Proofreading occurs during the ____________ phase of transcr…
Proofreading occurs during the ____________ phase of transcription.
Proofreading occurs during the ____________ phase of transcr…
Questions
Prооfreаding оccurs during the ____________ phаse of trаnscription.
Prооfreаding оccurs during the ____________ phаse of trаnscription.
NO ANSWER REQUIRED TO THIS QUESTION, THIS IS THE CASE STUDY DESCRIPTION. Twо аgrоecоsystems dominаted by аgronomic row crops are located side-by-side in the Southeastern US. This area is dominated by weathered, coarse-textured ultisols, hot and wet summers, and drier and cooler winters. In this area, agronomic row crops (cotton, corn, peanut, soybean) are grown during the summer, whereas winter options include fallows, cover crops, and a few winter cash crop options. Corn and peanut are well-adapted to growing in these conditions, whereas this is the southern limit for soybean. The first grower uses a 2-year rotation of corn and soybean, grown using a “regenerative” approach to management. Consistent with this regenerative approach, local composted poultry manure is used as the base amendment for corn, providing roughly half of the nitrogen requirement for corn at planting – coming from manure however, this nitrogen is not entirely available at planting. The rest of the nitrogen demand for corn is provided by fertigation through an overhead pivot, which is the common irrigation method in the area. This grower doesn’t factor in a “N credit” from their pre-corn cover crop (see below), whereas soybean and cover crops receive no nitrogen fertilization. Irrigation is controlled by a soil moisture sensor, which they acquired through a cost-share program to reduce costs for growers. Since they started applying manure about a decade ago, they have noticed a lower irrigation demand from both cash crops, and they never had to irrigate their cover crop to get it established. Besides nitrogen, other nutrients are added as needed to corn and soybean based on soil testing, using synthetic fertilizers either at planting or through the pivot. The soil testing lab they use is known to recommend higher inputs than extension recommendations, although phosphorus is never required due to the high concentrations they have built since they started using manure. Another component of regenerative management is to reduce soil disturbance. As a result, they use strip tillage for all their crops, and they switched from peanut to soybean several years ago to avoid soil disturbance at harvest. They also use winter cover crops: oat only before soybean, and oat and clover before corn. Cover crops are terminated by herbicide before mowing. Herbicides are also their main form of weed control, given that they can’t till to control weeds. This grower is using genetically modified corn and soy varieties that are both resistant to herbicides and have Bt genes that allow to cut back significantly on insecticide sprays. When the economic threshold for intervention is met however, which invariably occurs, they do not hesitate to use synthetic pesticides to control pests. As previously mentioned, strip tillage is used after all cash cropping and cover cropping phases. Cover crops are terminated with herbicide in the spring, and mowing is used for all cash crop residues and cover crop biomass before strip tillage. Because corn and soybean are not planted and harvested at the same time, there is little competition between these crops for equipment. As a result, each farm operation can be optimized to occur at the ideal time, including rapid planting of cover crops after cash crops are harvested, and rapid cash crop planting after cover crops are terminated. The second grower also uses a 2-year rotation, but a more complex one. Here, corn is grown the first summer, followed by carrots during the winter, peanut the second summer, and an oat winter cover crop, before returning to corn to start a new cycle after two years. Nitrogen fertilization for corn and carrots is done entirely with granular synthetic fertilizers (no fertigation), with one third at planting, and the other two thirds applied as two splits during the season. Peanut and the oat cover crop do not receive N fertilizers. Consistent with other growers in the area, they use a pivot overhead irrigation system that operates on a timer, although they adjust irrigation based on plant growth during the growing season. Similar to grower #1, they use soil testing to apply other nutrients (including gypsum to provide calcium to the peanut), although they use the official extension lab that is more conservative in its nutrient recommendations than private labs. Similar to grower #1, this grower also uses strip tillage after oat termination (i.e., before corn) to reduce soil disturbance. However, as carrot is managed with very little residue from the previous corn, heavy tillage is used prior to planting, with multiple disking operations that cover the entire area of the farm. In addition, as both carrots and peanut need to be dug from the ground, the soil is further disturbed at harvest, followed again by disking the entire area of the farm. This grower does not want to use genetically engineered crops, hence all varieties (corn, carrot, and peanut) do not have pest- or herbicide-resistance traits. As a result, they require more pesticide applications, especially the high-value carrot crop on which they use heavy and preventative fungicide sprays (typically 18 in a season) to prevent issues with Alternaria. Weeds are mostly controlled by regular tillage in this system, as herbicide-resistant varieties are not used, although herbicides are still used at key steps of each growing season. Similar to grower #1, the oat cover crop is planted rapidly after peanut is terminated, and corn is planted rapidly after oat is terminated - note that oat is only mowed in this system, not terminated by herbicide first. However, given that carrots are planted in soil with very little residues, there is an extended decomposition period taking place after corn is harvested to allow for residue decomposition. In addition, because winter growing conditions can vary among years, peanut planting can sometimes be delayed by a few weeks to allow for carrot harvest, which requires the use of a shorter-season variety that yields less. Finally, when a dry spell hits the area in the fall during early cover crop growth, this grower has had to irrigate their cover crop to make sure it's established well.