Abstract The utilization of wastewater from livestock farming (WLF) represents a common agricultural practice, but the absence of research on its agronomic impacts hinders its sustainable implementation. This study assesses the reutilization of WLF combined with nitrogen fertilization on the morphological, bromatological, and productivity attributes of a Tifton 85 pasture during the winter season. The study involved the application of different types of water via sprinkler: (I) stream water; (II) mixture of WLF and stream water at a 1:1 ratio; and (III) undiluted WLF combined with mineral nitrogen fertilization (0 and 45 kg N ha-1) administered at the commencement of the regrowth period. Irrigation was applied on a weekly basis, totaling 2,440 m3 ha-1. At 106 days post-regrowth, parameters including forage productivity, height, leaf-stem ratio, leaf area index, nitrogen nutrition index, crude protein content, acid detergent fiber, neutral detergent fiber, and mineral matter content were determined. Mineral fertilization at the prescribed dosage (45 kg N ha-1) did not have any discernible impact on the parameters under investigation. On average, the reuse of WLF raised the productivity from 2.50 to 5.12 t ha-1 and the Crude Protein from 12.35% to 14.58% compared to stream water. The reuse of WLF demonstrated superior outcomes (p < 0.01) in terms of pasture productivity, nutritional quality, and nitrogen accumulation compared to irrigation solely with stream water. The reuse of diluted WLF (1:1) without fertilization proved adequate to sustain Tifton 85 pastures during the winter season in the Brazilian Cerrado region. (WLF practice implementation morphological bromatological 8 sprinkler I (I II (II 11 1 1: ratio III (III 0 ( 4 ha1 ha period basis 2440 2 440 2,44 m ha1. 1. 10 postregrowth, postregrowth post regrowth, post-regrowth height leafstem stem index fiber determined (4 investigation average 250 50 2.5 512 5 12 5.1 ha- 1235 35 12.35 1458 14 58 14.58 p 0.01 001 01 quality (1:1 region 244 44 2,4 25 2. 51 5. 123 3 12.3 145 14.5 0.0 00 (1: 24 2, 12. 14. 0. (1

Resumo A aplicação de águas residuárias da bovinocultura (ARB) é uma prática usual, entretanto, carece de investigação acerca dos seus efeitos agronômicos para subsidiar a sua utilização sustentável. O objetivo deste estudo foi avaliar o reúso da ARB e da adubação mineral nitrogenada sobre os atributos morfológicos, bromatológicos e de produtividade da pastagem de Tifton 85 durante o inverno. Foram avaliados diferentes tipos de água aplicados por aspersão (I - água de córrego, II - ARB e água de córrego em proporção 1:1, e III - ARB) e dois níveis de adubação nitrogenada mineral (0 e 45 kg N ha-1) aplicados no início da rebrota. A irrigação foi semanal e totalizou 2.440 m3 ha-1. Aos 106 dias após a rebrota foram medidas a produtividade da forrageira, altura, razão folha/colmo, índice de área foliar, índice de nutrição de nitrogênio, proteína bruta, fibras insolúveis em detergente ácido, fibras insolúveis em detergente neutro e matéria mineral. A adubação mineral na dose de 45 kg N ha-1 não influenciou as variáveis avaliadas. Em média, o reúso da ARB elevou a produtividade de 2,50 para 5,12 t ha-1 e a proteína bruta de 12,35% para 14,58% comparado com a água de córrego. O reúso da ARB com ou sem diluição proporcionou produtividade, qualidade nutricional e acúmulo de nitrogênio pela pastagem superiores à irrigação com apenas água de córrego (p < 0,01), sendo o reúso com ARB diluída (1:1) e sem adubação é suficiente para sustentar a pastagem de Tifton 85 durante o inverno no Cerrado. (ARB usual entretanto sustentável morfológicos 8 I 11, 11 1 1, 1:1 0 ( 4 ha1 ha 2440 2 440 2.44 m ha1. 1. 10 forrageira altura folhacolmo folha colmo folha/colmo foliar ácido ha- avaliadas média 250 50 2,5 512 5 12 5,1 1235 35 12,35 1458 14 58 14,58 p 0,01, 001 0,01 , 01 0,01) (1:1 Cerrado 1: 244 44 2.4 25 2, 51 5, 123 3 12,3 145 14,5 00 0,0 (1: 24 2. 12, 14, 0, (1

