One of the major innovations of the Agricultural Revolution was the development of the Norfolk four-speed crop rotation, which greatly increased crop and livestock yields by improving soil fertility and reducing fallow land.
Crop rotation helped soils conserve specific nutrients for a variety of crops, allowing soil sustainability over time. Rather than using plots for the same crops each year, farmers began rotating their crops based on the nutritional needs of the crops grown each year.
New patterns of crop rotation and livestock paved the way for better crop yields, a greater variety of wheat and vegetables, and the ability to support more livestock. These changes affected society as the population became better nourished and healthier.
What is crop Rotation?
Crop rotation is the practice of planting different crops one after the other on the same plot to improve soil health, optimize soil nutrients, and control pest and weed pressure.
Suppose a farmer has planted a cornfield. When the corn harvest is over, he might plant beans because corn uses a lot of nitrogen and beans return nitrogen to the soil.
A simple crop rotation may involve two or three crops, and complex crop rotations may involve a dozen or more.
Why is crop rotation important in Agriculture?
Crop rotation helps return nutrients to the soil without synthetic additives. The practice also works to break pest and disease cycles, improve soil health by increasing biomass from the root structures of various plants, and increase biodiversity on the farm.
Increase Soil Organic Matter
Using different species in rotation allows for increased soil organic matter (SOM), better soil structure, and an improvement in the soil’s chemical and biological environment for plants.
With more SOM, water infiltration and retention improves, resulting in increased drought tolerance and less erosion.
Soil organic matter is a mixture of decaying biomass material with active microorganisms. Crop rotation inherently increases exposure to biomass from turf, green manure, and various other plant debris.
The reduced need for intensive tillage as part of crop rotation allows biomass aggregation to result in better nutrient retention and utilization, reducing the need for additional nutrients. In tillage, disturbance, and oxidation of the soil create a less favorable environment for the diversity and proliferation of microorganisms in the soil.
These microorganisms make nutrients available to plants. Thus, where “active” soil organic matter is a key to productive soil, soil with low microbial activity provides significantly fewer nutrients to plants; this is true even though the amount of biomass remaining in the soil may be the same.
Soil microorganisms also reduce the activity of pathogens and pests through competition. Also, plants produce root exudates and other chemicals that manipulate their soil environment as well as their weed environment. Thus, the rotation allows for increased yields from nutrient availability, but also alleviation of allelopathy and competitive weed environments
Increase Carbon Sequestration
Studies have shown that crop rotations greatly increase soil organic carbon (SOC), the main component of soil organic matter. Carbon, along with hydrogen and oxygen, is a macronutrient for plants.
Very different rotations over long time periods have been shown to be even more effective in increasing SOC, while soil disturbances (e.g. tillage) are responsible for the exponential decline in SOC values.
In Brazil, switching to no-till methods in combination with intensive crop rotations has shown a SOC sequestration rate of 0.41 tons per hectare per year.
In addition to increasing crop productivity, atmospheric carbon sequestration has major implications for reducing climate change rates by removing carbon dioxide from the air.
Studies have shown that crop rotations greatly increase soil organic carbon (SOC), the main component of soil organic matter. Carbon, along with hydrogen and oxygen, is a macronutrient for plants.
Very different rotations over long time periods have been shown to be even more effective in increasing SOC, while soil disturbances (e.g. tillage) are responsible for the exponential decline in SOC values.
In Brazil, switching to no-till methods in combination with intensive crop rotations has shown a SOC sequestration rate of 0.41 tons per hectare per year.
In addition to increasing crop productivity, atmospheric carbon sequestration has major implications for reducing climate change rates by removing carbon dioxide from the air.
Nitrogen-fixing
Crop rotation adds nutrients to the soil. For example, legumes, plants of the Fabaceae family, have nodules on their roots that contain nitrogen-fixing bacteria called rhizobia.
