Effect of Herbage Density, Height and Age on Nutrient and Invertebrate Generalist Predator Abundance in Permanent and Temporary Pastures

Rémi Toupet,Alastair T Gibbons,Sara L Goodacre,Matt J Bell

doi:10.3390/land9050164

Abstract

The aim of this research was to assess differences in the quantity and quality of herbage and invertebrate generalist predator abundance among permanent and temporary pastures. Two permanent pastures and four temporary ley pastures (either one year or two years since being sown) were monitored weekly for 10 weeks in the spring. Permanent pastures included a diverse range of native UK grass species, and temporary ley pastures were predominantly perennial ryegrass (Lolium perenne) with or without white clover (Trifolium repens). Weekly measurements of herbage height (in centimeters), herbage cover (fresh and dry matter in kg per hectare) and herbage density (fresh and dry matter in kg per hectare per centimeter) were obtained for each field, along with lycosid spider and carabid beetle abundance. Weekly pasture samples were used to obtain nutrient concentrations of dry matter, crude protein, neutral detergent fibre (NDF), acid detergent fibre (ADF), ash, oil, sugars, digestible organic matter in the dry matter (DOMD) and metabolisable energy (ME) in the herbage as a measure of forage quality for grazing or harvesting. A linear mixed model was used to assess the effect of sward age, herbage density and height on herbage production, nutrient concentrations and invertebrate abundance. Although this study showed that permanent pastures were associated with lower nutrient concentrations of crude protein, ash, oil and ME compared to younger and predominantly perennial ryegrass pastures, the older pastures were associated with higher carabid numbers. Furthermore, permanent pastures had a higher density of dry matter herbage compared to younger pastures, and more dense and taller swards were associated with higher lycosid numbers. The study suggests that within pastures of 3 to 20 cm height, increasing the height and density of swards increases both ME and oil concentrations in herbage, therefore enhancing forage nutrient quality. Older and more permanent pastures can be beneficial for plant and invertebrate generalist predator populations, and still provide a useful source of nutrients for forage production.

Highlights

Humankind relies on domesticated herbivorous mammals, such as ruminants, to produce edible food, fiber and labour
The current study explores the association between herbage production metrics, sward age and the presence of grassland generalist predator invertebrates
The coefficient of variation in herbage height is high at 50%, which results in coefficients of variation in fresh herbage density of 24% and dry matter herbage density of 25%

Summary

Introduction

Humankind relies on domesticated herbivorous mammals, such as ruminants, to produce edible food (e.g., meat and milk), fiber and labour. Some 37% of the world’s terrestrial land area is grassland, which provides a source of nutrients for animals if managed sustainably [1]. Land 2020, 9, 164 are both important for food production and environmental management [2]. In the UK, grassland area can be subdivided into two main groups: uncultivated grassland, including rough and hill grazing (representing 5.1 million ha), and more managed grassland, including permanent and temporary leys (5.1 and 1.4 million ha respectively) [4,6]. Temporary leys are replaced within five years of sowing and are often part of an arable rotation to help restore soil fertility and reduce weed, pest and disease problems, whereas permanent pastures are grasslands of more than five years old [5]. Permanent pasture swards generally host a more diverse range of native species, which in the UK include perennial ryegrass (Lolium perenne), bents (Agrostis spp.), meadow grasses (Poa spp.), timothy (Phleum pratense), Yorkshire fog (Holcus lanatus) and cocksfoot (Dactylis glomerata) [7]

Objectives

Methods

Results

Discussion

Conclusion