UK agriculture has continuously been striving for higher yields and increased profitability for many decades. But time has shown that a profitable solution does not come in a bottle or a bag. Contrary to received wisdom, growing profitable crops is not solely related to yield! The cost of production in relation to yield is the greatest contributing factor to profit.
Farmers and growers have constantly grappled with factors beyond their control, from unpredictable weather patterns to market fluctuations. However, there’s a fundamental aspect of farming that can significantly impact income levels when properly understood and managed: soil health.
Welcome to the first instalment of our series dedicated to quantifying soil health in a way that’s not just about generating analytical data, but about helping farmers and growers increase the comprehension of their soil form and function to help maximise their profits.
The fundamental principle that this article attempts to explain is that a healthy soil generates a healthy crop, which in turn helps to generate a healthy profit.
Healthy soil = healthy crop = healthy profit.
It is important to remember the fundamental proportions that are contained within a healthy functioning ‘balanced’ soil. Because we can’t control the weather it is nearly impossible to always achieve a balanced soil as indicated below. But what we can do is create the environment that allows these balances between air and water to occur as often as possible and as a result nutritional exchange for a healthy plant is maximised, and so is the potential profit.
To create a balanced soil, we must start by knowing and understand the characteristics of the soil Texture Group, and work with it as best we can. Therefore, we need to know the mineral content which is the sand, silt, and clay fraction. We can’t fundamentally change these proportions, but our cultivation strategies can have a significant detrimental effect on profit due to granular segregation [1]. This is when the unproductive larger mineral elements (sand / chalk / stone) are brought to the surface, and the miniscule but highly productive silt and clay particles are lost through the soil profile never to return to the upper 75-100mm of soil where nutrient exchange takes place for the plants.
Granular segregation [1] [picture below] where unproductive lumps (of chalk, stone, boulders of clay) brought to the surface due to recreational ploughing – a repeated action just because ‘that is what we have always done’ Which is rarely appropriate treatment for the soil texture group.
Consider the impact granular segregation (in effect our cultivation strategies) will have on the soil constituent particle sizes (below) and nutritional availability:
In this soil health example, the soil texture group is a Sandy Silt Loam. Which contains 23% sand, 60% silt, and 17% clay.
- Sand only provides pore space and generally holds soil open to allow air and water ingress. It does not have a chemical charge (+ or -) and as such is inert.
- Conversely the miniscule silt and clay particles are negatively charged, and so retain the positively charged nutrients (cations) such as magnesium, copper, calcium in the rhizosphere for potential plant utilisation.
- In principle the greater the proportion of silt and clay in the sample, the greater the potential nutritional availability.
- In this example 77% of the soil can provide nutrition for plant growth.
Up until 2022 the Sandy Silt Loam had been ploughed every year for well over thirty years. This field was left fallow over winter as the soil had become saturated and unworkable.
Characteristics of a Sandy Silt Loam Soil:
- Moderately porous soil profile.
- Warms up quickly in the spring – depending on winter water saturation levels.
- Weak structure that is liable to cap, especially when overworked.
- Over working leads to surface ponding during rainfall, and a ‘tight’ soil structure that impedes root development as well as nutrient exchange.
- Excellent retention & release of water, providing organic matter levels are maintained.
Direct drilled on the left, Ploughed on the right.
2022
In the spring of 2022 half the field was ploughed and power-harrowed twice as in past years and drilled with spring oilseed rape on 5 April. The other half was drilled at the same time with a KUHN Espro 4000R direct-drill (DD).
- Prior to drilling / working the upper layers of soil had become extremely ‘tight’ due to the volume of rainwater, and as such it would have been advisable to lightly cultivate the soil before direct drilling to aid establishment. This wasn’t done, and consequently adversely affected the DD crop development.
- Spring oilseed rape was a poor choice of crop for this environment, as it is virtually impossible to stop Cabbage Stem Flea Beetle (CSFB) from decimating the crop. Which is exactly what happened.
- Weed control is also limited, and in a dry period following drilling, near impossible. The weather conspired to make this happen!
Within this comparison we must consider the cost of establishment. Figures taken from the Agricultural Business Costings (ABC) published May 2023.
As farmers are always short of both time and money, it is obvious to see the advantages of utilising a DD machine. I must stress that in this instance it would have been significantly beneficial to have used spring tine cultivators in the DD side to alleviate the tight soil surface.
In 2022, the ploughed side of the field cost nearly four times as much financially and took nearly six times longer to establish.