During a process called nodulation, the rhizobia bacteria use nutrients and water provided by the plant to convert atmospheric nitrogen into ammonia, which is then converted into an organic compound that the plant can use as a source of nitrogen.
It, therefore, makes agricultural sense to alternate them with cereals (Poaceae family) and other nitrate-requiring crops.
How much nitrogen is made available to plants depends on factors such as the type of legume, the effectiveness of rhizobia bacteria, soil conditions, and the availability of elements necessary for plant nutrition.
Pathogen and pest control
Crop rotation is also used to control pests and diseases that can become established in the soil over time. The rotation of crops in a row reduces the population level of pests by disrupting pest life cycles and disrupting pest habitats.
Plants within the same taxonomic family tend to have similar pests and pathogens. By regularly rotating crops and covering the soil with cover crops instead of fallow land, pest cycles can be interrupted or limited, especially cycles that benefit from overwintering in remnants.
For example, the root-knot nematode is a serious problem for some plants in warm climates and sandy soils, where it slowly accumulates to high concentrations in the soil and can seriously affect plant productivity by cutting off circulation to plant roots.
Growing a crop that is not a host for root-knot nematodes for one season will significantly reduce the concentration of nematodes in the soil, making it possible to grow a susceptible crop the following season without the need for soil fumigation.
This principle is particularly useful in organic farming, where pest control must be done without synthetic pesticides.
Weed management
The integration of certain crops, especially catch crops, in crop rotations is of particular value for weed control. These plants drive out weeds through competition.
In addition, sod and compost from cover crops and cover crops slow the growth of weeds while still being able to penetrate the soil, giving plants another competitive advantage.
By slowing the growth and spread of weeds while growing cover crops, growers reduce the presence of weeds for future crops, including shallow root and row crops, which are less resistant to weeds.
Cover crops are therefore regarded as conservation crops because they protect otherwise fallow areas from weed infestation.
This system has advantages over other common weed control methods, such as e.g. B. tillage. Tillage aims to inhibit the growth of weeds by turning the soil; however, this has the opposite effect, exposing weed seeds that may have been buried and burying valuable crop seeds. Crop rotation reduces the number of viable seeds in the soil by reducing the weed population.
In addition to their negative impact on crop quality and yield, weeds can slow down the harvesting process. Weeds make harvesting less efficient for farmers, as weeds like bindweed and knotweed can get caught in equipment, resulting in a kind of stop-and-go harvest.
Preventing soil erosion
Crop rotation can significantly reduce soil loss from water erosion. In areas highly prone to erosion, agricultural management practices such as zero and reduced tillage can be complemented with specific crop rotation methods to reduce the impact of raindrops, sediment detachment, sediment transport, surface runoff, and soil loss.
Protection against soil loss is maximized with rotation methods that leave the largest mass of crop stubble (plant debris left after harvest) on the soil.
Stubble covers in contact with the ground minimize water erosion by reducing the overland current velocity, current strength, and hence the water’s ability to detach and transport sediment.
Soil erosion and Cill prevent the disruption and detachment of soil aggregates that cause macropores to clog, infiltration to decrease, and runoff to increase. This significantly improves the resistance of soils to periods of erosion and stress.
Biodiversity
Increasing crop biodiversity has positive impacts on the surrounding ecosystem and can support a greater diversity of fauna, insects, and beneficial soil microorganisms as reported by McDaniel et al. 2014 and Lori et al. identified in 2017.
Some studies indicate increased nutrient availability from crop rotation under organic systems compared to conventional practices because organic practices are less likely to inhibit beneficial microbes in soil organic matter such as soil microbes.
Arbuscular mycorrhizae, which increases nutrient uptake in plants. Increasing biodiversity also increases the resilience of agro-ecological systems.
Farm productivity
Crop rotation contributes to higher yields through improved soil nutrition. By having to plant and harvest different crops at different times, more land can be farmed with the same amount of machinery and labor.