Fernando Campos Mendonça

Dry matter production of Tanzania grass as a function of agrometeorological variables

o 11, CEP 13418‑900 Piracicaba, SP, Brazil. E‑mail: fcmendon@esalq.usp.br, lc_araujo@yahoo.com.br Abstract - The objective of this work was to develop and validate linear regression models to estimate the production of dry matter by Tanzania grass (Megathyrsus maximus, cultivar Tanzania) as a function of agrometeorological variables. For this purpose, data on the growth of this forage grass from 2000 to 2005, under dry‑field conditions in Sao Carlos, SP, Brazil, were correlated to the following climatic parameters: minimum and mean temperatures, degree‑days, and potential and actual evapotranspiration. Simple linear regressions were performed between agrometeorological variables (independent) and the dry matter accumulation rate (dependent). The estimates were validated with independent data obtained in Sao Carlos and Piracicaba, SP, Brazil. The best statistical results in the development and validation of the models were obtained with the agrometeorological parameters that consider thermal and water availability effects together, such as actual evapotranspiration, accumulation of degree-days corrected by water availability, and the climatic growth index, based on average temperature, solar radiation, and water availability. These variables can be used in simulations and models to predict the production of Tanzania grass.

Development of maize and palisadegrass plants cultivated in intercrop under water deficit

The objective of this work was to evaluate the development and productive traits of palisadegrass single cultivated or intercropped with corn, in addition to corn intercropped with pasture, under water deficit at different development stages of the plants. It was used a complete block experimental design with split plots and three replicates. Periods of water deficit were placed in the plots and types of cultivation were placed in the subplots. Irrigation was stopped at germination and initial tillering of palisadegrass and at V4 and V15 stages of corn and returned when soil moisture was 40% of available water capacity. Tiller density and palisadegrass height were evaluated weekly. Dry matter (DM) of fractions of herbage mass as well as leaf area of the plants were evaluated at corn tasseling and when grains reached physiological maturity. Components of corn production were determined in the second sampling. In palisadegrass, water influenced only tillering, which was reduced in the plots in which water defict was forced at the moment of germination or at the beginning of tilering, in both cultivation systems. Plant height and DM production were affected only by cultivation, reducing when intercropped with corn. Evaluated production components did not influence corn grain productivity, which was similar in all treatments (average of 10,145 kg/ha). Palisadegrass plants produce more DM in single cultivation than intercropped with corn. Water deficit during germination and initial tillering reduces tillering of palisadegrass during establishment phase. Water deficit, applied in this trial, does not reduce DM yield in palisadegrass or corn.

Adubação nitrogenada do milho em um sistema de irrigação por aspersão em linha

Foi avaliado o efeito do nitrogenio na cultura do milho atraves da fertirrigacao, utilizando um sistema de irrigacao por aspersao em linha e ureia como fonte de N. O sistema de aspersao em linha foi constituido por 3 linhas com cinco aspersores cada uma, cujo espacamento foi de 6 metros entre si e 12 metros entre as linhas. O fertilizante foi aplicado nas linhas externas e a linha central aplicou apenas agua. A lâmina de agua total aplicada durante o ciclo foi de 650 mm. Essa aplicacao foi feita de forma uniforme, e as doses de nitrogenio foram decrescentes na direcao perpendicular as linhas externas de aspersores, variando de 353 a 30 kg/ha de N. Os resultados obtidos mostraram que as diferentes dosagens de nitrogenio afetaram os seguintes parâmetros medidos: altura das plantas, altura de insercao das espigas, produtividade, comprimento das espigas, peso de mil graos e teor de nitrogenio nos graos. O ponto de maxima produtividade de graos (7634 kg/ha) foi estimado atraves de uma funcao de producao da cultura em relacao ao fator doses de nitrogenio. A maxima produtividade estimada pode ser atingida com uma dose de 262,6 kg/ha de N.

