Control by glyphosate and its alternatives of glyphosate‐susceptible and glyphosate‐resistant Echinochloa colona in the fallow phase of crop rotations in subtropical Australia

Echinochloa colona is the most common grass weed of summer fallows in the grain‐cropping systems of the subtropical region of Australia. Glyphosate is the most commonly used herbicide for summer grass control in fallows in this region. The world's first population of glyphosate‐resistant E. colona was confirmed in Australia in 2007 and, since then, >70 populations have been confirmed to be resistant in the subtropical region. The efficacy of alternative herbicides on glyphosate‐susceptible populations was evaluated in three field experiments and on both glyphosate‐susceptible and glyphosate‐resistant populations in two pot experiments. The treatments were knockdown and pre‐emergence herbicides that were applied as a single application (alone or in a mixture) or as part of a sequential application to weeds at different growth stages. Glyphosate at 720 g ai ha^?1 provided good control of small glyphosate‐susceptible plants (pre‐ to early tillering), but was not always effective on larger susceptible plants. Paraquat was effective and the most reliable when applied at 500 g ai ha^?1 on small plants, irrespective of the glyphosate resistance status. The sequential application of glyphosate followed by paraquat provided 96–100% control across all experiments, irrespective of the growth stage, and the addition of metolachlor and metolachlor + atrazine to glyphosate or paraquat significantly reduced subsequent emergence. Herbicide treatments have been identified that provide excellent control of small E. colona plants, irrespective of their glyphosate resistance status. These tactics of knockdown herbicides, sequential applications and pre‐emergence herbicides should be incorporated into an integrated weed management strategy in order to greatly improve E. colona control, reduce seed production by the sprayed survivors and to minimize the risk of the further development of glyphosate resistance.     

Investigating the effectiveness of Mountain Pine Beetle mitigation strategies

We review a broad range of mitigation strategies associated with the management of Mountain Pine Beetle (Dendroctonus ponderosae Hopkins). We consider: methods that are currently utilised or have been proposed for controlling beetle populations; the manner in which the effectiveness of these approaches is monitored and assessed; and the role that remotely sensed data may play in a large-area monitoring system. To this end, we first examine the goals of effectiveness monitoring and introduce a general classification system to clarify the purpose and practice of efficacy monitoring. Based on these principles, the review is then structured around effectiveness evaluations for managing forest pests, primarily Mountain, Southern (Dendroctonus frontalis Zimmermann), and Western Pine Beetles (Dendroctonus brevicomis LeConte) throughout North America, and grouped by management strategy: silvicultural treatments; prescribed burns; and the use of attractants, repellants and insecticides. Finally, we propose the use of remotely sensed data as a complementary tool for monitoring changes in the extent and severity of Mountain Pine Beetle damage across large areas. Use of such data enables assessment of the efficacy of landscape level management practices, directing the application of new mitigation activities, and reducing the risk of future infestations.     

FIELD AND LABORATORY STUDIES COMPARING NUTRISPHERE-NITROGEN UREA WITH UREA IN NORTH DAKOTA,ARKANSAS, AND MISSISSIPPI

Nitrification and ammonia volatility are two important impediments to nitrogen (N) use efficiency and crop uptake around the world. Nutrisphere® is a relatively new product whose manufacturer claims both nitrification and urea volatilization inhibiting properties. Urea coated with Nutrisphere is and the resulting fertilizer is called Nutrisphere®-N urea, or Nutrisphere-N (NSN). Eight field studies on spring (Triticum aestivum L.) or durum [T. turgidum L. subsp duram (Desf.) Husn.] wheat in North Dakota, three field studies in Mississippi/Arkansas on rice (Oryza sativa L.), four laboratory experiments in North Dakota and one in Arkansas were conducted to determine the nitrification and urea volatilization inhibiting ability of NSN compared with urea alone. Results of field and laboratory experiments revealed that the product has no nitrification or urea volatilization inhibiting properties at the recommended rates and spring wheat and rice did not benefit from the application of NSN to urea.     

Effect of cultivar and cadmium rate upon the nutrient content of soybean plants

An experiment was conducted to evaluate the effect of soybean (Glycine max L.) cultivar, Cd rate, and cultivar x Cd rate interaction upon nutrient concentrations in the plant. Cultivars rated as T (tolerant) or S (susceptible) to Cd were included in the study. A factorial combination of 10 cultivars and 4 levels of Cd were randomized in 4 replications of a completely randomized design. Additions of CdCl₂ dissolved in distilled water were made to weighed quantities of dry soil. The soil was a Flanagan silt loam (Aquic Argiudoll). Four weeks after planting, plants were harvested, air dried and dry ashed. Chemical determinations of Zn, Fe, Mn, Cu, K, Ca, Mg and P in plants were made by emission spectroscopy.

