User:Desmanthus4food/Perennial grains
While many fruit, nut and forage crops are long-lived perennial plants, all major grain crops are annuals or short-lived perennials grown as annuals. Scientists from several nations have argued that perennial versions of todays grain crops could be developed and that these perennial grains could make grain agriculture more sustainable.
Rationale
Cultivation often has a negative impact on provision of [ecosystem] services. For example, cultivated systems tend to use more water, increase water pollution and soil erosion, store less carbon, emit more greenhouse gases, and support significantly less habitat and biodiversity than the ecosystems they replace
The Millenium Ecosystem Assessment [1]
The 2005 Synthesis Report of the United Nations’ Millenium Ecosystem Assessment program labeled agriculture the “largest threat to biodiversity and ecosystem function of any single human activity.” [1] Perennial grains could reduce this threat, according to the following logic:
- Most agricultural land is devoted to the production of grain crops: cereal, oilseed, and legume crops occupy 75% of US and 69% of global croplands. These grains include such crops as wheat, rice, and maize; together they provide over 70% of human food calories [2]
- All these grain crops are currently annual plants which are generally planted into cultivated soil.
- Frequent cultivation puts soil at risk of loss and degradation.[1]
- This "central dilemma" [3] of agriculture in which current food production undermines the potential for future food production could be escaped by developing perennial grain crops that do not require tilling the soil each year. No-till technology enables short-lived (annual) crops to be grown with less intense tillage, but perennial plants provide the most protection for the soil.[4]
A dense stocking of perennial plants-whether trees, shrubs, or herbs-in an agroecosystem increases the likelihood that the soil will be covered continuously, moderating oscillations in temperature and humidity that can damage the soil
J.J. Ewel (1986) [4]
Methods for developing perennial grains
Potential disadvantages of perennial crops
- Perennial grain crops are in the early stages of development and may take many years before achieving yields equivalent to annual grains.
- Crop rotations with perennial systems are possible, but the full rotation will necessarily take longer. For example, a perennial hay crop [5] like alfalfa is commonly rotated with annual crops or other perennial hay crops after 3-5 years. The slower pace of rotation--compared with annual crops-- could allow a greater buildup of pathogens, pests or weeds in the perennial phase of the rotation.
- In the absence of tillage, and in soils with depleted organic matter, crops with large root systems may build up organic matter to the point that nearly all of the soil nitrogen and phophorus is immobilized. When this happens, productivity may decline until either the organic matter builds up to a level where equilibrium is reached between nutrient mineralization and nutrient immobilization or fertilizer is added to the system.
- Perennial plants may intercept and utilize more of the incoming rainfall [6] than annual plants each year. This may result in water tables dropping a meter or more or reduced surface flow to rivers.
- Wide replacement of annual with perennial plants on agricultural landscapes could stabilize soils and reduce nitrate leaching to the point that the delivery of sediment and dissolved nitrogen to downstream landscapes could be reduced. Farmers in these areas may currently rely on these nutrient inputs. On the other hand, other sectors might benefit from improved water quality.
Advantages of perennial crops
Several claims have been published [3]:
- Greater access to resources through a longer season.Perennial plants typically emerge earlier than annuals in the spring and go dormant in the autumn well after annual plants have died. The longer growing season allows greater interception of sunlight and rainfall. For example, In Minnesota, annual soybean seedlings emerge from the soil in early June. By this time perennial alfalfa has grown so much that it is ready for the first harvest. Therefore, by the time a soybean crop has just begun to photosynthesize, a field of alfalfa has already produced about 40% of the season’s production [7].
- Greater access to resources through a deeper rooting zone. Most long--lived plants construct larger, deeper root systems than short-lived plants adapted to the same region . Deeper roots enable perennials to "mine" a larger volume of soil each year[8]. A larger volume of soil also available for exploitation per unit of cropland also means a larger volume of soil water serves as a reservoir for periods without rainfall.
