Farmers from ancient cultures such as Greece, China and Rome shared a common understanding with regards to crop rotations.
Through years of experience, they adopted the technique of crop rotation as they realized that growing the same crop year after year on the same land produced a minimal return and that it was possible to increase productivity dramatically throuh farming a series of crops over a number of seasons.
It slowly came to light how crop rotations in conjunction with green manures and cover crops, improved soil organic matter, tilth and fertility.
What is Crop Rotation?
Crop rotation can be defined as the practice of growing several dissimilar or different crop types in the same area in sequential seasons. Crop rotation is beneficial both to the environment and to the farmer.
The rationale behind crop rotation is when the same crop is grown at the same place for several years the soil is depleted of certain nutrients. By rotation, a crop that draws one particular kind of nutrient from the soil is followed during the consequent season by a crop that returns the nutrient to the soil or draws a distinct ratio of nutrients such as rice followed by cotton.
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'Managing your Nutrients' Certain Nutrients deplete so rotation helps maintain farming production. Image Credits: Photos.com
Choice of Crops
The sequence and choice of rotation crops is based on the nature of the soil, climate and precipitation, which when combined determines the plant type that may be cultivated. Other essential farming aspects such as economic variables and crop marketing must be considered when crop rotations are decided.
Two to six crop rotations may be done over a number of seasons. Multiple cropping systems such as companion planting or intercropping offer more complexity and diversity within the same rotation or season. Tomatoes can shade carrots and loosen the underlying soil. Double cropping is when two crops mostly of different species are sequentially grown in the same growing season.
Environmental Benefits of Crop Rotation
Nitrogen Management
While making nitrogen management decisions, it is very important to understand the relationship between crop rotation and nitrogen. Along with the other benefits of crop rotation, it may impact the rate of nitrogen mineralization or conversion of organic nitrogen to mineral nitrogen by modification of soil temperature, moisture, plant residue, pH and tillage practices.
Over the past 50 years, nitrogen has been used in large amounts especially to maximize farming production resulting in an increase in nitrogen within the soil profile of certain farms. Crop rotation plays a key role in reducing the risk of nitrate, leaching into surface and groundwater, by improving the availability of soil nitrogen and reducing the nitrogen fertilizer used.
Improved Soil Structure
Annual crop rotations cause a drastic difference in the root structure over a period of time. For crops having either tap or fibrous roots, the diversity in the root structure will enhance the chemical, physical and biological structure of the soil.
Soil improvement creates several macro pores and enables new root growth of subsequent crops. Improving soil organic matter and nutrient pools is also a benefit of crop rotation that results in better soil structure and increased water-holding capacity of the soil.
Reduced Soil Erosion
Improvement in soil tilth and microbial communities will help bring down soil erosion due to more stable soil structure, enhanced water infiltration and minimized surface runoff.
Improvement in Pest and Disease Control
The diversification of cropping sequences takes away the host organism and causes a disruption in the annual life cycle of insects, diseases and weeds. For instance, anthracnose and nematodes are susceptible to crop rotation. This results in better soil fertility and carbon storage.
Reduced Greenhouse Gas Emissions
By implementing crop rotation, the use of nitrogen fertilizer is drastically reduced considerably lowering greenhouse gas emissions. The global warming potential of nitrous oxide is much higher than that of carbon dioxide. Reduced synthetic fertilizer also means reduced greenhouse gas emissions from manufacture and transportation.
Reduced Water Pollution
By reducing the amount of synthetic fertilizers, water pollution caused by nitrogen will be considerably reduced. Diversified rotations with high share of crops and lesser dependence on pesticides bring down the use of pesticides as well as run off into groundwater.
Increased Ability to Store Carbon
Crop rotation practices can result in increased soil carbon content through high crop cover periods, reduced frequency and tillage intensity. Increase in the use of forages in crop rotations can result in better crop residue management while higher soil-carbon content helps combat climate change.
Green Manure Cover Crops
The main aim of planting green manure cover crops (GMCC) are for the purpose of providing nitrogen, cover and for smothering weeds. They are normally cut down before they reach maturity.
They can be planted as relay crops, inter crops or sole crops. The benefits of GMCCs are efficient weed control, additional biomass when no other crop can grow and nitrogen fixation in case leguminous crops are used. Different GMCCs have varied strengths in nitrogen fixation and weed control.
Conclusion
Crop rotation has a number of environmental benefits and is being widely considered in agriculture. It also has its risks such as less overall profitability because of decreased acreage of a highly valuable crop. Higher investment and low relative efficiency in machinery used for several crops is also an outcome.
Complicated rotations require more livestock and crop species. Hence the farmer may need added skills and make more time and equipment investments initially. In spite of these, crop rotation is highly beneficial and it is only required to determine the suitable rotation in order to benefit the sustainability and productivity of the farm.