Resumen Introducción. La alimentación de los animales en los sistemas ganaderos del trópico alto colombiano se basa en el pastoreo de gramíneas en monocultivo de baja calidad y biomasa en los periodos de sequía, lo que afecta el desempeño productivo de los animales. Objetivo. Evaluar la producción y la calidad nutricional del forraje de Sambucus nigra L., establecido como un arreglo silvopastoril de cercas vivas. Materiales y métodos. La investigación se desarrolló en la finca San Joaquín, ubicada en Paipa, Colombia; los muestreos se realizaron entre enero 2019 y marzo 2020. En un arreglo de cercas vivas se seleccionó un transecto de 226 m lineales, en los que se escogieron al azar diecisiete árboles. Se evaluó la producción de forraje verde y materia seca de la planta completa y sus fracciones (hojas y tallos), la relación hoja – tallo y la calidad nutricional (NIRS) de la planta completa y de cada fracción. Se utilizó un diseño completamente al azar, se realizó estadística descriptiva y análisis de varianza no paramétrica (prueba de Kruskal Wallis) para producción de forraje y relación hoja-tallo, el análisis de los datos se hizo mediante el programa Infostat®. Resultados. La producción de forraje verde y materia seca fue de 19,8 t km-1 año-1 y 3,9 t km-1 año-1, respectivamente. Se presentaron diferencias (p<0,0001) en la calidad nutricional, las hojas presentaron mayor calidad, el forraje presentó altos contenidos de proteína cruda, energía metabolizable y digestibilidad, bajo porcentaje de fibra en detergente neutro y fibra en detergente ácido, la relación hoja-tallo fue de 0,8:1, aunque se presentaron diferencias entre muestreos (p<0,0001). Conclusiones. Las cercas vivas de Sambucus nigra generaron alta producción de biomasa comestible por kilómetro al año, el forraje de la planta completa y sus fracciones tuvieron buena calidad nutricional, especialmente proteína cruda, energía y digestibilidad.

Abstract Introduction. Livestock feeding in Colombian high tropic livestock systems is based on monoculture grass grazing of low quality and low biomass during drought periods, which affects the productive performance of the animals. Objective. To evaluate the production and nutritional quality of forage of Sambucus nigra L., established as a silvopastoral live fence arrangement. Materials and methods. The research was carried out at the San Joaquin farm, located in Paipa, Colombia; the samplings were done between January 2019 and March 2020. In a live fence arrangement, a 226 m linear transect was selected, in which 17 trees were randomly selected. The green forage and dry matter production of the complete plant and its fractions (leaves and stems), the leaf - stem ratio and the nutritional quality (NIRS) of the complete plant and of each fraction were evaluated. A randomized design was carried out, descriptive statistics and analysis of non-parametric variance (Kruskal Wallis test) were performed for forage production and leaf-stem relationship, the data analysis was done using the Infostat® program. Results. The production of green forage and dry matter was 19, t km-1 year-1 and 3,9 t km-1 year-1, respectively. There were differences (p<0.0001) in nutritional quality, the leaves were of higher quality, the forage had a high crude protein content, metabolizable energy and digestibility, low percentage of neutral detergent fiber and acid detergent fiber, the leaf-stem ratio was 0.8: 1, although there were differences between samplings (p<0.0001). Conclusions. The living fences of S. nigra produced high production of edible biomass per kilometer per year, the forage of the complete plant and its fractions had good nutritional quality, crude protein, energy, and digestibility.

