Recruitment of volunteers, an approach to crop establishement for Lesquerella in low resource environments

BAR-LAMAS, M, GOZALES-PALEO, L, RAVETTA, D.A.

Chillan, Chile

Congreso; AAIC 21st Annual Meeting. International Conference: The next generation of Industrial Crops, Processes and Products. Termas de Chillán, Chillán, Chile. 14-19 November 2009.; 2009

Association for the Advancement of Industrial Crops, USA

Traditional crop management practices (such as sowing) are not always suitable in arid lands, because they may lead to losses of organic matter of the top soil and increase the risk of erosion and desertification. An alternative way to seeding is to reestablish the crop using volunteer recruitment. We present a study in four Lesquerella (Brassicaceae) species with an incipient degree of domestication including high levels fruit dehiscence. This dehiscence generates an important loss of seeds, which enhance the seed-bank and in turn germinate and generate new seedlings which can be used to re-establish the crop. Seed dispersal represents a link between seed production and seedling establishment and determines the spatial arrangement. Emergence and survival of seedlings are mainly controlled by water availability in the top soil layer and the micro-environment close to the soil surface. The goal of this study was to characterize volunteer recruitment in Lesquerella as a new tool to reestablish the crop. We studied annuals (L. gracilis and L. angustifolia) and perennials (L. pinetorum and L. mendocina), and determined seed dispersal, emergence and survival of seedlings and the effect of water and density as modulators of final density of the new stand.  A split-plot field experiment was conducted in Chubut, Argentina (43¨¬ 21¢¥ 31¢¥¢¥ S; 65¨¬ 38¢¥ 39¢¥¢¥ W), with three factors: specie, water availability and density (¥äi). Seed dispersal was evaluated at physiological maturity, using seed-traps. We marked six plots per treatment after the first germination pulse. On each plot the number of seedlings was recorded once a week. At physiological maturity all plants were harvested to determine total biomass, allocation, and seed -yield and components. Seed dispersal was higher in L pinetorum and L. mendocina (4.7 Kg/Ha) than in L. gracilis and L. angustifolia (3.4Kg/Ha). No significant differences were found between water availability treatments (p = 0.92). Only L. pinetorum¢¥s seeds germinated in autumn, which coincided with the sowing date proposed for the establishment of this crop in Chubut. There was no interaction ¥äi * water availability (p = 0.62) for the emergence and survival of seedlings.  Emergence and survival was different among ¥äi (p<0.0001): the density of seedlings was stable in time for the low and medium ¥äi, and decrease only at the highest ¥äi. Low water availability resulted in a reduction in seedling density (p<0.05). The seeds of L. angustifolia and L. gracilis germinated in spring, and the plants completed their life-cycle in just three months. The seed of L. mendocina remained dormant in the seed-bank.             The amount of seed dispersal was adequate for the reestablishment of the crop in the perennial species, with similar seeding-rate than reported for L. fendleri (4.5 Kg/Ha). Our results show that the survival of seedling is modulated by a density dependent mechanism, and seems to be independent of the water availability. Of the four species evaluated, only L. pinetorum showed adequate germination timing and growth cycle for the target environment although a larger field experiment is needed to corroborate our results. Volunteer recruitment could be considered as a way to reestablish the crop in other oil-seed crops in arid and semi arid lands.