Response of corn to combinations of atrazine, propyl gallate and ozone

Growth chamber experiments were conducted to determine the influence of the air pollutant ozone (O₃) [0.2 and 0.3 ppm (v/v)] on the growth of corn (Zea mays L.) treated with the herbicide atrazine (2.5 and 3.5 kg/ha) and the antioxidant propyl gallate (5 and 8 kg/ha). At both concentrations O₃ at 0.3 ppm alone reduced dry weights of corn and chlorophyll. Chlorophyll a was more affected than chlorophyll b by O₃ at 0.3 ppm alone and in combination with atrazine. Propyl gallate at both rates protected corn against O₃ injury. The interaction between atrazine and O₃ at 0.2 ppm was additive whereas at 0.3 ppm it was antagonistic. But combinations of atrazine and propyl gallate did not protect corn from O₃ injury.     

Nutrient and Microbial Dynamics in Biosolids Amended Soils Following Rainfall Simulation

Municipal waste treatment plants are mandated by U.S. EPA to treat domestic wastewater prior to releasing it to receiving streams. The dewatering and high temperature drying processes at the plant are considered effective in reducing microbial contaminants in the waste. The resulting solid material (biosolid) is rich in nutrients that may serve as a value-added product for plant growth. In this study, we examined the nutrient value of biosolids, their potential biological and chemical risks that could result from surface application to two Mid-Atlantic soils: Bojac (coarse-loamy, mixed, thermic Typic Hapludult) and Cullen (clayey, mixed, thermic Typic Hapludult). Soils were placed on tilt beds and packed to their respective bulk density. Biosolids were added at a rate of 2.24 Mg/ha equivalent and mixed with the top 5 cm of the soil bed. Simulated rain was applied at a rate of 65 mm h^?1 for 45 minutes. Surface runoff and percolation water were collected and analyzed for elemental content, Escherichia coli (E. coli) and total coliform bacteria. Among the nutrient elements of concern (P, Zn, Mn, and Cu) in biosolids, none were found to be higher than the specified EPA limits. The concentration of P was highest in runoff and percolation water from beds packed with Bojac and biosolids. The combined effects of high clay (35%), Al (1.14%), and Fe (5.11%) in Cullen increased its P-adsorbing capacity. Low levels of E. coli and other coliform bacteria were present in samples from biosolids-treated beds packed with Cullen. Microbial counts in runoff and percolation samples varied with soil type; in some instances they were ten-fold higher in Bojac than in Cullen. The results obtained in this study suggest that surface runoff from land applications of biosolids might contribute to microbial contamination of receiving waters near agricultural fields.     

Host range evaluation of the leaf-feeding beetle,Zygogramma bicolorata and the stem-boring weevil,Listronotus setosipennis demonstrates their suitability for biological control of the invasive weed,Parthenium hysterophorus in Ethiopia

The invasive weed, parthenium (Parthenium hysterophorus L.) (Asteraceae: tribe Heliantheae), damages agriculture, adversely impacts biodiversity and is hazardous to human and animal health in Ethiopia. The host range of two natural enemies, a leaf-feeding beetle, Zygogramma bicolorata (Coleoptera: Chrysomelidae) and a stem-boring weevil, Listronotus setosipennis (Coleoptera: Curculionidae) was evaluated for biological control of the weed in Ethiopia. The specificity of Z. bicolorata and L. setosipennis was assessed against 29 and 31 non-target plant species, respectively. The host range of Z. bicolorata and L. setosipennis was first assessed using no-choice tests to examine their oviposition and feeding response on non-target plants. Although oviposition by Z. bicolorata occurred on six non-target species in four Asteraceae species in no-choice tests, it was significantly lower than on parthenium and no larvae developed. Zygogramma bicolorata nibbled the leaves of one of the five niger seed (Guizotia abyssinica L. – an oil seed crop closely related to parthenium) cultivars tested, but feeding and oviposition were significantly less than on parthenium. Furthermore, choice tests indicated that Z. bicolorata did not oviposit nor feed on G. abyssinica when parthenium was present. In no-choice tests, L. setosipennis did not oviposit on any of the non-target species assessed. Mean oviposition on parthenium was 39.0?±?3.4 eggs per plant whereas no eggs were laid on any of the 31 species tested. Based on these and other host range tests, permission was obtained to field release Z. bicolorata and L. setosipennis in Ethiopia.     

Allelopathic effect of lantana on some agronomic crops and weeds

Summary The allelopathic effects of dried lantana shoot residues was examined on wheat, corn, soybean, Virginia pepperweed and velvetleaf on growth over a 30-day period. Significant differences in the growth of the test species were observed. Corn was the most sensitive and wheat was least affected by lantana residues. The other three species were intermediate in their growth response to lantana. Shoot lengths were affected in corn and velvetleaf while root length was reduced in all species except wheat. The shoot dry weights of wheat and soybean were not reduced by lantana residues. In the other three species there was a significant reduction of shoot dry weight due to lantana. The root dry weights of all the five species were reduced by lantana residue. The results demonstrated an overall rate dependent response of the plant species to lantana shoot residue concentrations. Florida Agricultural Experiment Station Journal Series No. 7166. Research Associate and Associate Professor, respectively.