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Crop irrigation requirements are usually estimated based on crop evapotranspiration (ETc) as determined by the reference evapotranspiration (ETo) and crop coefficient (Kc). There is a lack of knowledge on the irrigation requirements of tropical forage crops in Brazil, contrasting with the increasing use of irrigation in pastures. The effort of this study was to investigate what would be the water needs of tropical forages in Southern Brazil, based on a robust experimental database. The study was carried out in São Paulo State-Brazil using different forages species and their combinations [Guinea grass (GG); Guinea grass + black oat + ryegrass (GOR); Bermuda grass (BG), and Bermuda + black oat + ryegrass (BOR)]. The experimental fields were fully irrigated, and the Kc values were derived from ETc measurements on lysimeters; ETo was estimated using daily data from a nearby weather station and the standard FAO56 parameterization. Mean daily ETc values for GG, GOR, BG and BOR were 4.1, 2.9, 3.6, and 3.4 mm, respectively, and respective mean Kc values were 0.99, 0.90, 1.0, and 0.94. Average Kc values for all plots decreased as ETo increased, producing a negative Kc-ETo relationship, mainly when ETo reached values greater than 5 mm d−1. This was most likely due to internal plant stomatal resistance to vapor release from the leaves diffusing to the atmosphere at high ETo. So, the time-based Kc curves described by FAO 56 manual should be adjusted for the analyzed crops considering different ranges of ETo to improve the required irrigation depth. [ABSTRACT FROM AUTHOR]

The fertilization in rangelands has a positive effect in the forage production. The increased nitrogen (N) availability improves plant growth and forage quality of native pastures. However, in the Pampa biome conditions of Rio Grande do Sul State, Brazil, these responses occur surprisingly fast and consistently. Therefore, the objective of this work was to quantify the N effect in the botanical composition of a natural pasture overseeded with annual ryegrass in Southern Brazil. The effects of three rates of N fertilization (zero, 100 and 200 kg N ha-1) were evaluated. Forage biomass was estimated on a monthly basis using the double sampling approach. The different botanical components of each forage sample were manually sorted in the laboratory. In order to calculate the Rényi diversity profile, two floristic composition evaluations were performed in the experimental area in December of 2010 and September of 2011. The ryegrass biomass production is highly affected by the N fertilization. The botanical composition of natural pastures modifies most probably by increasing ryegrass competition at early spring. [ABSTRACT FROM AUTHOR]

Due to the genetic improvement of soybean cultivars more adapted to lowlands and to new drainage technologies, there has been a great insertion of soybean cultivation in rotation with irrigated rice in South America. Soybean has innumerable features beyond the fact that it is a legume, which can directly impact the microbial activity and diversity of the soil and the development of crops established in succession. Therefore, the objective was to evaluate nitrogen (N) dynamics, extracellular enzyme activity, soil microbial community, and the subsequent development of ryegrass in a Gleysol cultivated with irrigated rice and soybean in an area with a long history of irrigated rice cultivation. The experiment was conducted in the crop season 2015/16 at the Rice Research Station, Rio Grande do Sul, Southern Brazil, in an area that had been cultivated for 70 years with irrigated rice. The treatments used are irrigated rice cultivation and soybean in randomized blocks with 4 replicates. Hydrolysis of fluorescein diacetate, acid phosphatase, urease and β-glucosidase were evaluated. Bacterial communities were estimated in soil by extracting DNA and sequencing the V3-V4 region of the 16S rRNA gene. Ryegrass dry biomass was quantified after irrigated rice and soybean. Greater mineral N availability (+ 49%), higher extracellular enzyme activity (+ 51%) and microbial diversity (+ 7%) were observed after soybean cultivation compared to irrigated rice. These changes, after soybean cultivation, had a direct impact on the development of ryegrass plants, which showed higher ryegrass dry biomass production. Thus, the adoption of soybean rotation in areas traditionally cultivated with irrigated rice is an important agronomic strategy to increase the sustainability of agriculture, since it allows the increase of soil quality and availability of nutrients in lowland crop production systems. • Soybean cultivation increased nitrogen availability by 49% and enzyme activity by 51%. • Soil microbial diversity increased by 7% with soybean cultivation. • The development of ryegrass tripled in succession to soybean compared to rice. [ABSTRACT FROM AUTHOR]