- More efficient use of soil nutrients. Leaching of nitrogen from fertilizer has been found to be much lower under perennial crops such as alfalfa (lucerne) than annual crops such as maize [9]. A similar phenomenon is seen in unfertilized fields harvested for wild hay [10]. While adjacent wheat fields required annual inputs of fertilizer, the wild perennial grasses continued to produce nitrogen-rich hay for 75 to 100 years with no appreciable decline in productivity or soil fertility. Presumably, the larger root systems of the perennial plants and the microbial community they support intercept and cycle nutrients passing through the system much more efficiently than do the ephemeral root systems of crop plants.
- Sustainable production on marginal lands. Cassman et al. (2003) wrote that for large areas in poor regions of the world, “annual cereal cropping …is not likely to be sustainable over the longer term because of severe erosion risk. Perennial crops and agroforestry systems are better suited to these environments.” [11] Current perennial crops and agroforestry systems do not produce grain. Grain provides greater food security than forage or fruit because it can be eaten directly by humans (unlike forage) andit can be stored (unlike fruit) for consumption during the winter or dry season.
Potential Tradeoffs associated with domestication or perennialization
See also
- Perennial_rice
- Perennial_sunflower
- Plant breeding
- Grains (agronomic)
- Slash-and-burn agriculture
- Subsistence agriculture
References
- ^ a b c Cassman KG, Wood S. 2005. Cultivated systems. Pages 741-876 in Millenium Ecosystem Assessment, ed. Ecosystems and Human Well-Being. Washington (DC): Island Press.Chiras DD, Reganold JP, Owen OS. 2004 Natural Resource Conservation. Upper Saddle River, New Jersey: Prentice-Hall.
- ^ Glover, JD, Reganold, JP. 2010. Perennial grains: Food security for the future. Issues in Science and Technology. Winter 2010:41-47.
- ^ a b TS Cox, JD Glover,DL Van Tassel, CM Cox and LR DeHaan. 2006. Prospects for developing perennial grain crops. BioScience. 56:649-659"
- ^ a b Ewel, J.J. (1986) DESIGNING AGRICULTURAL ECOSYSTEMS FOR THE HUMIDTROPICS. Ann. Rev. Ecol. Syst. 17:245-71
- ^ Markle, G. M.; Baron, J. J.; Schneider, B.A. 1998. Food and Feed Crops of the United States, Second Edition; Meister Publishing Co.: Willoughby, OH.
- ^ Cite error: The named reference
glover®anold_etal2010
was invoked but never defined (see the help page). - ^ CC Sheaffer, Martin NP, Lamb JAFS, Cuomo GR, Jewett JG, Quering SR. 2000. Leaf and stem properties of alfalfa entries. Agronomy Journal 92:733-739.
- ^ JD Glover, et al.2010. Increased Food and Ecosystem Security via Perennial Grains. Science 328:1638-1639.
- ^ Huggins, D.R., Randall, G.W., Russelle, M.P., 2001. Subsurface drain losses of water and nitrate following conversion of perennials to row crops. Agron. J. 93, 477–486.
- ^ [http://www.landinstitute.org/pages/Glover%202009%20AGEE%20InPress.pdf Harvested perennial grasslands provide ecological benchmarks for agricultural sustainability (2010) Jerry D. Glover, Steve W. Culman, S. Tianna DuPont, Whitney Broussard, Lauren Young, Margaret E. Mangan, John G. Mai, Timothy E. Crews, Lee R. DeHaan, Daniel H. Buckley, Howard Ferris, R. Eugene Turner, Heather L. Reynolds and Donald L. Wyse. Agriculture, Ecosystems & Environment. 137:3-12.]
- ^ KG Cassman, A Dobermann, DT Walters, H Yang. 2003. Meeting cereal demand while protecting natural resources and improving environmental quality. Annual Review of Environment and Resources 28:315-358.
Cite error: A list-defined reference named "Wagoner1990" is not used in the content (see the help page).
External links
- Perennial upland rice takes root An article by Paul Cox in the New Agriculturalist.
- The Land Institute A scientific institute in Kansas, U.S.A. with several perennial grain breeding programs.
- the International Rice Research Institute (IRRI)