Establishment of Brachiaria brizantha cv. Marandu, under levels of soil water availability in stages of growth of the plants

The objective of this work was to evaluate yield traits and development of palisadegrass under the influence of water deficit during the establishment period. The experiment was carried out in a greenhouse, in a completely random block statistical design in a factorial arrangement and additional treatment (3 × 3 + 1). The treatments referred to the suppression of irrigation at different phases of the establishment (sowing, germination and initial tillerring) until the soil presented water content of 75%, 50%, and 25% of the moisture related to field capacity (qFC), besides control treatment with no water restriction. Evaluations of number of grown tillers per vase, green leaves per tiller and plant height were carried out weekly, for five weeks after the first tillers appeared. Biomass sampling was carried out approximately 30 days after the end of the last applied treatment, when the soil was kept close to 100% of field capacity relative moisture. Tillering and biomass yield of palisadegrass during establishment phase are reduced when water deficit is sufficient to make soil content water reach 25% of relative moisture field capacity, regardless to the season when water shortage takes place.

Critical periods of sorghum and palisadegrass in intercropped cultivation for climatic risk zoning

The objective of this work was to define critical periods for sorghum and palisadegrass cultivated on crop-livestock integrated systems under water deficit. An experiment was carried out in a completely random block design with four treatments (control and interruption of water supply in three periods) and three replicates. Water supply was interrupted until soil water humidity was close to permanent wilting point at the phases: germination of palisadegrass seeds; start of tillering of palisadegrass and initiation of panicles of shorghum; start of shorghum flowering. Water deficit starting at palisadegrass germination delayed intital development of the plants because of the reduction in tillering. Water restriction at panicle initiation phase and at sorghum flowering determined reduction of grain production. Critical periods for intercrop of sorghum and palisadegrass correspond to palisadegrass germination phase and flowering and panicle inititation phase of sorghum.

Comparison of water consumption estimate for Urochloa brizantha cv. Marandu with FDR probe and weighting lysimeter.

Capacitive probes are devices with high investment costs, but they have the advantage of mobility and practical use compared with lysimeters. Therefore, studies are needed to verify the use of this technique in the determination of water consumption by forage plants. The objective of this work was to evaluate the use of a capacitive probe to estimate the water consumption in two cropping systems compared to the data obtained by the weighing lysimeter. They were: single (Marandu palisadegrass) and consortium (Marandu palisadegrass+ black oats + ryegrass). The study was carried out in an experimental area of ESALQ/USP. Data from six cycles of Marandu palisadegrass development were used, four in exclusive cultivation and two in consortium cultivation. Soil moisture was evaluated by the Diviner® capacitive probe and used to calculate the soil water balance. The coefficient of culture data (Kc) estimated by the capacitive probes were correlated with those determined in the weighing lysimeters, correlations were significant (p<0,05) and linear equations. The estimates made with the probe differed from those made with lysimeters overestimating 78% of the studied cases, Kc values of the probes in relation to lysimeters.

Productivity and nutritional quality of Urochloa brizantha cv. BRS Piatã grass fertirrigated with swine wastewater in different seasons of the year

The Brazilian swine production has been grown 38.9% in the last decade. Inherent to the process, the pollution potential has increased which brings environmental concerns, especially about the final disposal of swine wastewater (SW). In this context, this work aimed to evaluate the responses of ‘Piatã’ grass (Urochloa brizantha, cv. BRS ‘Piatã’) to the fertilization with SW, with and without supplemental irrigation. The experiment was carried out for one year from March 2014 to March 2015. The experiment was conducted in a split-plot with a random blocks experimental design with four replications. The treatments in the plots were referred to the use of irrigation (with and without), and in the subplots to the SW doses (four doses: 75, 150, 225 and 300 m ha). In the irrigated treatment, the irrigation was fulfilled to re-establish soil moisture in the field capacity (Өfc). The parameters used to verify the treatments were: total forage yield (TFY), leaves and stems yield (LSY), crude protein rate (CP), neutral detergent fibre (NDF), acid detergent fibre (ADF) and in vitro dry matter digestibility (DivDM). There was a significant increasing effect for doses, reaching a mean TFY of 41.92 Mg ha at the dose of 300 m ha. The combination of the highest dose of SW combined with supplemental irrigation produced the best results of TFY and LSY with (47.8 and 41.9 Mg ha year, respectively). Irrigation also led to the best results per cycle, with the highest forage accumulation in spring, 12.28 and 8.55 Mg ha for irrigated and non-irrigated treatments, respectively. In the bromatological parameters, supplemental irrigation led to the highest average levels of CP, ADF and DivDM of 16.7%, 33.8% and 66.5%, respectively. The NDF did not respond to irrigation and SW doses. The research allowed concluding that irrigation and SW fertigation brought quantitative and qualitative benefits to ‘Piatã’ grass production.