No abstract

The ability of legumes to fix N and improve forage productivity and nutritive value makes them a vital component of temperate pastures, but reduced productivity and persistence can occur under grazing compared with mechanical harvest. Our objective was to determine plant maturity and stocking density effects on productivity, nutritive value, and legume persistence of legume–grass mixtures. Temperate grass paddocks were overseeded with alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.), white clover (Trifolium repens L.), birdsfoot trefoil (Lotus corniculatus L.), or nothing in 2013 and rotationally grazed with Holstein (Bos taurus) heifers (450 kg mean body weight [BW]) in 2014 and 2015 at a low (78,400 kg BW ha−1) or high (336,000 kg BW ha−1) stocking density, or mechanically harvested, when red clover was at a mature or vegetative stage of development. Forage yield and nutritive value were measured at each defoliation event. Legume persistence was measured each spring. Grass monoculture and overseeded canopies generally had greater productivity when grazed at vegetative stage compared with mechanical harvest or grazing at mature stage. Alfalfa was the only legume to consistently respond to stage of development, having 14% greater cover when defoliated at mature stage. Legumes generally had the lowest cover when grazed at high stocking density; white clover was persistent under all defoliation regimes. Although grazing at a high stocking density and mature developmental stage may provide soil benefits, our results suggest that grazing at vegetative stage and a low stocking density optimizes productivity, nutritive value, and persistence of legume–grass mixtures.

The accumulation of soil organic matter (SOM) is vital to the agronomic and environmental functioning of agroecosystems, yet the relative influence of inherent soil properties and agricultural management practices on SOM dynamics are not often addressed in individual studies. Using a network of 218 operating farm fields across Wisconsin and southern Minnesota, USA, this research employs single variable analysis (ANOVA and regression) and regression tree analysis to assess the effects of soil properties (texture, drainage class, pH) and management variables related to crop rotation, tillage, cover cropping, and manure application on SOM, as well as total organic carbon (TOC) and total nitrogen (TN) in the upper 15 cm. Single variable analysis revealed that greater SOM, TOC, and TN were associated with poorly drained soil, tile drained fields, high-clay content soil, and high biomass crop rotations. Soil organic matter (SOM) and TOC were strongly related (R2=0.71), but different regression trees were produced; SOM was most influenced by clay content, while TOC was most influenced by drainage class. Future benchmarking of SOM should be conducted with drainage and texture class categories. The rapid building of data sets thorough unstructured sampling, including an abundance of meta-data, should be a research priority in agricultural science.

The accumulation of soil organic matter (SOM) is vital to the agronomic and environmental functioning of agroecosystems, yet the relative influence of inherent soil properties and agricultural management practices on SOM dynamics are not often addressed in individual studies. Using a network of 218 operating farm fields across Wisconsin and southern Minnesota, USA, this research employs single variable analysis (ANOVA and regression) and regression tree analysis to assess the effects of soil properties (texture, drainage class, and pH) and management variables related to crop rotation, tillage, cover cropping, and manure application on SOM, as well as total organic carbon (TOC) and total nitrogen (TN) in the upper 15 cm. Single variable analysis revealed that greater SOM, TOC, and TN were associated with poorly drained soil, tile‐drained fields, high clay content soil, and high biomass crop rotations. SOM and TOC were strongly related (R2 = 0.71), but different regression trees were produced; SOM was most influenced by clay content, while TOC was most influenced by drainage class. Future assessment for the building of SOM or TOC should be conducted with drainage and texture class categories and on a regional basis, given that these factors influence the practices that occur within landscapes. A rapid building of datasets through unstructured sampling, including an abundance of metadata, should be a research priority in agricultural science to identify practices to build SOM on a regional basis.