Visual observations from 28 April 2022:
- The ploughed half of the field had emerged a few days before the DD side. But so did a huge flush of weeds.
- The plants that emerged in the DD half looked significantly more robust, and initially were better able to withstand the continuous CSFB pressure. While the plants in the ploughed half were destroyed significantly faster by the CSFB. Presumably because they had a higher sugar content due to their more rapid growth.
- Interestingly the soil temperature in the DD half was 10C while in the ploughed side the temperature was 9.8C. The elevate temperature implies a better soil structure and function in the DD half of the field, which is logical.
- The ploughed soil had also slumped and desiccated, and a shovel had to be forced in to 150mm. [150mm is the crucial zone for nutrient exchange between root, microbes, and the soil] While in the DD side the spade eased into the same depth.
2023
Spring Oats were direct drilled into the whole field on 23 February 2023.
The average yield was a little over 5.0T/Ha. Not an unreasonable yield for the field.
Observations prior to harvest:
- The crop was lodged significantly in the side that was ploughed in 2022, As a result the combining rate had to be slowed thereby increasing costs.
- Though it didn’t show up on a photo, it was clearly apparent in the crop canopy exactly where the border between the two cultivation systems was in 2022.
- The crop that was year two of DD was stronger and significantly healthier than the ploughed side. Visibly less stem-based disease as well.
- A shovel easily penetrated the soil to 150mm in the second year of DD, but the same pressure only penetrated 75-100mm in the first year of DD after ploughing.
- The soil structure in the second year of DD was friable throughout the 150mm profile, while in the first year of DD after ploughing the soil was ‘blocky’ and had slumped together.
Soil analysis results and interpretation.
Unfortunately, to save costs individual samples were taken but from the same grid reference in both years. Samples will also be taken in the spring of 2024 for comparison.
| PPP 2022 | DD 2022 | DD 2022 | DD 2023 | |
| Total CEC meq/100g | 31.1 | 15.3 | 14.3 | 14.1 |
| OM Dumas % | 4.1 | 4.0 | 6.9 | 4.6 |
| Respiration mg/kg [2] | 148 | 177 | 89 | 154 |
| Carbon / Nitrogen ratio | 10.3 | 9.6 | 10.0 | 9.8 |
PPP = Plough press & power harrow
DD = Direct drilled
Comments on the chart above.
- Total CEC (Cation Exchange Capacity [3]) in the PPP 2022 significantly increases because of ploughing and is reflected in the short-term increase in nutritional availability. In effect ‘mining the soil’ as the microbes and worms are destroyed when soil is over cultivated. For the soil type, a CEC of 15 meq/100g would be the statistical norm.
- Organic matter variations in the DD years are likely an anomaly generated from only being able to take one sample.
- Consider that 1g of organic matter retains 0.8g of water.
- Also 1% organic matter retains 85,000 litres of water per hectare.
- Organic matter is a crucial component to ‘weatherproof’ your soils.
- The carbon to nitrogen reduction in the PPP side is indicative of the microbial degradation created by ploughing and power harrowing to create a fine seedbed. Conversely the DD side has remained consistent.
- The respiration (measure of total soil function, see [2] below) has increased in the PPP side by 29mg/kg, while the DD side has increased by a satisfying 65mg/kg.
- It will be fascinating to compare and contrast the 2022 & 2023 results with the proposed samples to be taken in 2024.
Ready to increase your farm’s profits through better soil health?
- Test your soil: Begin with a comprehensive soil analysis to understand its current condition.
- Save both time and money by consider practices such as reduced tillage and cover cropping to increase soil health, and ultimately profit.
- Consult independent experts that can provide advice and support to help with your soil’s evolution.
- Monitor progress: Track changes in crop yields and soil health.
Invest in your farm’s future by improving soil health today – get in touch with Lordington Park Agronomy for a free consultation.
References.
[1] Granular segregation – Granular materials tend to segregate. Segregation occurs due to small differences in either size or density when they flow or are shaken / vibrated = ploughed.
[2] Soil respiration is a measure of the carbon dioxide released from the soil by microbes decomposing soil organic matter and from the respiration of plant roots. Soil respiration indicates soil health (soil organic matter content, soil organic matter decomposition and the level of microbial activity).
[3] Cation Exchange Capacity (CEC) is a measure of how many cations can be retained on soil particle surfaces. Negative charges on the surfaces of soil particles bind positively-charged atoms or molecules (cations e.g., calcium; potassium; magnesium), but allow these to exchange with other positively charged particles in the surrounding soil water, so that roots can absorb the nutrients by osmosis.