The term cropping system refers to the crops, crop sequences and management techniques used on a particular agricultural field over a period of years. It includes all spatial and temporal aspects of managing an agricultural system. Historically, cropping systems have been designed to maximise yield, but modern agriculture is increasingly concerned with promoting environmental sustainability in cropping systems. [1]
Crop choice is central to any cropping system. In evaluating whether a given crop will be planted, a farmer must consider its profitability, adaptability to changing conditions, resistance to disease, and requirement for specific technologies during growth or harvesting. [2] They must also consider the prevailing environmental conditions on their farm, and how the crop will fit in with other elements of their production system. [2]
Monoculture is the practice of growing a single crop in a given area, where polyculture involves growing multiple crops in an area. Monocropping (or continuous monoculture) is a system in which the same crop is grown in the same area for a number of growing seasons. Many modern farms are made up of a number of fields, which can be cultivated separately and thus can be used in a crop rotation sequence. Crop rotation has been employed for thousands of years and has been widely found to increase yield and prevent harmful changes to the soil environment that limit productivity in the long term. [3] Although the specific mechanisms regulating that effect are not fully understood, [4] they are thought to be related to differential effects on soil chemical, physical, and microbiological properties by different crops. [5] By affecting the soil in different ways, crops in a rotation help to stabilise changes in the properties. Another consideration is that many agricultural pests are species-specific and so having a given species present in a field only some of the time helps to prevent populations of pests from growing. [6]
The organisation of individual plants in a field is also variable and typically depends on the crop being grown. Many vegetables, cereals, and fruits are grown in contiguous rows, which are wide enough to allow cultivation (or mowing, in the case of fruits) without damaging crop plants. Other systems aim for maximum plant density and have no such organisation. Forages are grown in that manner since animal traffic is expected, and maximum plant density is required for their nutrition, as are cover crops, since their purpose of competing with weeds and preventing soil erosion depends largely on density. [7]
Managing crop residues is important in most systems. Some of the nutrients contained in these dead tissues are made available to crops during decomposition, [8] reducing the need for fertiliser inputs. Leaving residues in place also increases the soil organic matter (SOM), which has a number of benefits. [9] Specific management practices can have a number of other impacts.
Tillage is the primary method by which farmers manage crop residues. Different types of tillage result in varying amounts of crop residue being incorporated into the soil profile. Conventional or intensive tillage typically leaves less than 15% of crop residues on a field, reduced tillage leaves 15–30%, and conservation tillage systems leave at least 30% on the soil surface. [10] The differences observed across these systems are diverse, and there is still considerable debate concerning their relative economic and environmental impact, but a number of widely reported benefits have led to a major shift towards reduced tillage in modern cropping systems. [11]
In general, leaving residues on the soil surface results in a mulching effect which helps control erosion, [12] prevents excessive evaporation, and suppresses weeds, [13] but may necessitate the use of specialised planting equipment. [14] Incorporating residues into the soil profile results in rapid decomposition by soil microorganisms, [15] which makes planting easier and in some cases could mean that nutrients will be made available to plants sooner, but limited erosion control and weed suppression are provided.
Under reduced or no-tillage, limited exposure to soil microorganisms can slow the rate of decomposition thus delaying the conversion of organic polymers to carbon dioxide and increasing the amount of carbon sequestered by the system, [16] [17] [18] although in poorly aerated soils this may be offset in part by an increase in nitrous oxide emissions. [19]
In some systems residues are burned. This is a fast and cheap way to clear a field in preparation for the next planting, and can assist with pest control, but has a number of drawbacks: organic matter (carbon) is lost from the system, soil is exposed and becomes more susceptible to erosion, and the smoke produced is an atmospheric pollutant. [20] In many parts of the world, this practice is restricted or banned. [21]
Especially in developing countries, crop residues may be removed and used for human or animal consumption, or other purposes. [22] This provides a secondary source of sustenance or income, but precludes the benefits associated with leaving residues within the system.
Nutrients are depleted during crop growth, and must be renewed or replaced in order for agriculture to continue on a piece of land. This is generally accomplished with fertilisers, which can be organic or synthetic in origin. A large component of the organic farming movement is a preference for organic-source fertilisers.