RESUMEN Con el objetivo de determinar el momento óptimo de cosecha del kikuyo (Cenchrus clandestinus (Hochst. ex Chiov.) Morrone) de acuerdo al número de hojas por rebrote y la fertilización nitrogenada, se realizó un experimento bajo invernadero con un diseño factorial 4×4. Los factores fueron el número de hojas por rebrote a la cosecha (3, 4, 5, 6 hojas) y el nivel de fertilización nitrogenada (0, 50, 100, 150 kg de N ha-1 año-1). Se determinó el rendimiento de materia seca (MS) y la calidad nutricional. Adicionalmente, se evaluó el efecto de la fertilización nitrogenada sobre la altura sin disturbar y el filocrono. Al aumentar el número de hojas por rebrote (3 a 6) aumentó (P<0,05) el rendimiento de hojas y el material muerto y disminuyó la relación material verde-muerto (P<0,05). La relación hoja-tallo fue constante entre número de hojas (P>0,05). Hubo menores concentraciones de proteína cruda (PC) y mayores concentraciones de fibra en detergente neutro (FDN) (P<0,05) a mayor número de hojas. La fertilización nitrogenada aumentó la altura sin disturbar, la densidad de estolones, la producción de MS, la relación forraje vivo-forraje muerto, la PC en hojas y disminuyó el FDN (P<0,05). El filocrono fue mayor (P<0,05) cuando no se fertilizó. Los efectos del número de hojas por rebrote y la fertilización nitrogenada fueron independientes para la mayoría de las variables. Sin embargo, debido al incremento en el rendimiento de MS por la fertilización N, la pastura puede ser defoliada con menor número de hojas por rebrote, aumentando la frecuencia de defoliación y mejorando la calidad del forraje.

ABSTRACT To determine the optimum harvest time of kikuyu grass (Cenchrus clandestinus (Hochst. ex Chiov.) Morrone), according to the number of leaves per tiller and nitrogen fertilization level, an experiment was carried out under greenhouse conditions using a 4×4 factorial design. The factors were the number of leaves per tiller (3, 4, 5, 6 leaves) and level of nitrogen (N) fertilization (0, 50, 100,150 kg of Nitrogen ha-1 year-1). Dry matter (DM) yield and nutritional quality were determined. Additionally, the independent effect of nitrogen fertilization on undisturbed height, tiller density, and the phyllochron were evaluated. When the number of leaves per tiller increased (3 to 6), the leaf yield and dead forage also increased (P<0.05). The leaf-stem ratio (L:S) remained constant (P>0.05) among the number of leaves. Green forage-dead forage ratio (GF:DF) decreased (P<0.05) with a higher number of leaves per tiller. The concentration of crude protein (CP) decreased while the concentration of neutral detergent fiber (NDF) increased with an increment of the number of leaves per tiller (P<0.05). Nitrogen fertilization increased the undisturbed height, the density of tillers, DM yield from leaves, stems and green forage, GF:DF, and CP (P<0.05) while NDF decreased (P<0.05). The phyllochron was higher without N fertilization. The effects of the number of leaves per tiller and N fertilization on the most variables measured were independent of each other. However, due to an increment in DM yield caused by N fertilization, the pasture can be defoliated with fewer leaves per tiller, increasing defoliation frequency and improving forage quality.

Abstract The objective was to determine the effect in cut-off intervals on dry matter yield, leaf-stem ratio, protein and digestibility in situ in the leaf and stem of alfalfa cv ‘San Miguelito’, in the Mexican Altiplano. Four cut intervals (3, 4, 5 and 6 weeks for spring-summer and 4, 5, 6 and 7 weeks for autumn-winter) were randomly distributed under a completely randomized experimental design, with 4 repetitions. The intervals of 6 and 7 weeks (p< 0.05), produced the highest yield of dry matter per cut with 4 393 kg DM ha-1; however, they also obtained the lowest values of leaf-stem ratio (0.74), leaf and stem protein (26.9 and 11.7%) and leaf and stem digestibility (79.8 and 64.3%). In order to obtain an appropriate balance between yield and forage quality, it is concluded that alfalfa must be harvested, at cut-off intervals of six weeks in autumn and winter, four weeks in spring and five weeks in summer.

