Growers planting cross pollinated crops, such as corn, who desire to preserve the identity of these crops or to minimize the potential for these crops to outcross with adjacent fields of the same crop kind are instructed to use the same generally accepted practices to manage mixing that are used in any of the currently grown identity preserved crops of similar crop kind.
- In identity preserved production systems, growers are only concerned with cross-pollination of plants that are in different fields. Growers should take into account the following factors that can affect the occurrence and extent of cross-pollination to or from other fields.
- The amount of pollen produced within the field. The pollen produced by the crop within a given field, known as pollen load, is typically high enough to pollinate all of the plants in the field. Therefore, most of the pollen which may enter from other fields falls on plants that have already been pollinated with pollen that originates from plants within the field.
- The existence and/or degree of overlap in the pollination period of crops in adjacent fields. This will vary depending on the maturity of crops, planting dates and the weather. For corn, the typical pollen shed period lasts from 5 to 10 days a particular field. Therefore, viable pollen from neighboring fields must be present when silks are receptive in the recipient field in this brief period to produce any grain with traits introduced by the out of field pollen.
- Distance between fields of different varieties or hybrid of the same crop. The greater the distance between fields the less likely their pollen will remain viable and have an opportunity to mix and produce an outcross. For instance in corn, published studies reported that most cross pollination occurs less than 30 feet downwind from the pollen source. Most cross-pollination occurs within the outermost few rows of the field. In fact many white and waxy corn production contracts ask the grower to remove the outer 12 rows (30 ft.) of the field in order to remove most impurities that could result from cross-pollination with nearby yellow dent corn.
- Distance pollen moves. How far pollen can travel depends on many environmental factors including weather during pollination, especially wind direction and velocity, temperature and humidity. All these factors will vary from season to season, from day to day and from location to location.
- The orientation and width of the adjacent field in relation to the dominant wind direction. Fields oriented upwind during pollination will show dramatically lower cross pollination for wind pollinated crops like corn compared to fields located downwind.
Identity Preserved Production
Some growers may choose to preserve the identity of their crops to meet specific markets. Examples of Identity Preservation (I.P.) corn crops include production of seed corn, white, waxy or sweet corn, specialty oil or protein crops, food grade crops and any other crop that meets specialty needs, including organic and non-genetically enhanced specifications. Growers of these crops assume the responsibility and receive the benefit for ensuring that their crop meets mutually agreed contract specifications.
Based on historical experience with a broad range of I.P. crops, the industry has developed a set of generally accepted I.P. agricultural practices. These practices are intended to manage I.P. production or quality specifications and are applicable to broad range of I.P. needs. The accepted practice with I.P. crops is that each I.P. grower has responsibility to implement any necessary processes. These processes may include sourcing seed appropriate for I.P. specifications, field management practices such as might cross-pollinate, and harvest and handling practices designed to prevent mixing and maintain product quality. These extra steps associated with I.P. crop production are generally accompanied by incremental increases in cost of production and consequently of the goods sold.