between roots and reproductive organs
Improved pollen viability and fertilisation success
Strong hormonal resilience to weather or nutrient stress
More even maturity and better grain uniformity at harvest
5 - Cell Division
Once pollination and fertilisation occur, the crop enters a vital developmental phase driven by rapid cell division. This stage is often invisible to the eye, but it’s where seed potential is locked in — the number of cells formed now determines the capacity for future grain or fruit size.
This early post-pollination phase is not about “filling” the grain yet — it’s about building the internal architecture that will later hold proteins, oils, starches, and minerals.
What is Happening Biologically?
Each fertilised ovule begins intense cell division in both the endosperm (food storage tissue) and the embryo (future plant).
These new cells set the framework for seed size and function.
The rate and duration of cell division depend on temperature, hormonal signals, and nutrient availability.
If stress occurs now (e.g. heat, drought, or a lack of calcium or boron), the plant limits cell division, resulting in smaller grains or reduced seed viability.
This stage happens immediately after fertilisation and occurs for 10-14 days.
Nutrient Requirements For Cell Division
Manganese (Mn): Mn is very important as it regulates potassium uptake. This therefore, prevents potassium from antgoniseing calcium.
Calcium (Ca): Crucial for cell division and stability of reproductive organs.
Boron (B): Important for Ca uptake.
Potassium (K) – Not required but rather make sure it’s NOT supplied! This will reduce calcium and therefore reduce cell division.
Kelp: We like to add kelp to the mix as it contains large amounts of cytokinins which stimulants cell division in the plant.
6 -grain Fill
Once the crop has passed pollination and completed its cell division phase, it moves into grain fill — the stage where those newly formed cells are now filled with carbohydrates, proteins, oils, and minerals. This stage is the culmination of all previous growth and often determines the final yield and quality of the crop.
In regenerative farming, grain fill is seen as not just a passive “storage” process but a reflection of plant health, nutrient cycling, and microbial symbiosis.
Ensuring we have a good grain fill period is very important for maximising the grain weight and can have massive effects of the 1000 grain test weight
What Is Happening Biologically?
Starch, protein, and lipid synthesis ramps up within the seed.
Sugars from photosynthesis are converted into complex storage compounds, primarily in the endosperm.
Minerals are translocated to support enzyme activity and seed nutrition.
This is an energy-intensive phase, and stress can halt filling or trigger premature senescence.
Nutrient Needs During Grain Fill
Potassium (K): The system not switches to require large amounts of K. K regulates water movement and turgor pressure, enabling sugars to flow into the grain. It is also critical for enzyme activity during starch synthesis.
Nitrogen (N): Key for protein synthesis and increasing protein content in the grain. Urea is a good option, amino acids is also a good option but more expensive.
Manganese (Mn): Mn is very important as it regulates potassium uptake, this is important as we want to maximise the amount of K during this stage.
Zinc (Zn): Involved in starch formation and hormone balance. Deficiency can lead to shrivelled grains or seeds lacking vigour.
Boron (B): Boron is important to translocate the carbohydrates into the grain.
Calcium (Ca): Still important for mantaining the cell wall strength during this stage. Don’t over apply as this will affect K.
Copper (Cu):Copper is crucial for enzyme activity and nutrient translocation to the developing seeds
Kelp: Help to assist in cell elongation.
6 - Ripening
The ripening stage is the final chapter in the crop’s lifecycle. While it may appear that the crop is simply “drying down,” a lot is still happening internally. During this phase, the plant completes nutrient transport, starch hardening, and grain desiccation, all of which are critical to yield, grain quality, and storability.
It is important because we can still influence this stage using nutrition to prolong or shorten ripening, either allowing for a earlier harvest or extended grainfill which increases grain weight.
Nutrient Needs During Ripening
Boron (B): B will shortern the ripening stage allowing for an early harvest. This occurs as carbohydrates more faster into the grain, increasing ethylene production and triggering senescence sooner.
Or
Cobalt (Co): Co stimulants cytokinins production which inhibits Ethylene, this prolongs senescence from occuring for up to a week. This means more carbohydrates can be moved into the grain.
S, Mg, Mo, Ni: During this stage we also want to make sure N is converted into proteins so applying the protein synthesis minerals can assist with that convertion.
Maintaining Good Levels of Calcium
As you may have noticed, Calcium is very important for almost all critical points of influence, therefore a continuous supply of calcium is important. This can be achieved by stimulanting the rhizophagy cycle which allows microbes to supply the crop with nutrition. For more information on the rhizophagy cycle, check out our article called Dr Jame White’s Rhizophagy Cycle.
This can be stimulanted with good soil health practices as well as applying microbes to the seed coat or applying a soil primer.
Maximise Your Yields With Regenerative Agriculture
If maximising your yields using precise nutrition and microbial management is something you would like to implement on your farm, get in contact with the team at Agresol. We offer a FREE consultation for anyone wanting to get started in regenerative agriculture, so use the buttom below to get started.