Resumen El objetivo fue determinar el efecto en intervalos de corte sobre el rendimiento de materia seca, relación hoja-tallo, proteína y digestibilidad in situ en hoja y tallo de alfalfa cv ‘San Miguelito’, en el Altiplano Mexicano. Se establecieron cuatro intervalos de corte (3, 4, 5 y 6 semanas para primavera-verano y 4, 5, 6 y 7 semanas para otoño-invierno) distribuidos aleatoriamente bajo un diseño experimental completamente al azar, con 4 repeticiones. Los intervalos de 6 y 7 semanas (p< 0.05), produjeron el mayor rendimiento de materia seca por corte con 4 393 kg MS ha-1; sin embargo, también obtuvieron los menores valores de la relación hoja-tallo (0.74), proteína en hoja y tallo (26.9 y 11.7%) y digestibilidad en hoja y tallo (79.8 y 64.3%). Con la finalidad de obtener un balance apropiado entre rendimiento y calidad del forraje se concluye que la alfalfa se debe cosechar, a intervalos de corte de seis semanas en otoño e invierno, de cuatro semanas en primavera y de cinco semanas en verano.

Abstract: Gamma radiation can be utilized as a mutagenic agent for inducing genetic variability in plant species. However, the adequate dose of radiation must be established before starting a mutagenesis-based breeding program. The objective was to determine the mean lethal dose (LD50) and the dose for the mean growth reduction (GR50) in Wilman lovegrass (Eragrostis superba Peyr.). For this purpose, the seeds were radiated with doses of 0 (control treatment), 100, 200, 300, 450, 600, 900, 1400, 2000 and 4000 Gray. The evaluated variables were germination percentage, germination speed index, plumule length, radicle length, forage yield, seed production, leaf-stem ratio and chlorophyll concentration index. The data were analyzed through regression analyses and the Dunnett’s mean comparison test. The LD50 and GR50 generated for each of the evaluated variables were calculated with the resulting regression equation. Based on the values of LD50 and GR50, a weighted mean was estimated; the LD50 was weighted with 30 % while the GR50 with 10%. In general, all the evaluated characteristics were affected by the radiation treatment (P<0.05), and their behavior was adjusted to linear square models (P<0.05), allowing the determination of the LD50 and the GR50. The weighting average of both parameters, estimated at 2486 Gy, is recommended for the genetic breeding of Wilman lovegrass. The results of this study will allow implementing mutagenesis-based plant breeding programs in Wilman lovegrass.

Resumen: La radiación gamma puede ser utilizada como agente mutagénico para inducir variabilidad genética en especies vegetales. No obstante, antes de comenzar un programa de mejoramiento mediante mutagénesis, es necesario establecer la dosis de irradiación adecuada. El objetivo fue determinar la dosis letal media (DL50) y de reducción media del crecimiento (RC50) en pasto garrapata (Eragrostis superba Peyr.). Para ello, se irradió semilla con dosis de 0 (tratamiento testigo), 100, 200, 300, 450, 600, 900, 1400, 2000 y 4000 Gray. Las variables evaluadas fueron porcentaje de germinación, índice de velocidad de germinación, longitud de plúmula, longitud de radícula, rendimiento de forraje, producción de semilla, proporción hoja-tallo e índice de concentración de clorofila. Los datos se analizaron por regresión y comparación de medias con la prueba de Dunnett. Con la ecuación de regresión resultante se calculó la DL50 y RC50 para cada variable. Con estos valores se obtuvo una media ponderada, donde la DL50 se ponderó con 30 % y las RC50 con 10 %. En general, todas las características evaluadas se vieron afectadas por la irradiación (P<0.05), y su comportamiento se ajustó a modelos lineales y cuadráticos (P<0.05), lo cual permitió determinar la DL50 y las RC50. Para el mejoramiento genético del pasto garrapata, se recomienda utilizar la ponderación de ambos parámetros, la cual se obtuvo a los 2,486 Gy. Los resultados de este estudio permitirán la implementación de programas de mejoramiento genético por mutagénesis en pasto garrapata.

Abstract: Three herbaceous legumes: Macroptilium atropurpureum, Macroptilium lathyroides and Phaseolus acutifolius were sown in 12 experimental units of plots of 28 m2 each under a randomized complete block design with four replications. The objective was to evaluate the characteristics of dry matter (DM) production, leaf-stem ratio and coverage, as well as the concentration of crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), lignin (LDA), tannins, phenols and in vitro digestibility of DM (IVDDMS) throughout the biological cycle of the species. The average DM production (kg ha-1) differed (P<0.05) among species, being higher for M. lathyroides (4,655), intermediate for M. atropurpureum (3,920) and lower (2,170) for P. acutifolius. The difference in DM production between M. lathyroides and M. atropurpureum was mainly a reflection of differences in plant height rather than differences in the leaf-stem ratio or coverage. M. lathyroides and M. atropurpureum were not different (P>0.05) in CP concentration, NDF, ADF and IVDDMS. The species P. acutifolius showed the lowest concentration of all the fractions including DIVMS. The concentration of tannins (g kg-1 MS) was high (P<0.05) for M. lathyroides (3.93), intermediate for M. atropurpureum (3.14) and low (1.82) for P. acutifolius. In phenols, the species were not different, having an average of 20.3 g kg-1 DM. It is concluded that M. lathyroides and M. atropurpureum were the species with the best yield performance and nutritional quality in the total experimental phase.