Nutrient concentrations were affected by cultivar and rate of Cd and generally, nutrient concentrations decreased as rate of Cd increased. The Cd linear x cultivar interaction significantly affected plant concentration of each element except P indicating that the linear effect of Cd was not consistent among all cultivars. A comparison of “susceptible”; cultivars with “tolerant”; cultivars showed significant differences in nutrient concentration of each element except K. Plant K concentration was significantly associated with a Cd linear x T (tolerant) vs. S (susceptible) interaction indicating that the linear trend due to Cd rate differed between cultivars rated S or T to Cd.     

Peanut seed size and nutritional calcium requirement

A differential response of peanut (Arachis hypogaea L.) cultivars with varying seed sizes to Ca nutrition has been observed for many years. No satisfactory explanation of why different seed sizes respond differently to Ca nutrition was found. Fruit with a wide range of seed sizes were investigated. Fruit characteristics relating to seed size and Ca content expressed as a concentration and as the total amount in a fruit were compared. Ca content expressed as a concentration showed no relationship to seed size. Utilizing total Ca content in a peanut fruit and its volume, it was shown that large‐seeded fruit needed to transport Ca through a longer soil distance to satisfy the fruit's nutritional need than small‐seeded fruit did. This result does not address any Ca nutritional characteristics internal to a peanut fruit nor does it address any genetic nutritional variables.     

Genetic variation for Mg tissue concentration in pearl millet lines grown under Mg stress conditions

Efficient nutrient utilization by plants is extremely important in developing countries and is becoming more important in the developed countries as the costs of fertilizers are increasing. Pearl millet is a world food and forage crop usually grown on droughty soils low in nutrients. Eighty‐five genetically diverse pearl millet, Pennisetum glaucum (L.) R. Br. lines were grown in low Mg and K sand for three weeks to screen for efficient Mg uptake. Magnesium free Hoagland's solution at one‐fourth strength was used to water the plants as needed. Forage produced was clipped, dried, ground, ashed, and analyzed for Mg and K content. A 2‐fold difference for Mg concentration in the forage existed among the lines. The data indicated that a low [K]/[Mg] ratio in the plant was indicative of a Mg efficient genotype. The data also suggest that caution should be used in making general nutrient recommendations based on tissue or soil tests without knowing the nutrient requirement of the cultivar.     

1. An assessment of the ecological basis of game ranching in Southern African savannas

Game and cattle ranching are compared at the three successive levels of primary production, efficiency of vegetation use and secondary production, It appears that the increase in grass growth following bush clearing more than offsets the loss in edible browse, but there is a need for more data. The multiple species utilization theory is considered to have been given an incorrect emphasis. Mixed herbivore communities do make better use of vegetation, but it is the enormous amount of overlap and flexibility in their habitat preferences, movements and diet which is important and which gives the system stability, rather than the earlier concept of non‐overlapping, rather rigid separation. At the secondary production level it is concluded that game are less efficient than cattle for meat production, integrated game and cattle ranching may well be the optimum form of land use and there is a need for a long‐term policy aimed at domestication and selection and breeding programmes using the larger browsing species.     

A gradient analysis of grassed mountain catchments in the natal Drakensberg

Abstract

An indirect gradient analysis was carried out on vegetation and environmental data from the Mdedelelo Wilderness Area of Cathedral Peak State Forest in Highland Sourveld. Vegetation ordination axes were correlated with environmental variables deduced to have influenced species‐composition. Altitude proved a significant conjugate variable in the absence of tractable fire data.     

Intermediate Periodicities in Juniper Consumption and Sampling Strategies to Estimate the Diet of Free-Grazing Goats

We conducted this study to describe the intermediate-term periodicities in percentage juniper (Juniperus spp.) in goat diets and to develop optimal sampling schemes to estimate individual animal variation in juniper consumption. Fecal samples were collected from 12 multiparous female Angora goats on Monday and Thursday for a 24-mo period. Percentage juniper in the diet was determined using fecal near-infrared reflectance spectroscopy. Spectral analysis was used to determine the presence and length of cyclic variation in juniper consumption during growing and dormant season periods. Significant periodicities were found for 37% and 68% of the goats in the dormant and growing seasons, respectively. Cycle lengths varied from 9 d in the dormant season to 7 or 8 d in the growing season. The simple coefficient of determination between a two-sample moving average and the mean of all observations on individual goats was highest during a 3-mo period in the spring, which indicates that samples collected in the spring provided the best estimate of the yearlong percentage juniper in the diet. Monte Carlo simulations for 7-d cycles showed the root mean squared difference between estimated and population mean for two samples with 2 or 3 d between samples was only 1% greater than the root mean square difference for three or four samples collected every other day. The optimal sampling strategy for determining the dietary percentage of a species is to collect two samples separated by one-half of the cycle length.