Potential Disadvantages of Perennial Grain

  1. Does not address food security today. Perennial grain crops are in the early stages of development and may take many years before achieving yields equivalent to annual grains.
  2. Makes crop rotation more difficult. Crop rotations with perennial systems are possible, but the full rotation will necessarily take longer. For example, a perennial hay crop. 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.
  3. Builds soil organic matter at the expense of plant productivity. 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.
  4. Hydrological impacts. Perennial plants may intercept and utilize more of the incoming rainfall. than annual plants each year. This may result in water tables dropping and/or reduced surface flow to rivers.
  5. Reduced nutrient delivery to downstream farms. 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.
  6. Improved habitat for pests. If fields are not left bare for a portion of the year, rodents and insects populations may increase. Burning of the stubble of perennial grains could reduce these populations, but burning may not be permitted in some areas. Furthermore, rodents and insects living underground would survive burning, whereas tillage disrupts their habitat.

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Perennial Grain".