Research Progress Report, No. 4

The fertilizer application method used for producing small grains in interior Alaska is not always a matter of choice but of necessity. Farmers must fertilize, till, and seed a large acreage in a short time to complete the seeding operation no later than the last week in May. In most years, this allows time for the crop to mature before being damaged by autumn frosts. A typical fertilizer application for barley is 380 pounds per acre dry, blended material consisting of 100 pounds urea as the primary nitrogen (N) source, 100 pounds monoammonium phosphate, 100 pounds ammonium sulfate, and 80 pounds potassium chloride. This combination provides an application ratio of 77-51-48-24 pounds per acre N, P20 5, K20 , and sulfur (S). This means a farmer planting 1000 acres of barley must handle 190 tons of fertilizer material. The most expedient method is to use a 10- to 20-ton capacity, trailer-type, broadcast spreader which minimizes refilling time. If fields are tilled after fertilization, the material is mixed into the soil; otherwise the fertilizer remains on the soil surface. There are several reasons to investigate other methods of fertilizer application even though this system has worked reasonably well. Most barley produced in interior Alaska is seeded on lands which have been cleared of native vegetation in the last ten years (Lewis and Thomas 1982). Soils are naturally infertile and are cool throughout the growing season (Siddoway et al. 1984), and most have been cropped for only three or four years. Delucchi (1983) reported higher yield response when phosphorus (P) was banded with the seed than when equal applications were broadcast. This is not atypical for P-deficient soils (Cooke 1982). Some farmers in Alaska’s interior have begun to band a starter or “ pop-up” fertilizer in the row with the seed at the time of planting. Monoammonium phosphate (11 pounds N and 51 pounds P20 5 per acre) is typically used. Starter fertilizers banded with the seed render nutrients readily available to the seedlings and may boost plant growth early in the season helping seedlings overcome stress due to cold soil temperatures at planting and during early growth (Veseth 1986, Paul 1987). Yields could potentially be increased and/or fertilizer requirements reduced. A general rule has been to band no more than 140 pounds per acre total fertilizer containing no more than 15 to 20 pounds N per acre with the seed (Loynachan et al. 1979). Particular caution is urged when urea is used as an N source (Cooke 1982, Robertson 1982). There is a possibility of seedling injury from excessive salts or the release of toxic quantities of ammonia near the seed. Several farmers in the interior of Alaska have banded the total nutrient requirement for barley with the seed using urea as the major N source. Good yield results have been reported for several years with no evidence of crop injury at rates of up to 450 pounds of total material per acre. Delucchi (1983) speculated that in wetter soils, typical of newly cleared lands, salts may tend to dissolve and diffuse away from the seed thereby lessening the potential for seedling damage. Banding the full nutrient requirement for barley with the seed may increase yields over those found when the equal amount is broadcast, thus increasing returns. Elimination of the broadcast operation will reduce costs slightly. Urea is available locally at a lesser cost than other N sources which must be shipped into the state and may be more cost effective than other formulations

Evaluating the influence of wetland vegetation on chemical residence time in Mississippi Delta drainage ditches

The presence of emergent vegetation within channelized aquatic environments has the capacity to provide a number of biological functions as well as alter the hydrology of the system. Vegetation within the channel exerts roughness, drag and friction on flowing water, reducing flow rates, increasing water depths and increasing hydraulic retention time. By increasing the hydraulic retention time, chemical residence time (CRT) is increased, thus improving the potential of pollutant mitigation. The study compared two geomorphologically similar drainage ditches, one vegetated and one non-vegetated to evaluate the effect obligate, in-stream wetland vegetation had on CRT. A fluoride (F-) tracer was amended to both ditches with nutrients and sediments to simulate stormwater runoff event. The measured CRT of the vegetated drainage ditch was at least twice that of the non-vegetated ditch. These results suggest that with the presence of vegetation increasing CRT, chemical removal rates will improve, and as a result increase the possibility of microbial transformation, adsorption, and macrophyte assimilation. By dredging or clear-scraping ditches and removing the vegetative component, farmers and managers alike will increase water flows, decrease CRT and potentially increase pollutant loads into aquatic receiving systems.Drainage ditch Residence time Aquatic system

Long-term tillage and crop sequence effects on wheat grain yield and quality.

Much research around the world has compared the performance of cereals grown under conventional and conservation tillage systems; however, relatively few long-term experiments have been conducted in Mediterranean areas, and little attention has been given to interactions among tillage techniques and other system components across space and time. In this study, we investigated the effects of the long-term (18-yr) use of three tillage techniques (conventional tillage, CT; reduced tillage, RT; and no-till, NT) on wheat (Triticum durum Desf.) grain yield and quality within three crop sequences: continuous wheat, faba bean (Vicia faba L.)\u2013wheat, and berseem clover (Trifolium alexandrinum L.)\u2013wheat. In addition, we investigated the effects of climatic variability on the treatments and evaluated whether cumulative effects occurred from continuous treatment. On average, NT resulted in a grain yield advantage over CT when water stress was high and, conversely, a disadvantage when water stress was low. The effect of the tillage system on grain yield varied by crop sequence. Grain yield differences between NT and CT when wheat was grown after faba bean or berseem clover were explained primarily by climatic variability without a cumulative effect over time. In contrast, in continuous wheat, NT resulted in a progressive decrease in grain yield compared with CT. On average, wheat grain protein content varied significantly by tillage system (CT > RT > NT). This suggests that fertilizer N requirements increase with NT compared with CT because of changes in N cycling that lead to a reduction in plant-available soil N

Relating endocrinology, physiology and behaviour using species with alternative mating strategies

1. Recent reviews demonstrate that genetically determined alternative mating strategies (AMS) are widespread and typically consist of morphs that are recognized by morphological or colour traits. Despite well-established behavioural differences associated with each morph, and evidence that androgens are involved in the induction of morphs, few studies have examined whether morphs also vary in whole-organismal performance traits, which may affect dominance status, resource holding potential (RHP) or mate attraction. 2. Our survey revealed a link between androgens and physiological performance traits that are associated with territorial or courtship displays across vertebrate taxa, although the number of species in the sample is limited. Experimental elevation of testosterone alters muscular contractile properties, swimming performance, sprint speed and endurance in males. Whether morphs differ in physiological capacities is relatively unexplored, although recent studies have found that males with high dominance status also exhibit greater physiological capacities (locomotor performance, call duration). 3. Multiple studies support the hypothesis that elevated testosterone results in fitness trade-offs. Potential costs of testosterone include impaired immune function, higher parasite loads, greater energetic requirements and ultimately reduced survival. Long term studies of Uta stansburiana highlight the trade-offs among life-history traits induced by variation in testosterone. Circumstantial evidence suggests a role of testosterone in depressing immune function in species with AMS. 4. We argue that hypotheses regarding the role of trade-offs in shaping selection on functional modules, which are involved in sexual selection, are best developed by manipulative studies on discrete morphs. Our review highlights the need to measure multiple traits to provide additional insights into the roles of sexual selection and physiological epistasis in maintaining intraspecific variation in reproductive phenotypes. The integration of endocrine control of behaviour, physiology and performance is rarely attempted in most studies and may be facilitated by analyses that focus on estimating correlational selection