Laboratório de Plantas Forrageiras

PROJECTS

Self-thinning principle: interspecific variations, reduced light availability, and suboptimal nitrogen nutrition in brachiarias

In grazed pastures, a compensation mechanism occurs between tiller size and density in response to defoliation height. Shorter pastures have a high density of smaller tillers, while taller pastures have fewer but larger tillers. This process helps maintain a balanced leaf area index (LAI) and supports plant regeneration after grazing. The relationship between tiller size and density follows the "self-thinning law" (this relationship has a slope of -3/2 when analyzed on a logarithmic scale), indicating an inverse relationship between mass and density. However, different species exhibit varying slopes, such as -1, -3/2, and -5/2, each with distinct ecological implications. This suggests that the relationships between LAI, tiller density, and tiller weight vary among species, particularly in temperate pastures, and require further investigation. Thus, this project consists of three studies with the objective of verifying the compensation mechanism in brachiarias, considering species variations, reduced light conditions, and suboptimal nitrogen nutrition. The hypotheses are that for species variations, the lines with a -5/2 slope will overlap; under low light and nitrogen conditions, the slope is expected to vary; and for all three studies, production will align along the same line for different management heights.

Nitrogen fertilization strategies in cool season pastures and their consequences on productivity and diversity in warm season pastures

The South of Brazil has a climate with a wide temperature range and regular rainfall, allowing the cultivation of both cool season and warm season species in the same area, enabling almost year-round animal production on pasture. These environments allow the use of multispecific pastures, where better use of the resources provided by these pastoral ecosystems can be achieved through the complementarity of species from different functional groups. Considering that plant performance is influenced by various biotic and abiotic factors, some of which can be controlled through management, and with nitrogen being the crucial nutrient for forage production, understanding how it is utilized by different species in association during different times of the year is essential for developing sustainable and productive management strategies. Thus, the objective of this study is to identify nitrogen fertilization strategies that maximize forage production while maintaining diversity in a pastoral system composed of annual ryegrass (Lolium multiflorum) seeded onto the perennial species Tifton 85 (Cynodon spp.), kikuyu grass (Cenchrus clandestinus), forage peanut (Arachis pintoi), and white clover (Trifolium repens L.). The hypothesis is that nitrogen fertilization management in cool season pastures has a legacy effect on forage production in warm season pastures.

Understanding the coexistence and productive dynamics of Cynodon spp. and Cenchrus clandestinus grown in association

Biodiverse ecosystems present a promising alternative to the monocultures commonly used in pastoral systems. These systems can combine plants with distinct functionalities, or even those within the same functional group but with unique singular characteristics, offering sustainability with productive efficiency for both animals and plants. Additionally, they provide numerous other benefits to the system as a whole. The primary modulators of production in such arrangements are grazing management and nitrogen fertilization, which influence the response patterns of individual plants and the community of selected plants. Thus, the objective of this study is to determine whether fertilization strategies and rates alter the functional patterns of plants and promote differential contributions to forage accumulation in pastures composed of Cynodon spp. (Tifton 85) and Cenchrus clandestinus (Kikuyu grass). The hypotheses are: (1) regardless of fertilization in the cold season, high N rates in the warm season favor the kikuyu grass population but do not alter the differences in tissue flow dynamics between the species; (2) the greatest dry matter (DM) contribution in pastures receiving higher fertilizer rates results from the accumulation of kikuyu grass due to an increased number of individuals; and (3) regardless of warm season fertilization, ryegrass pastures with higher fertilization in the preceding cool season increase the dry matter accumulation of kikuyu grass and Tifton 85 in the subsequent fall.

The production of corn for silage on winter perennial pastures and its impact on pasture persistence

Dry matter production in winter perennial pastures during the warm season faces several challenges that limit forage availability and quality. These challenges are primarily related to adverse climatic conditions, the physiological characteristics of the plants, and inadequate management practices. During the warm season, high temperatures and reduced water availability, due to increased evapotranspiration, are critical factors that negatively impact the growth of winter perennial plants. Including corn silage (Zea mays) in the cropping system can be an effective solution to mitigate these challenges, as corn is a highly productive crop, well adapted to high temperatures, and highly efficient in water and nutrient use. Thus, the objective of this study is to measure the productive increment resulting from the inclusion of corn silage in winter perennial pastures, as well as to evaluate its effect on the composition and mass production during the cold season, with the hypothesis is that dry matter production during the warm season is higher with the inclusion of corn silage.

Exploring the forage potential of minor grassland species grown in pure

Stands or multispecies swards

Project in partnership with the Georg-August Univeristät Gottingen

This project has as overall objective ofthe project to determine whether plants from different agricultural groups (legume, grass, forb) can together form a productive and high-quality grassland or not. Also, to determine how the forage potential of plant will be affected by one and more cultivars and different sowing treatment.

With the following hypotheses and specific questions to be tested: Mixtures are more productive than spatial monocultures because offacilitation through biological N fixation of legumes (we used N input for non-legumes), within species diversity improves biomass production (more cultivars), spatial monocultures improve proportion of subordinate species in the pasture (e.g. Lotus corniculatus), forage quality ofthe sward is improved in mixtures.