Excessive fertilisation is not only costly, but can harm crops and have a number of environmental consequences. [23] Therefore, there is considerable interest in developing nutrient management plans for individual plots which attempt to optimise fertiliser application rates.
Soil moisture content is an important factor in plant development, and must be maintained within a range throughout the growing period. The range of tolerable moisture conditions varies from crop to crop. Irrigation and fine-textured amendments can be used to increase soil moisture, whereas coarser-textured amendments and technologies such as tile drainage can be used to decrease it. [24] [25]
Tillage is the agricultural preparation of soil by mechanical agitation of various types, such as digging, stirring, and overturning. Examples of human-powered tilling methods using hand tools include shoveling, picking, mattock work, hoeing, and raking. Examples of draft-animal-powered or mechanized work include ploughing, rototilling, rolling with cultipackers or other rollers, harrowing, and cultivating with cultivator shanks (teeth).
Crop rotation is the practice of growing a series of different types of crops in the same area across a sequence of growing seasons. This practice reduces the reliance of crops on one set of nutrients, pest and weed pressure, along with the probability of developing resistant pests and weeds.
Conservation agriculture (CA) can be defined by a statement given by the Food and Agriculture Organization of the United Nations as "Conservation Agriculture (CA) is a farming system that can prevent losses of arable land while regenerating degraded lands.It promotes minimum soil disturbance, maintenance of a permanent soil cover, and diversification of plant species. It enhances biodiversity and natural biological processes above and below the ground surface, which contribute to increased water and nutrient use efficiency and to improved and sustained crop production."
In agriculture, a green manure is a crop specifically cultivated to be incorporated into the soil while still green. Typically, the green manure's biomass is incorporated with a plow or disk, as is often done with (brown) manure. The primary goal is to add organic matter to the soil for its benefits. Green manuring is often used with legume crops to add nitrogen to the soil for following crops, especially in organic farming, but is also used in conventional farming.
In agriculture, cover crops are plants that are planted to cover the soil rather than for the purpose of being harvested. Cover crops manage soil erosion, soil fertility, soil quality, water, weeds, pests, diseases, biodiversity and wildlife in an agroecosystem—an ecological system managed and shaped by humans. Cover crops can increase microbial activity in the soil, which has a positive effect on nitrogen availability, nitrogen uptake in target crops, and crop yields. Cover crops reduce water pollution risks and remove CO2 from the atmosphere .Cover crops may be an off-season crop planted after harvesting the cash crop. Cover crops are nurse crops in that they increase the survival of the main crop being harvested, and are often grown over the winter. In the United States, cover cropping may cost as much as $35 per acre.
A mulch is a layer of material applied to the surface of soil. Reasons for applying mulch include conservation of soil moisture, improving fertility and health of the soil, reducing weed growth, and enhancing the visual appeal of the area.
In agriculture, polyculture is the practice of growing more than one crop species together in the same place at the same time, in contrast to monoculture, which had become the dominant approach in developed countries by 1950. Traditional examples include the intercropping of the Three Sisters, namely maize, beans, and squashes, by indigenous peoples of Central and North America, the rice-fish systems of Asia, and the complex mixed cropping systems of Nigeria.
Topsoil is the upper layer of soil. It has the highest concentration of organic matter and microorganisms and is where most of the Earth's biological soil activity occurs.
No-till farming is an agricultural technique for growing crops or pasture without disturbing the soil through tillage. No-till farming decreases the amount of soil erosion tillage causes in certain soils, especially in sandy and dry soils on sloping terrain. Other possible benefits include an increase in the amount of water that infiltrates into the soil, soil retention of organic matter, and nutrient cycling. These methods may increase the amount and variety of life in and on the soil. While conventional no-tillage systems use herbicides to control weeds, organic systems use a combination of strategies, such as planting cover crops as mulch to suppress weeds.
Tilth is a physical condition of soil, especially in relation to its suitability for planting or growing a crop. Factors that determine tilth include the formation and stability of aggregated soil particles, moisture content, degree of aeration, soil biota, rate of water infiltration and drainage. Tilth can change rapidly, depending on environmental factors such as changes in moisture, tillage and soil amendments. The objective of tillage is to improve tilth, thereby increasing crop production; in the long term, however, conventional tillage, especially plowing, often has the opposite effect, causing the soil carbon sponge to oxidize, break down and become compacted.
