Determining Thresholds for Grassland Renovation by Sod-Seeding

Victor P Rueda-Ayala,Mats Höglind

doi:10.3390/agronomy9120842

Victor P Rueda-Ayala, Mats Höglind

Open Access

https://doi.org/10.3390/agronomy9120842

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Abstract

This study aimed at identifying optimal sward conditions for successful establishment of red clover (Trifolium pratense L.) through sod-seeding two typical Norwegian grassland systems dominated by timothy (Phleum pratense L.) and perennial ryegrass (Lolium perenne L.), respectively. A total of four sod-seeding trials were implemented, two in late summer (SUM) and two in spring (SPR), one for each sward type and time point for reseeding. The sward coverage status was the basis for threshold definition, and image analysis techniques were used for objective coverage estimation of living plants, dead material and bare soil. Plots with different coverage levels (0–100% of the soil covered by vegetation) were created by spraying a broad-spectrum herbicide (glyphosate) in a spot-wise pattern, mimicking common types of patchiness caused by stressful weather events, e.g., frost or mechanical damage from wheels or hoofs. Seed germination and emergence started similarly in all coverage ranges. However, as time progressed clover seedlings started to die at a coverage dependent rate, and at the final harvest red clover dry matter (RCDM) was the lowest on plots with the highest pre-seeding coverage level. Dose-response curves explained these relationships and allowed estimating the effective-coverage ( E C o v 80 ), being the initial sward coverage at which 80% of all established red clover plants contributed significantly to the total biomass. Above 2500 kg ha−1 RCDM were produced on timothy ( E C o v 80 : 15–50%) in SUM, while less than 1000 kg ha−1 RCDM were produced on ryegrass ( E C o v 80 : ± 10 % ), indicating better conditions for clover establishment in timothy compared with ryegrass. In SPR, an E C o v 80 : 10–15% allowed a good red clover estabishment in ryegrass at cut 3, while RCDM was important and significant in timothy even between E C o v 80 20 and 60%, at cut 2 and cut 3, respectively. These thresholds for sod-seeding mark the challenges to introduce red clover in dense swards and could be applicable for grassland renovation with other desirable legume and grasses species. Our findings represent particular soil and climatic characteristics of the study site, thus should be taken with caution. Due to the lack of experimentally and sytematically determined thresholds for reseeding, future studies could benefit from our experimental approach, as a base for more complex, multi-site and multi-seasonal investigations, and farmers could use these thresholds for decision making on successful grassland renovation, to avoid wasting seed resources and yield loses.

Highlights

Forage grasses serve as the main source of energy and nutrients for ruminant livestock in many regions of the world
Due to the lack of experimentally and sytematically determined thresholds for reseeding, future studies could benefit from our experimental approach, as a base for more complex, multi-site and multi-seasonal investigations, and farmers could use these thresholds for decision making on successful grassland renovation, to avoid wasting seed resources and yield loses
Forage yield was evaluated as dry weight of grass and red clover biomass at final harvest

Summary

Introduction

Forage grasses serve as the main source of energy and nutrients for ruminant livestock in many regions of the world. Grass-based dairy and meat production constitutes the economic backbone of agriculture in Northern Europe. Sod-seeding is often used in cases where plowing is difficult or risky, when the botanical composition of the sward needs to be improved, or on farms seeking to exploit the feed value and N-fixing properties of legumes [3]. Direct drilling of desired forage species into the existing sod, i.e., sod-seeding, aims at increasing both grass productivity and quality [4,5]. Due to the low demands of labour, equipment and fuel, and by keeping the original vegetations sod-seeding reduces the risk of soil erosion and improves economic, environmental and agronomic grass management assets, without the production loss during the establishment season, associated with reseeding after plowing [6]

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