Using companion plants to assist Pinus patula establishment on former agricultural lands

Companion or nursing taxa may aid the establishment of agricultural and forestry crops by improving soil N status (if legume) and soil structure, and by reducing soil erosion and suppressing weedy species. This study's objectives were to test the applicability of soybean and weeping love grass as companion plants for assisting Pinus patula establishment on former agricultural lands (oldlands), and their capacity for suppressing growth of weedy species. Two experimental trials were conducted which involved growing pine, soybean, weeping love grass and an assortment of weedy species in monocultures and mixtures in pots containing oldland and plantation soils. Pine height and stem diameter were measured at monthly intervals, with total biomass accumulation in all taxa determined 14 months after planting. In the presence of soybean, both shoot and root growth of pine seedlings were enhanced, but root growth was reduced in the presence of weeping love grass. In the presence of the weedy species assortment, pine stem diameter, height, shoot and root biomass were all decreased. In contrast, total biomass accumulation of both soybean and weeping love grass was unaffected by the presence of the weed species assortment. However, the total biomass of this assortment was reduced in the presence of these two species. It is concluded, that P. patula establishment on oldlands infested with agronomic weeds may be improved by cultivating this species together with soybean.