Crop residues are waste materials generated by

agriculture Agriculture encompasses crop and livestock production, aquaculture, and forestry for food and non-food products. Agriculture was a key factor in the rise of sedentary human civilization, whereby farming of domesticated species created ...

. The two types are: * Field residues are materials left in an agricultural field or

orchard An orchard is an intentional plantation of trees or shrubs that is maintained for food production. Orchards comprise fruit tree, fruit- or nut (fruit), nut-producing trees that are generally grown for commercial production. Orchards are also so ...

after the crop has been harvested. These residues include stalks and stubble (stems),

leaves A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, ...

and seed pods. Good management of field residues can increase efficiency of

irrigation Irrigation (also referred to as watering of plants) is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has bee ...

and control of

erosion Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...

. The residue can be ploughed directly into the ground, or burned first. In contrast, no-till, strip-till or reduced-till agriculture practices are carried out to maximize crop residue cover. * Process residues are materials left after the crop is processed into a usable resource. These residues include husks, seeds, bagasse, molasses and

root In vascular plants, the roots are the plant organ, organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often bel ...

s. They can be used as animal fodder and soil amendment, fertilizers and in

manufacturing Manufacturing is the creation or production of goods with the help of equipment, labor, machines, tools, and chemical or biological processing or formulation. It is the essence of the secondary sector of the economy. The term may refer ...

Measurements

Simple line-transect measurements can be used to estimate residue coverage. The amount of crop residues can also be estimated using photographic techniques, or remote sensi

Economic value

Crop residues can be used effectively in many ways: * Biofertilizer: Most discussions about the

economic value In economics, economic value is a measure of the benefit provided by a goods, good or service (economics), service to an Agent (economics), economic agent, and value for money represents an assessment of whether financial or other resources are ...

of crop residues focus on the equivalent fertilizer cost of the nutrients within. Although crop residues contain both macronutrients and micronutrients, only macronutrients such as

nitrogen Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...

phosphorus Phosphorus is a chemical element; it has Chemical symbol, symbol P and atomic number 15. All elemental forms of phosphorus are highly Reactivity (chemistry), reactive and are therefore never found in nature. They can nevertheless be prepared ar ...

potassium Potassium is a chemical element; it has Symbol (chemistry), symbol K (from Neo-Latin ) and atomic number19. It is a silvery white metal that is soft enough to easily cut with a knife. Potassium metal reacts rapidly with atmospheric oxygen to ...

and

sulfur Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...

are economically significant. * Use in agronomic practice as strawbed to produce crops (e.g. in strawberry cultivation). They are widely used in mushroom cultivation. The residues after mushroom cultivation can act as good substrate for composting and biofertilizer applications. * Particle board: Recent developments suggest potential use of crop residues in the manufacture of particle board.

Biofuel production from crop residues

Because of the high carbohydrate content, crop residues can be considered as an appropriate feedstock to produce biofuels. Some algorithms have been developed to estimate the potential capacity of biofuel production from agricultural residues. Based on the experimental data obtained from a study that used ethanol organosolv pretreated rice straw to produce

biohydrogen Biohydrogen is hydrogen, H2 that is produced biologically. Interest is high in this technology because H2 is a clean fuel and can be readily produced from certain kinds of biomass, including biological waste. Furthermore some photosynthetic micro ...

using ''Enterobacter aerogenes'', the annual global amount of collectable rice straw (not total produced straw) for biofuel production was estimated about 249 million tonnes, that could approximately produce 355.78 kilotonnes of hydrogen and 11.32 million tonnes of lignin by the proposed organosolv technology and it was found that China contributes to about 32% of global potential capacity to produce biohydrogen from rice straw.

Mineralization

Nutrients in most crop residue are not immediately available for crop use. Their release (called mineralization) occurs over a period of years. The biological processes involved in soil nutrient cycles are complex. As a rough guide, cereal

straw Straw is an agricultural byproduct consisting of the dry wikt:stalk, stalks of cereal plants after the grain and chaff have been removed. It makes up about half of the crop yield, yield by weight of cereal crops such as barley, oats, rice, ry ...

releases about 10 to 15 per cent of its nutrients and pea residues release about 35 percent of their nutrients by the next year. The speed of mineralization depends on the nitrogen and

lignin Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidit ...

(fiber) content, soil moisture, temperature, and degree of mixing with the soil. N is released fairly quickly from residue when the content is higher than 1.5 per cent (such as in pea residues). In contrast, below 1.2 per cent (such as cereal residue), soil-available N is fixed (called immobilization) by the microbes as they decompose the residue. Thus pea residue would have short- and long-term benefits to soil fertility, whereas cereal straw would reduce next year's soil supply of available nutrients. Over time, the nutrients fixed by soil microbes and humus are released and available to crops. Nutrients from residue are not fully recovered by crops. Just like fertilizer nutrients, nutrients released from crop residue into the soil are susceptible to losses such as leaching (N and S), denitrification (N), immobilization (N, P, K and S), and fixation (P and K).

Efficiency of nutrient uptake

The efficiency of nutrient uptake by crops from fertilizers or residue release is generally thought to be similar. For example, about 50 percent recovery of N in the above-ground plant in the first year. There is some residual benefit of fertilizers as the crops take up a small amount of the nutrients two and three years later. Fertilizer placement can significantly affect the efficiency of crop uptake. The impact of residue placement (buried by

tillage Tillage is the agriculture, agricultural preparation of soil by mechanical wikt:agitation#Noun, agitation of various types, such as digging, stirring, and overturning. Examples of manual labour, human-powered tilling methods using hand tools inc ...

or left on the surface in zero tillage) on nutrient cycling and efficiency is under study. Thus, the practice of calculating the fertilizer equivalent value of the nutrients in crop residue is a reasonable guide to estimating the partial value of crop residues.

References

* Alemayehu Mengistu. 1985. ''Feed resources in Ethiopia''. A paper presented at the Workshop on Animal Feed Resources for Small Scale livestock Producers, 11–15 November 1985, Nairobi, Kenya. 12 pp. * {{cite journal , last1 = Butterworth , first1 = M.H. , last2 = Mosi , first2 = A.K. , year = 1986 , title = The voluntary intake and digestibility of combinations of cereal crop residues and legume hay for sheep , journal = ILCA Bulletin , volume = 24 , pages = 14–17

External links

Field residue management benefits
Crops Biofuels