Organic fertilizers are fertilizers that are naturally produced. Fertilizers are materials that can be added to soil or plants, in order to provide nutrients and sustain growth. Typical organic fertilizers include all animal waste including meat processing waste, manure, slurry, and guano; plus plant based fertilizers such as compost; and biosolids. Inorganic "organic fertilizers" include minerals and ash. The organic-mess refers to the Principles of Organic Agriculture, which determines whether a fertilizer can be used for commercial organic agriculture, not whether the fertilizer consists of organic compounds.
In agriculture, a living mulch is a cover crop interplanted or undersown with a main crop, and intended to serve the purposes of a mulch, such as weed suppression and regulation of soil temperature. Living mulches grow for a long time with the main crops, whereas cover crops are incorporated into the soil or killed with herbicides.
Agricultural soil science is a branch of soil science that deals with the study of edaphic conditions as they relate to the production of food and fiber. In this context, it is also a constituent of the field of agronomy and is thus also described as soil agronomy.
Strip-till is a conservation system that uses a minimum tillage. It combines the soil drying and warming benefits of conventional tillage with the soil-protecting advantages of no-till by disturbing only the portion of the soil that is to contain the seed row. This type of tillage is performed with special equipment and can require the farmer to make multiple trips, depending on the strip-till implement used, and field conditions. Each row that has been strip-tilled is usually about eight to ten inches wide.
The environmental impact of agriculture is the effect that different farming practices have on the ecosystems around them, and how those effects can be traced back to those practices. The environmental impact of agriculture varies widely based on practices employed by farmers and by the scale of practice. Farming communities that try to reduce environmental impacts through modifying their practices will adopt sustainable agriculture practices. The negative impact of agriculture is an old issue that remains a concern even as experts design innovative means to reduce destruction and enhance eco-efficiency. Animal agriculture practices tend to be more environmentally destructive than agricultural practices focused on fruits, vegetables and other biomass. The emissions of ammonia from cattle waste continue to raise concerns over environmental pollution.
Soil management is the application of operations, practices, and treatments to protect soil and enhance its performance. It includes soil conservation, soil amendment, and optimal soil health. In agriculture, some amount of soil management is needed both in nonorganic and organic types to prevent agricultural land from becoming poorly productive over decades. Organic farming in particular emphasizes optimal soil management, because it uses soil health as the exclusive or nearly exclusive source of its fertilization and pest control.
Natural farming, also referred to as "the Fukuoka Method", "the natural way of farming", or "do-nothing farming", is an ecological farming approach established by Masanobu Fukuoka (1913–2008). Fukuoka, a Japanese farmer and philosopher, introduced the term in his 1975 book The One-Straw Revolution. The title refers not to lack of effort, but to the avoidance of manufactured inputs and equipment. Natural farming is related to fertility farming, organic farming, sustainable agriculture, agroecology, agroforestry, ecoagriculture and permaculture, but should be distinguished from biodynamic agriculture.
Regenerative agriculture is a conservation and rehabilitation approach to food and farming systems. It focuses on topsoil regeneration, increasing biodiversity, improving the water cycle, enhancing ecosystem services, supporting biosequestration, increasing resilience to climate change, and strengthening the health and vitality of farm soil.
Soil regeneration, as a particular form of ecological regeneration within the field of restoration ecology, is creating new soil and rejuvenating soil health by: minimizing the loss of topsoil, retaining more carbon than is depleted, boosting biodiversity, and maintaining proper water and nutrient cycling. This has many benefits, such as: soil sequestration of carbon in response to a growing threat of climate change, a reduced risk of soil erosion, and increased overall soil resilience.
Carbon farming is a set of agricultural methods that aim to store carbon in the soil, crop roots, wood and leaves. The technical term for this is carbon sequestration. The overall goal of carbon farming is to create a net loss of carbon from the atmosphere. This is done by increasing the rate at which carbon is sequestered into soil and plant material. One option is to increase the soil's organic matter content. This can also aid plant growth, improve soil water retention capacity and reduce fertilizer use. Sustainable forest management is another tool that is used in carbon farming. Carbon farming is one component of climate-smart agriculture. It is also one way to remove carbon dioxide from the atmosphere.