Land equivalent ratio, grain and pod yield and ethereal extract of Helianthus annuus L. in monoculture and associated with Pisum sativum L. in function of stabilized urea.

The aim of this study was to assess the land equivalent ratio, biomass, grain yield and ethereal extract of Helianthus annuus in monoculture and associated with Pisum sativum in function of stabilized urea (0, 40, 80 kg N/ha) in El Cerrillo, Mexico. It was also estimated pod yield obtained by P. sativum as a pure stand and associated with H. annuus. The six treatments (in each experiment) were evaluated in a 2 × 3 factorial experiment in a randomized complete block design with four replications. When F values were significant, the honestly significant difference test at the 5% level of significance was used. The principal component analysis was also used to study the interrelationship among the six treatments and seven variables. The results observed in the biplot indicated that the largest original variation in the data was adequately represented in the first two principal components since both accumulated 87.9%. This analysis revealed that the treatments of H. annuus in monoculture and H. annuus + P. sativum fertilized with 80 kg N/ha were those which achieved the highest grain yields (287.7 and 285 g/m2, respectively). The superiority of these treatments is attributed to the fact that leaf area index and total biomass showed to be the main yield component of H. annuus. The value of the land equivalent ratio (1.47) obtained with the supply of 80 kg N/ha indicates an advantage in the grain and pod yields of the association of both species by 47% over their respective monocultures. As a result, this planting system is a good choice for farmers with scarce economic resources in the region.