Planting pinto beans
Pinto beans like full sun. They grow best in well-drained soil with a pH of 6.5 to 7. Crumbly soil is preferred to compact soil so that seedlings can emerge easily. Heavy soils are covered with peat, sand, vermiculite or finished compost to prevent them from developing crusts.
Pinto beans are planted in the spring after the danger of frost has passed. Three to four plants per foot are seeded 2 to 2½ inches deep in rows from 20 to 30 inches apart. They can be planted as deep as four inches in dry-land conditions.
If the soil temperature is below 60 degrees Fahrenheit, the seedlings may germinate poorly and the roots of seedlings may rot. Some bean seeds sold commercially have been treated with a fungicide to protect seedlings from disease.
Pinto beans do not require a lot of water, which is why they are popular in the Southwest United States and Northern Mexico. Pinto beans are often irrigated after seeding to aid in germination, but little water is used to keep the soil from becoming too cool.
To assure vigorous leaf growth and healthy blossoms, the plants are irrigated two to four weeks after the seedlings emerge. They are irrigated again a week to 10 days after that to make sure beans are plump and the pods are full. If they are sprinkled, the sprinklers should be turned off between 2 to 3 p.m. so the foliage can dry before sunset. Wet plants at night can be infected with bacterial blight.
Mulch and windbreaks
Mulch helps suppress weeds and keeps the soil warm in early plantings. It also helps the soil retain moisture. After the soil has warmed, pinto beans are mulched with two to three inches of untreated lawn clippings, shredded bark or weathered straw. Black plastic with slits cut for planting the seeds serves the same function. Broadleaf weeds lower yields of pinto beans by 40 to 50 percent, according to field research at Colorado State University.
Strips of windbreak are sometimes used to protect seedlings from damage by wind and blowing sand. Alternately, rye, sorghum and corn are often planted as windbreaks.
Fertilizing and harvesting
If the soil has not been tested, the recommendation of Purdue University is that before planting, one cup of 5-10-10 fertilizer be applied to every 50 feet of plants. The fertilizer should be worked six inches into the soil.
Excess nitrogen in light soils can cause heavy growth of stems and leaves, and a poor yield of beans. After heavy rains, a side-dressing of one cup of ammonium nitrate may be applied alongside each 50 feet of pinto bean rows and lightly watered in.
When 70 percent of the pods are yellow, they are ready for harvest.
Disease and crop rotations
Pinto beans are susceptible to fungal disease, including root and stem rot, plus blight and bean mosaic, both bacterial diseases. To encourage vigor, pinto beans should be rotated every three to four years with corn, cotton, sorghum, wheat or vegetables, according to horticulturists at Texas A&M University.
Pinto beans should not be planted in rotation after beans, peas, potato or sugar beat crops that were infected by root and crown rots. Short rotations and continuous cropping can cause fungi to build up in the soil. Long crop rotations are preferred.