In the Southeast, forages are the primary feed source for livestock production systems due to the diversity of adapted forage species, favorable climate conditions and lower production costs. With the growing population, agricultural systems face challenges in increasing food and fiber production while minimizing negative environmental impacts. Forage systems play an essential role in delivering ecosystem services, and the management practices used directly impact the sustainability of those systems (Fig. 1). Ecosystem services (ES) are defined as the “benefits people obtain from ecosystems”, and they are classified into four categories: cultural, provisioning, regulating, and supporting benefits. Some examples of ES provided by grasslands include carbon sequestration, nutrient cycling, and wildlife and pollinators’ habitat. Management practices affect forage stand production, longevity and resilience, nutrient cycling, animal performance, soil fertility, and health, among others. Therefore, proper management can be an ally in keeping a healthy forage stand over time. Below, a few key points related to ES from forage systems will be briefly discussed.
Energy storage is essential crucial for plant recovery and growth after each harvest event. Harvest frequency (i.e., how often) and intensity (i.e., how closely forage is removed), either by grazing or cutting, directly affect the productivity and persistence of forage systems. For instance, bermudagrass in South Carolina should maintain a stubble height of 3–4 inches and be harvested every 4–6 weeks for optimal regrowth. Adhering to the use of research-based recommended stubble height and adequate (re) growth period of forage species allow for residual leaf area to be left for plants to recover without reducing stored energy reserves over time. Higher than recommended frequency and intensity of harvest events may compromise the ability of forage species to recover and lead to forage stand decline and loss over time. Under grazing management, rotational grazing can help with the uniform removal of forage mass, limiting animals’ access to individual plants for a given time (resting period). This is particularly important when grazing legumes or legume-grass mixtures since animals tend to visit forage legumes more often, which might compromise their persistence over time. Rotational grazing strategies in South Carolina typically involve resting paddocks for 21–28 days, depending on growth conditions. Furthermore, rotational grazing supports uniform forage removal and enhances nutrient distribution from livestock excreta.
Nutrient cycling and redistribution in forage systems. In hay production systems, we export nutrients to other areas where animals feed on the hay harvested. For this reason, there is a limited return and recycling of nutrients from the forages into the system under hay production and a greater reliance on off-farm inputs (i.e., fertilizer) to supply plant nutrient needs. In grazing systems, livestock can return up to 80% of the nutrients consumed back into pastures. Therefore, optimizing the nutrient distribution from animal excretion is vital to improve forage accumulation and quality and soil fertility, especially in low-input systems. Better nutrient distribution can be achieved by employing proper rotational grazing strategies since animals remain in the area for a defined period, avoiding establishing exclusion areas or excessive excreta deposition in particular areas. Also, when feeding hay on pastures, the recommendation is to alternate feeding areas throughout the field to help with better excreta distribution. Nutrient return from litter and root contributions, either by decomposition or exudation of compounds, are common to grazing and hay systems but may occur at different levels. After harvest events, either by grazing or cutting, it is common for parts of the root system to die. This plant material is recycled and incorporated as organic matter, releasing nutrients into the soil over time. Also, dung beetles play a crucial role in nutrient cycling processes and contribute to improved soil conditions in grazing systems.
Carbon sequestration and soil health. Due to limited soil disturbance, soils under perennial grasslands are significant carbon sinks over time. Over time, nutrients are incorporated into the soil through the deposition and decomposition of above- and below-ground plant material, improving soil fertility and enhancing its chemical and physical properties. Some of the residual materials can be incorporated back into the soil as organic matter, enhancing soil structure and fertility. For example, during grazing, it is common for animals to pull out some plants from the soil and even a portion of their roots. If not consumed, that material is decomposed and can contribute to nutrients and organic matter being incorporated into the soil. Soil health refers to the soil’s ability to perform functions that support life on earth. Without soil, producing the food, fiber, and energy needed to sustain human life would not be possible. Soil also helps to protect the earth’s natural resources by filtering water and decomposing harmful chemicals. There has been an increased focus on rebuilding soil health in agricultural lands to conserve soils for future generations. In row crop production systems, practices like reduced tillage and cover cropping are used to improve soil health. There are also management practices that can promote soil health in pastures, such as utilizing rotational grazing and avoiding overgrazing. Some parameters that determine proper soil health include but are not limited to, organic matter content, adequate fertility and pH, and fauna biodiversity.
Written by
Liliane Silva, Extension Specialist
Carlos Garcia, Postdoctoral Fellow