The objective in this study was to characterize the productive potential, monthly yield distribution, and forage plantpart and botanical composition of black oats and annual ryegrass under harvest strategies in São Paulo. The experimental design was completely randomized with treatments corresponding to the combination among stand composition (exclusive oats, exclusive annual ryegrass, or oats + ryegrass, O+R) and harvest strategies (at 95% LI or every 30 days of regrowth, FIXED), in a factorial arrangement with three replications. Stands managed by LI accumulated 1580kg DM ha-1 harvest-1, and those managed by FIXED 2020kg DM ha-1 harvest-1. Leaf proportion was higher in ryegrass (70%), followed by O+R (64%) and oat (52%). Swards managed by LI had higher proportion of leaves and less stem than those harvested at FIXED intervals. The proportion of ryegrass was higher under the LI management (64%), than under the FIXED (70%). Over time there was the replacement of oats by ryegrass in the mixed canopy composition. Exclusive ryegrass stands are recommended. Both harvest strategies can be adopted for these winter forages in integrated systems of agriculture and livestock. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the practical application of herbicide, overseeded annual ryegrass for the establishment of forage peanut (Arachis pintoi) in natural vegetation. The experiments was conducted from October 2007 to November 2008, Estação Experimental Terras Baixas (ETB) - Embrapa Clima Temperado, Capão do Leão - RS. The treatments were arranged in a randomized block design in split plots with four replications. The plots were represented by the treatments with and without herbicide (3L ha-1 of commercial herbicide glyfosate). The subplots were defined by the absence of forage peanut, the presence of forage peanut, the presence of forage peanut overseeded with annual ryegrass. The frequencies of species of natural vegetation were not influenced by grazing and overseeded ryegrass. The establishment of forage peanut Arachis pintoi is benefited by the herbicide. However, it is a practice that causes a significant reduction of species of forage interest. The presence of annual ryegrass provides a favorable environment for forage peanut during the cool season. [ABSTRACT FROM AUTHOR]

In order to evaluate the satellite image patterns between such cool season cereals cultivated areas intended for grazing or grain production, Normalized Difference Vegetation Index (NDVI) temporal profiles were analyzed. This data was acquired from twenty nine wheat and annual ryegrass cultivated areas in the states of Rio Grande do Sul and Paraná. For each area, the cultivated species (wheat or ryegrass), as well as the respective central point coordinates, acquired via Global Positioning System (GPS) was informed. NDVI values were extracted over each monitored area from MODIS (Moderate Resolution Imaging Spectroradiometer) sensor images, with spatial resolution of 250 meters. The NDVI temporal profiles showed that grain production areas have a typical agricultural field spectral pattern. The same pattern was not observed for the grazing pasture areas. The differences observed in these temporal patterns are defined by the changes that grazing has imposed on the phenology and morphology of these plants. [ABSTRACT FROM AUTHOR]

Ryegrass (Lolium multiflorum Lam.) is the main winter weed of crops in Southern Brazil. High competitiveness, adaptability, widespread resistance to herbicides and seed dormancy make the plant a permanent problem. Herbicides, as well as plant growth regulators, can be used as a management option for ryegrass seed production, however there is no consensus among authors at which stage of the plant the application is most effective. Thus, this study aimed to evaluate the production and physiological quality of ryegrass seeds in response to the application of herbicides and plant growth regulators in three stages of plant development (inflorescence emergence, flowering and fruit development). Each treatment consisted of applying two different doses of each of the active ingredients: ammonium glufosinate, clethodim, glyphosate, iodosulfuron-methyl, paraquat and 2,4-D (herbicides); ethephon and trinexapac-ethyl (plant growth regulators), still an untreated control, totaling 17 treatments for each stage of development. The experimental design used was randomized blocks, with three replications. The variables evaluated were: seed production (kg ha−1), thousand seed weight (g), viability (%), germination (%), first germination count (%), dormant seeds (%) and dead seeds (%). The ryegrass seed production reduced 100% with clethodim, glyphosate, ammonium glufosinate or paraquat applied in the inflorescence emergence or flowering stages. In the fruit development stage, all treatments (herbicides and plant growth regulators) caused deleterious effects on seed production, the greatest effect occurred with paraquat (95%). Paraquat, ammonium glufosinate and clethodim affected the physiological quality of the seeds when applied in fruit development stage. This research demonstrated that the application of herbicides in the ryegrass reproductive stage decreases its seedbank replenishment (natural re-sowing), with the potential to harm its progeny. [ABSTRACT FROM AUTHOR]