The effect of intercropping annual ryegrass with pinto beans in mitigating iron deficiency in calcareous soils.

摘要

Dry beans are grown extensively throughout the western Great Plains. The high-pH soils prevalent in this region limit the availability of many micronutrients, especially iron. In 2002 a Goshen County, Wyoming farmer observed that pinto beans intercropped with annual ryegrass did not exhibit iron-deficiency chlorosis and produced higher yields than beans grown without the ryegrass. Field studies were conducted on the same farm in 2006 to determine if a ryegrass intercrop results in increased iron concentration in pinto beans. Treatments included bean-ryegrass intercrop, beans planted in ryegrass residue incorporated in the soil, and beans planted alone. Soil iron concentration increased for all treatments (p<0.10) over the first 76 days of the experiment. There was also significantly more soil organic matter and significantly lower soil pH (p<0.10) in plots with ryegrass compared to beans alone. Iron concentration declined, though not significantly, in bean leaves over the study period with a steep decline over the first sampling interval in the monoculture plots compared to bean-ryegrass plots.