We examined the effect of a labile soil amendment, compost, and recalcitrant biochar on soil microbial community structure, diversity, and activity during turfgrass establishment. Two application rates of biochar (B1 at 12.5 t ha^-1and B2 at 25 t ha^-1), a 5 centimeter (cm) green waste compost treatment (CM) in top soil, a treatment with 12.5 t ha^-1biochar and 5 cm compost (B1+CM), and an unamended control (CK) treatment were prepared and seeded with tall fescue. Overall, results of phospholipid fatty acid analysis (PLFA) profiling and Illumina high-throughput sequencing of 16S rRNA genes amplified from soil DNA revealed significant shifts in microbial community structures in the compost amended soils whereas in biochar amended soils communities were more similar to the control, unamended soil. Similarly, increases in enzymatic rates (6–56%) and nitrogen-induced respiration (94%) were all largest in compost amended soils, with biochar amended soils exhibiting similar patterns to the control soils. Both biochar and compost amendments impacted microbial community structures and functions, but compost amendment, whether applied alone or co-applied with biochar, exhibited the strongest shifts in the microbial community metrics examined. Our results suggest application of compost to soils in need of microbiome change (reclamation projects) or biochar when the microbiome is functioning and long-term goals such as carbon sequestration are more desirable.

Competitiveness of erect, semierect, and prostrate cowpea genotypes with sunflower (Helianthus annuus) and purslane (Portulaca oleracea) - Volume 52 Issue 5 - Guangyao Wang, Jeff D. Ehlers, Eddie J. Ogbuchiekwe, Shengping Yang, Milton E. McGiffen

We measured the gas exchange parameters of six onion varieties in two photoperiodic regimes. The photoperiods simulated early (long-day) and late (short-day) onion growing seasons of the high desert regions near Lancaster, California. We used six locally grown onion varieties: RedBull (RB), RedWing (RW), Hybrid Cometa (HC), Granero (YG), Hybrid Valero (HV) and Hybrid SR (HS). For both photoperiod regimes, daylength and temperature were changed weekly to represent the natural progression of field growing conditions. The results show that the onion plants grown under short-daylength (SD) and higher temperature regimes exhibited higher leaf photosynthetic rates and stomatal conductance than onion seedlings grown under the long-day (LD) regime. Onion plants also had different functional leaf traits depending on crop growth environment during the onset of bulbing. The higher photosynthetic rate of the short-day plants coincided with bulb initiation. Onion photosynthesis and stomatal conductance increased at bulb initiation, apparently to provide carbohydrates for growth and storage in the bulb.

The effect of summer cover crop and management system on subsequent fall romaine lettuce ( Lactuca sativa L.) and spring muskmelon ( Cucumis melo L.) growth and yield was evaluated in the Coachella Valley of California from 1999 to 2003. Cover crop treatments included: 1) cowpea [ Vigna unguiculata (L.) Walp.] incorporated into the soil in the fall (CPI), 2) cowpea used as mulch in the fall (CPM), 3) sudangrass [ Sorghum bicolor (L) Moench] incorporated into the soil in the fall (SGI), and 4) a bare ground control (BG). Management system treatments included: 1) conventional system (CON), 2) integrated crop management (ICM), and 3) organic system (ORG). Cowpea cover crop, either incorporated or used as surface mulch, increased lettuce growth and yield by increasing biomass allocation to lettuce leaf and leaf area growth. Cowpea mulch decreased muskmelon leaf and biomass growth and reduced muskmelon yield. Sudangrass produced more biomass than cowpea and reduced lettuce growth and yield. However, in the following spring, the SGI treatment had the highest muskmelon yield. Lettuce growth was significantly affected by management system, while muskmelon growth at the early stage was unaffected. The organic system reduced both lettuce and muskmelon yield compared with CON and ICM management systems.