Changes in pasture root growth and transpiration efficiency following the incorporation of organic manures into a clay subsoil

Abstract

Background & aim This study tested the hypothesis that manure incorporation in the top of the B horizon of a texture-contrast duplex soil would increase root growth and water uptake by pasture grasses. Methods It involved soil columns consisting of a sandy loam topsoil over a dense clay. Four soil treatments included (i) a control profile, and modifications to the upper 10 cm of the clay subsoil involving (ii) a lower bulk density and (iii) the incorporation of poultry and (iv) dairy manure into this layer. Italian ryegrass and prairie grass were grown in separate columns, over 3 growth cycles. Results Manure incorporation decreased root biomass by up to 40% in both grasses, without any reduction in shoot growth. Root distribution varied with roots proliferating in the manured-layers compared with the same layer without the manures, resulting in a doubling of the root length density in the manured layer. Shoot yields in the 2nd growth cycle were similar between treatments, yet there was lower transpiration from the shoots in the manure treatments. This meant that manure incorporation increased transpiration efficiency, as it changed the distribution and architecture of the roots. Conclusion Manure incorporation into subsoil increased transpiration efficiency, and root surface area, rather than shoot biomass, was the controlling factor for transpiration from the shoots of the grasses.

Organic Amendments Influence Soil Water Depletion, Root Distribution, and Water Productivity of Summer Maize in the Guanzhong Plain of Northwest China

“…Consistent with these findings, organic amendments generally exerted a clear improvement on the RLD and RWD of maize relative to CO in our experiment ( Figures 5-7), because both soil temperature and water, being substantially influenced by organic amendments, affected plant root growth [17]. By contrast, Espinosa et al [35] found that manure incorporation severely impaired the total root biomass of grasses when organic amendments were applied in clay subsoil to overcome nutrient deficiencies.…”

Evaluating Dairy Manure as Initial Fertility Driver for Mudflat Soil Amendment

“…The DMA also enhanced shoot and root biomass of pasture grass [33]. Others found that DMA increased the yields of rice [20], wheat and maize [23], Italian ryegrass and prairie grass [33]. The present study showed that DMA increased the biomass of ryegrass grown in the mudflat soil by increasing soil fertility while decreasing soil salinity.…”

“…Miron et al [32] also confirmed that the DMA increased yield of forage. The DMA also enhanced shoot and root biomass of pasture grass [33]. Others found that DMA increased the yields of rice [20], wheat and maize [23], Italian ryegrass and prairie grass [33].…”

Coastal Mudflat Saline Soil Amendment by Dairy Manure and Green Manuring

“…In addition, mudflat saline soil was enriched with alkaline N, available P, and other nutrients from DMA, which provided sufficient nutrients for ryegrass growth as the first green manure. Previous studies also found that DMA increased biomass of sorghum-sudangrass [23], pasture grass, and ryegrass [24] grown in croplands. Biomass of ryegrass, Sesbania, and ryegrass as green manures for three consecutive seasons, tilled into the mudflat saline soil, can be decomposed and converted into soil organic carbon, which subsequently improved the chemical properties of mudflat saline soil.…”