Resumen: Tres leguminosas herbáceas: Macroptilium lathyroides, Macroptilium atropurpureum y Phaseolus acutifolius se sembraron en 12 unidades experimentales de 28 m2 cada una, bajo un diseño de bloques completos al azar y cuatro repeticiones por especie. El objetivo fue evaluar las características de producción de materia seca (MS), relación hoja-tallo y cobertura, así como la concentración de proteína cruda (PC), fibra detergente neutro (FDN), fibra detergente ácido (FDA), lignina (LDA), taninos, fenoles y digestibilidad in vitro de la MS (DIVMS) en todo el ciclo biológico de las especies. La producción promedio de MS (kg ha-1) difirió (P<0.05) entre especies, resultando mayor para M. lathyroides (4,655), intermedia para M. atropurpureum (3,920) y menor (2,170) para P. acutifolius. La diferencia en producción de MS entre M. lathyroides y M. atropurpureum fue un reflejo principalmente de diferencias en la altura de la planta, más que a diferencias en la relación hoja-tallo o cobertura. M. lathyroides y M. atropurpureum no fueron diferentes (P>0.05) en concentración de PC, FDN, FDA y DIVMS. La especie P. acutifolius mostró una menor concentración de todas las fracciones y una menor DIVMS. La concentración de taninos (g kg-1 MS) fue mayor (P<0.05) para M. lathyroides (3.93), intermedia para M. atropurpureum (3.14) y menor (1.82) para P. acutifolius. En fenoles, las especies no fueron diferentes, obteniendo un promedio de 20.3 g kg-1 MS. Se concluye que M. lathyroides y M. atropurpureum fueron las especies con mejor comportamiento productivo y calidad nutritiva en toda la fase experimental.

RESUMO: O presente trabalho avaliou o efeito de períodos crescentes de convivência com plantas daninhas sobre os componentes nutricionais da gramínea forrageira Brachiaria brizantha cv. Marandu em condições de renovação de pastagem. O experimento foi instalado no delineamento experimental de blocos casualizados com quatro repetições, e os tratamentos foram representados por oito períodos de convivência com as plantas daninhas: 0, 15, 30, 45, 60, 75, 90 e 120 dias após a emergência. Foi realizada avaliação fitossociológica na comunidade infestante ao término de cada período de convivência; posteriormente, as plantas daninhas foram eliminadas com o auxílio de herbicida formulado à base de aminopyralid+2,4-D (40+320 g L-1) em pós-emergência. As forrageiras foram avaliadas ao final do período experimental quanto à relação entre matéria seca de folha e colmo, densidade volumétrica de folha verde, densidade volumétrica de matéria seca total e quanto aos principais componentes nutricionais, a saber: teor de proteína bruta, fibra em detergente neutro, extrato etéreo, matéria orgânica e matéria mineral, sendo determinado o teor de carboidratos totais. A presença das plantas daninhas alterou a estrutura da pastagem, uma vez que interferiu negativamente na relação folha/colmo e na densidade volumétrica de folhas verdes de B. brizantha. A convivência com as plantas daninhas também reduziu proporcionalmente o valor nutricional de todos os componentes nutricionais de B. brizantha conforme aumentou o período de convivência e determinou que o controle deva ser adotado antes de 30 dias de convivência entre a forrageira e as plantas daninhas.

