Joaquim Bartolomeu Rassini

Período de estacionalidade de produção de pastagens irrigadas

Abstract – This study was conducted to evaluate the seasonal period of dry matter production of irrigatedforages species: Elephantgrass ( Pennisetum purpureum ), Guineagrass cv. Tanzania ( Panicum maximum ),Signalgrass ( Brachiaria decumbens ), Tannergrass ( Brachiaria bryzantha ), Pojucagrass ( Paspalum atratum )and Bermudagrass cv. Coastcross ( Cynodon dactylon ). Climatic conditions and forages cycles were evaluatedduring two years (1999/2000 and 2000/2001). The seasonal production of irrigated pastures is of 65 to 70 days inthe year. In such seasonal period there is no dry matter production even when hydric requirements of grasses aremet through irrigation.Index terms: climatic conditions, forage cycle, forages, dry matter. Introducao No Sudeste do Brasil, os primeiros trabalhos sobreirrigacao de pastagens demonstraram que essa tecnica,apesar de aumentar a producao total de materia secano ano, nao contribuia para alterar a curva deestacionalidade de producao. Guelfi Filho (1972), comirrigacao em capim-elefante, obteve 18,7, 18,4 e 18,2 t ha

Estimativas de ganho genético por diferentes critérios de seleção em genótipos de alfafa

Este estudo foi desenvolvido objetivando comparar diferentes criterios de selecao, indicar o metodo de selecao que propicia maiores estimativas de ganho genetico e identificar genotipos superiores de alfafa quanto a caracteristicas produtivas, morfologicas e bromatologicas. Foram avaliadas a producao de materia seca, altura de planta, tolerância a doencas, aceitacao fenotipica pelos animais, proteina bruta, digestibilidade in vitro da materia seca, fibra em detergente neutro e relacao caule/folha de 92 acessos provenientes do INTA-Argentina, tendo como testemunha o Crioula. Os Indices de Mulamba & Mock, distância do genotipo ao ideotipo e Elston foram os mais adequados a esse tipo de estudo. Os genotipos Sequel, CUF 101, Siriver 2, Florida 77, Diamond, Sequel 2, LE N 2, Medina, Kern, Rio Grande, DK 166, DK 181, Perla SP INTA, WL 516, Rocio, LE Semit 711 e LE N 3 foram os indicados a selecao pelos maiores indices de Mulamba e Mock, distância do genotipo ao ideotipo e indice de Elston.

Manejo de Água de Irrigação para Alfafa (Medicago sativa L.)

This study was conducted to evaluate methods of balancing climatic demand (ECA = class A tank evaporation and PRP = rainfall) with soil conditions (CAD = water storage capacity) of na Hapludox soil, in order to manage supplementary water of alfalfa cultivar Crioula on field conditions. Therefore, the behavior of alfalfa under three soil water conditions (H1 = no irrigation; H2 = efficient water use at plants full vegetative stage when ECA ¾ PRP ³ 30 mm; H3 = full use of water during the entire plant cycle when ECA ¾ PRP ³ 20 mm) were evaluated based on these methods, looking of efficient water use by alfalfa. Results indicated that the technology employed is very efficient in managing supplementary water, in the Hapludox, and that increasing not economic returns with alfalfa, by way of efficient water use (H2 = ECA ¾ PRP >= 30 mm), can be achieved.

Determinação do coeficiente de repetibilidade e estabilização genotípica das características agronômicas avaliadas em genótipos de alfafa no ano de estabelecimento

Repeatibility coefficients were estimated for dry matter production (DMP), plant height at cutting time (PHC), disease tolerance (DT) and height at flowering (HF). The characteristics were evaluated in 92 genotypes in the years 2004 and 2005. Five cuttings were carried out in the rain period (November to March) and six cuttings in the dry period (April to September). The experiment was arranged in randomized block design, with two replications. The estimates of the repeatability coefficient were obtained by different methods and, then, the study of genotype stabilization was performed. The statistical analyses were done using the GENES software. During the dry period, only two cuttings were enough to achieve 85 % accuracy in the estimation of the real DMP value, whereas in the rain period, five cuttings were required to achieve the same reliability. Overall, in the rain period a larger number of evaluations was required to obtain the same data reliability. For genotype stabilization, there was increase in reliability by leaving out some cuttings. The variables DMP and PHC, during the rain period, showed larger estimates for the repeatability coefficient than the variables DT and HF.

Weather, cultivar and density-dependent processes influence on aphid in alfalfa

E importante entender os efeitos do clima, da densidade dos insetos e da cultivar sobre a abundância de insetos para se predizer e prevenir perdas na producao das culturas. O objetivo do presente trabalho foi analisar a influencia desses fatores sobre afideos em alfafa no periodo de um ano. Os dados foram coletados de setembro/1997 a agosto/1998 na Fazenda Canchin (CPPSE-EMBRAPA), Sao Carlos, Sao Paulo, Brasil. As condicoes climaticas, em geral, tiveram pequeno efeito sobre a variacao populacional dos afideos, mas a abundância de Therioaphis maculata esteve negativamente correlacionada a umidade. Alem disso, as altas temperaturas maximas e os baixos niveis de precipitacao pluvial possivelmente favoreceram a alta abundância dessa especie nas cultivares Crioula e P3. Portanto, torna-se importante o manejo desse afideo durante periodos quentes e secos. As variacoes populacionais de Acyrthosiphon spp., T. maculata e Aphis craccivora parecem ser reguladas principalmente por processos dependentes da densidade. Na cultivar resistente CUF 101 observou-se menor abundância de T. maculata e A. craccivora e uma variacao populacional menos pronunciada do que nas demais cultivares, podendo ser utilizada para reducao da populacao dessas especies em campo. Estudos de longa duracao, incluindo os efeitos do clima e da densidade sobre a qualidade da planta, vao contribuir para o manejo de afideos nos alfafais.

Manejo de água para estabelecimento de alfafa (Medicago sativa L.)

The water management for growth of Crioula alfalfa cultivar was evaluated in a field study, in order to assess the effects in the plant establishment up to the first cut, at 1977. The study was carried out in 1997. So that, the behaviour at three growth stages (E1 = early vegetative stage, E2 = full vegetative stage, and E3 = reproductive stage until harvest) in the presence of four water levels (A = 100%, B = 80%, C = 45-50%, and D = 20-25% from a sprinkler irrigation) was studied. Eight combinations were evaluated: 111, 110, 100, 101, 001, 011, 010, 000, where the first digit is E1, the second is E2 and the third is E3. The number 0 in the figures represents the period in which growth stage did not receive water, cover by a mobile structure, which slide on trail, and also protected against occasional rainfall. The number 1 represents the time in which the irrigation water levels were applied. The growth stages of the plants as for dry matter yield, differently respond to the water conditions. The E2 and E3 were the most sensible to water supply and E1 the least sensible; in which the water was detrimental to the plant establishment and yield.