Do Aqueous Extracts from Buckwheat Compromise Seed Germination and Initial Development of Bidens pilosa and Euphorbia heterophylla?

Fagopyrum esculentum Moench (buckwheat) is a dicot species from the Polygonaceae family used as a cover crop in agricultural systems featured with a remarkable allelopathic potential for weed control, helping herbicide-resistance management and promoting substantial reductions in herbicide applications. The aim of this research was to examine the allelopathic potential of aqueous extracts from seeds and aerial part of buckwheat on seed germination and initial development of Bidens pilosa and Euphorbia heterophylla. Bioassay experiments were conducted under a completely randomized experimental design with four replications, containing 50 seeds each. Both weed seed species were harvested in a soybean field, and seed viability was previously assessed. Seeds were exposed to four concentrations (0, 25, 50, and 100%) from extracts of seeds (ES) and aerial part (EAP) of buckwheat. Germination speed index (GSI) in B. pilosa and E. heterophylla was daily evaluated throughout 14 and 16 days, respectively, whereas percentage of germination, abnormal seedlings, as well as non-germinated seeds, root (RL) and aerial part length (APL), and total dry matter (TDM) were rated at final germination test. EAP reduced the GSI, especially under the 100% concentration. Germination percentage was lower and abnormal seedlings increased for both weed species when seeds were exposed to EAP concentrations greater than 25%. However, ES did not impinge upon E. heterophylla germination. EAP and ES reduced the APL, RL, and TDM for concentrations greater than 50%, except for ES which did not affect E. heterophylla development. Both extracts from buckwheat have a high capacity to inhibit germination and compromise seedling development, culminating in such a potential alternative for B. pilosa and E. heterophylla management in agricultural systems.

Impact of Fungicide Spray Timings on Foliar Diseases Control in Wheat Cultivars

Wheat (Triticum aestivum L.) is grown throughout the winter time in Southern Brazil and turns out to be the main agricultural crop at such a year season in the State of Paraná. However, throughout the crop growing season foliar diseases significantly compromise commercial yields in such a manner as to justify the application of fungicides at the right time to control foliar diseases in production fields. The aim of the current manuscript was to assess the impact of different timings for fungicide application (epoxiconazole + pyraclostrobin) on the control of leaf rust (Puccinia triticina E.) and yellow spot (Pyrenophora tritici-repentis) diseases in two wheat genotypes featured by distinct levels of susceptibility in Southern Brazil. A field trial was conducted in Ponta Grossa, State of Paraná, Brazil, in light of split plot statistical design at an experimental area belonging to CESCAGE. The following treatments were imposed in the current study: control (with no sprays);sprays at the first node, booting and heading;sprays at stem extension and flowering;sprays at booting and heading. Throughout the entire crop growing season, the control treatment was conducive to the highest severity levels for both diseases. The increasing of the area under the diseases progress curve assessed herein substantially impinged upon yield components of both wheat genotypes under scrutiny. In general, fungicide sprays at the first node did not culminate in economical advantages. The best timing for fungicide application was the one ascribed to booting and heading stages.

Effects of Climate and Agricultural Practices on Temporal Progress of Sclerotinia sclerotiorum for Soybean in Brazil

Currently the soybean crop is affected by the white mold (Sclerotinia sclerotiorum). The disease can reduce the crop yield and quality and decrease the prices of agricultural lands. The aim of the current research was to assess epidemiology of white mold on soybean crop grown at Arapoti, PR, Brazil, utilizing data related to agricultural practices and local meteorological factors. The experiment was conducted in a naturally infested area. The soybean crop was sown on October 18th, 2011. The experimental design adopted herein was a randomized block in a factorial combination with 4 row spacings (0.35, 0.45, 0.60, 0.75 m) and 4 plant populations (150, 200, 250, 300 thousand plants per hectare) and 4 replications. The temporal analysis of the epidemic was evaluated using mathematical models, such as Logistics, Monomolecular and Gompertz, in order to determine the best model that described the progress of the disease as a function of local meteorological elements. For the incidence data it has been shown that both logistic and monomolecular models were those that were best fitted to the experimental data. For severity, the best model related to the experimental data was the logistic one. Either for incidence or for severity, air temperature was considered to be the environmental factor most affecting the progress of the disease. The variability in the apparent infection rates of white mold on soybean was not affected by different row spacings and plant populations;therefore, suggesting that macroclimatic variations prevailed in such a fashion to mitigate the effect of cultural practices adopted in the field.

Agrometeorological and Soil Criteria for Defining Workable Days for Rational Mechanized Sugarcane Harvest in Southern Brazil

The number workable days (NWD) for agricultural field operations is of great importance for sizing agricultural machinery fleets. This is especially pivotal for sugarcane harvest, which extends from 8 to 10 months/year. In light of this, the current study aimed at defining criteria for obtaining the NWD for rational sugarcane harvest at different sites in the state of São Paulo, southern Brazil, taking into account both a general and a specific criteria. For this purpose, data from harvest interruption of 30 sugar mills in southern Brazil throughout periods ranging from two to five years were used. The following variables were tested as criteria for defining harvest interruption: minimum precipitation (PREC);soil water holding capacity (SWHC);and the limit of the ratio between actual soil moisture (SM) and SWHC. Based on such a specific criterion ascribed to each site along with a general criterion, NWD maps were prepared for the state of São Paulo, Brazil. The results showed that there were variations from the definition criteria of NWD at the different sites in the state. However, the use of a general criterion for harvest interruption, based on PREC ≥ 3 mm, SWHC = 40 mm and SM/SWHC ≥ 90%, provided accurate results. During the validation of these criteria, the NWD maps generated from the individual criterion proposed for each site resulted in an average error of 24.9 days/year, whereas the map generated from the general criterion culminated in an average error of 4.4 days/year.