ABSTRACT: This research aimed at evaluating the effect of increasing coexistence periods with weeds on the nutritional components of the forage grass Brachiaria brizantha cv. Marandú under pasture renewal conditions. The experiment was arranged in randomized blocks with four replications, and treatments were represented by eight coexistence periods, namely: 0, 15, 30, 45, 60, 75, 90 and 120 days after seedling emergence. A phytosociologic evaluation was performed on the weed community at the end of the coexistence periods; later, weeds were eliminated by an herbicide formulated with aminopyralid+2,4-D (40+320 g L-1) at 2.5 L ha-1, applied in post-emergence. The fodder plants were evaluated at the end of the experimental period as for leaf-stem ratio, volumetric density of green leaf, volumetric density of total dry matter and main nutritional components, including: crude protein, neutral detergent fiber, ether extract, organic matter and mineral matter, and from this, the total carbohydrate content was calculated. The presence of weeds altered the pasture structure, since it affected negatively the leaf/stem ratio and the volumetric leaf density of B. brizantha. The coexistence also reduced the nutritional components of B. brizantha and determined that control measures should be adopted before reaching 30 days of coexistence between fodder plants and weeds.

O trabalho teve como objetivo avaliar o efeito da aplicação de doses crescentes de dejeto líquido suíno sobre a produção e composição químico-bromatológica da parte aérea da aveia preta. O experimento foi conduzido em sistema de plantio direto sob o delineamento em blocos casualizados com quatro repetições e os tratamentos constituídos pela aplicação de 0; 10; 20; 30; 40 e 50 m³ ha-1 de dejeto líquido suíno. Foram determinados a produção de MS da parte aérea, a relação folha:colmo e os teores de proteína bruta (PB), fibra em detergente ácido (FDA), fibra em detergente neutro (FDN), matéria mineral (MM), matéria orgânica (MO), nitrogênio (N), fósforo (P), potássio (K), cálcio (Ca), magnésio (Mg), cobre (Cu), zinco (Zn), manganês (Mn) e ferro (Fe). A aplicação de dejeto líquido suíno não promoveu efeitos significativos sobre a produção de MS e teores de FDN, MM e MO, mas promoveu aumento linear da relação folha:colmo e do teor de PB e redução linear no teor de FDA. Quanto aos minerais, as doses de dejeto líquido suíno promoveram aumento linear nos teores de N, P, K, Ca e Zn, sem efeitos sobre os demais minerais estudados. A utilização de dejeto líquido suíno na fertilização da cultura da aveia até a dose de 50 m³ ha-1 não aumenta a produção de forragem mas eleva o valor nutricional.

The work has as objective evaluate the effect of application of increasing doses of pig slurry under yield and chemical composition of black oat shoot. The experiment was carried out in no-tillage system under experimental design of randomized blocks with four replications and the treatments composed by application of 0; 10; 20; 30; 40; 50 m³ ha-1 of pig slurry. Were determined the yield of total dry mass, the leaf-stem ratio and content of crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), mineral matter (MM), organic matter (OM), nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), copper (Cu), zinc (Zn), manganese (Mn), iron (Fe). The application of pig slurry did not promote significant effects on dry mass yield and content of NDF, MM and OM, but promoted linear increase of leaf-stem ratio and of CP and linear decrease in content of ADF. Regarding to minerals, the doses of pig slurry promoted linear increase in contents of N, P, K, Ca, and Zn, without effects on the other studied minerals. The use of pig slurry fertilization on the oat crop until the dose 50 m³ ha-1 does not increase forage production but increases the nutritional value.

Este trabalho teve como objetivo avaliar as características estruturais, morfológicas e produtivas em pastos de capim-mombaça sob lotação rotacionada com três períodos de descanso, definidos conforme o número de novas folhas expandidas por perfilho: 2,5, 3,5 e 4,5 folhas. O delineamento experimental foi inteiramente casualizado com seis repetições, num total de 18 piquetes. Foram avaliadas as características: biomassa total, taxa de crescimento cultural, altura do dossel, relação folha/colmo, índice de área foliar, interceptação da radiação, taxa de aparecimento e alongamento foliares, taxa de alongamento do colmo, densidade de perfilhos e coeficiente de extinção. As maiores taxas de acúmulo de forragem foram observadas em piquetes submetidos a período de descanso correspondente ao aparecimento de 2,5 folhas por perfilho. A menor biomassa de forragem por ciclo de pastejo deste tratamento foi compensada pelo maior número de ciclos observados. O índice de área foliar foi proporcional ao período de descanso, mas a interceptação da radiação ultrapassou o valor de 95% ao final do período de descanso em todos os tratamentos. O prolongamento do período de descanso resultou em comprometimento da estrutura do pasto, sinalizado por baixos valores da relação folha/colmo. O período de descanso em capim-mombaça não deve ultrapassar o tempo necessário para o aparecimento de três folhas por perfilho.

