Shade and nitrogen effects on regrowth dynamics, partitioning, and herbage production of Jiggs Bermudagrass and Mulato-2 brachiaria hybrid.

The objectives of this study were to quantify the effects of shade and N fertilization on C and N availability for plant growth, composition of stubble following defoliation, and partitioning of assimilates.Resumo 307-38

Above and Belowground Biomass Characteristics of Rhizoma Peanut Entries and Their Relationship with Soil C and N.

In forage systems, soil C and N are affected by many factors including above- and belowground biomass, root exudation, defoliation management, and tissue turnover dynamics. There is need to understand the main drivers of soil C and N accumulation under perennial forages, especially those factors associated with differences in growth and canopy characteristics. The objective was to determine soil C and N status and their relationship with above- and belowground characteristics of six rhizoma peanut (RP, Arachis glabrata) entries. Treatments were Apalachee, Chico, Ecoturf, Ona33, Peace, and Tito RP arranged in four replicates of a randomized complete block design. Stands were planted in 2010 and harvested twice per year after establishment. The area was previously a long-term bahiagrass (BH, Paspalum notatum) sward. Herbage accumulation (HA) and root-rhizome mass (RRM) and accumulation rate (RRA) were measured in 2016 and 2017. Existing litter and soil to 0-5, 5-10, and 10-20-cm depths were sampled in September and December 2018. Herbage and litter samples were harvested using two, 0.25-m2 quadrats per plot. Three 10-cm diameter cores (20-cm depth) were taken per plot to measure RRM, while RRA was measured using ingrowth cores. Soil C and N concentrations were determined by dry combustion. Among entries, HA ranged from 6.7 to 10.5 Mg ha-1, RRM from 5.5 to 8.6 Mg ha-1, RRA from 10 to 33 kg ha-1 d-1, and litter mass from 1800 to 2300 kg ha-1. Litter mass and RRA were negatively correlated to C and N stocks in the 0-5 cm layer and positively correlated with those in the 10-20 cm layer. This may be due to mineralization of nutrients in surface soil and use by plants to accumulate biomass, followed by release of exudates and tissue turnover at depth. Soil C and N stocks were less responsive to sward characteristics than expected