Corn-faba bean associations in the Peruvian Central Andes

In the communities of the Central Andes of Peru, faba bean and corn seeds are mixed at sowing, resulting in random mixed crops. The proportion of the respective seeds can vary considerably from one year to another. In this system, farmyard manure is the main source of fertilization (1348-10300 kg ha^-1), sometimes extended with limited inorganic fertilization (23-67 kg ha^-1 N). From 2006 to 2008, 19 bean-corn plots were investigated at farm level in different farmer communities of the Mantaro Valley, Central Andes, Peru. NPK and C balances due to the different corn-bean proportions and fertilization levels were evaluated. Moreover, in 2011, an experiment with different area proportions of corn-bean was set up to try to optimize production. Measured biomass varied considerably, depending on sowing proportion, plant density, fertilization level and harvest stage. At harvest, the fresh weight of corn cobs and bean pods ranged from 722 to 8905 kg ha^-1. The fresh weight of the shoot residual biomass incorporated into the soil after harvest varied from 95 to 14752 kg ha^-1. After harvest, the faba bean residue was left on the field. In contrast, corn stalks (1184-21191 kg ha^-1) were removed to be used for fodder. The fresh weight of weed biomass ranged between 889 and 17405 kg ha^-1. It was observed that, by varying the corn-bean proportion over years, farmers can minimize the NPK and C deficits of the production system, with the amount of residual biomass incorporated into the soil. Sowing a 50:50 corn-bean ratio showed a yield advantage, with land equivalent ratios of 1.54 and 1.50 for total (grain+straw) and grain yield, respectively.