The objective of this work was to evaluate structural, morphological and productive traits of Panicum Maximum cv. Mombaça pasture under rotational stocking. Three rest periods defined in terms of 2.5, 3.5 and 4.5 leaves per tiller were studied. Experimental design was completely randomized with six replicates (paddocks) per treatment. Experimental variables assessed were: forage biomass, biomass accumulation rate, plant height, leaf-stem ratio, leaf area index, interception of photosynthetically active radiation (PAR), leaf appearance and elongation rates, stem elongation rate, tiller density population and extinction coeficient. Forage biomass per grazing cycle, leaf area index and plant height varied directly while tiller population, crop growth rate and leaf-stem ratio varied inversely with length of the rest period. Though leaf area index and forage biomass related directly with the duration of the rest period, interception of PAR exceeded the value of 95% by the end of rest period, regardless of experimental treatment. Rest period prolongation jeopardizes the pasture structure, which could be verified by low values of leaf/stem ratio. Rest period in Panicum maximum cv. Mombaça should not be longer than the time for the appearance of three leaves per tiller.

O trabalho foi conduzido no Município de Coronel Pacheco - MG (Embrapa Gado de Leite), com objetivo de avaliar, em condições de pastejo, o capim-estrela-africana (Cynodon nlemfuensis, Vanderyst) e três cultivares de Cynodon dactylon, L. Pers. (Florona, Florakirk, Florico), adubadas com N:K2O, nas dosagens de 250:200 ou 500:400 kg/ha/ano. O delineamento experimental foi o de blocos ao acaso, com parcelas subdivididas e três repetições. Não houve diferenças significativas nas produções de massa seca (MS) em função das dosagens de N aplicadas. Nas duas dosagens de N:K2O, a produção anual de MS da Florakirk foi a mais elevada, porém com baixa produção na época da seca. A cultivar Florico foi a de menor produção de MS. As cultivares Florona e Florakirk proporcionaram a melhor e a pior distribuição estacional de forragem, respectivamente. As doses de N:K2O e as épocas do ano não influenciaram nos teores de PB, que foram diretamente proporcionais à relação folha-colmo da planta. Os maiores teores de PB foram proporcionados pela cultivar Florakirk, enquanto os menores pelo capim-estrela-africana e cultivar Florico. A DIVMS da forragem produzida na época das chuvas foi ligeiramente superior à da época da seca. Não houve influência das dosagens de N:K2O sobre a DIVMS, que foi mais elevada na forragem produzida pelas cultivares Florakirk e Florona.

The study was undertaken in Coronel Pacheco - MG (National Dairy Cattle Reserch Center of the Brazilian Agricultural Corporation - EMBRAPA), to evaluate, under grazing conditions, the Cynodon nlenfuensis, Vanderyst and three cultivars of Cynodon dactylon, L. Pers. (Florona, Florakirk, Florico), fertilized with either 250:200 or 500:400 kg/ha/year of N:K2O. The experimental design was a randomized blocks, in split-plot, and three replications. No significant difference on dry matter yield between the two rates of N/K2O were found. In both N:K2O rates, Florakirk cultivar presented the highest annual dry matter yield, however, in the dry season it showed a low yield level. The Florico was the cultivar with the lowest dry matter yield. The best and the worst forage distribution were exhibited by cultivars Florona and Florakirk, respectively. The CP contents in the forage was not influenced by either nitrogen rates or season, and directly related to the leaf-stem ratio. The highest CP contents were found in Florakirk, while the lowest in african stargrass grass and Florico cultivar. The IVDMD of forage produced during the rainy season was slightly superior to those of the dry season. The N:K2O rates did not influence IVDMD, which were higher in Florakirk and Florona cultivars.