Nitrogen Use in Durum and Selected Brassicaceae Oilseeds in Two-Year Rotations

Brassicaceae oilseeds can serve as potential feedstocks for renewable biofuels to offset demand for petroleum-based alternatives. However, little is known about oilseed crop yield potential and N use in semiarid, wheat (Triticum spp.)-based cropping systems that dominate the northern Great Plains (NGP). A 5-yr study was conducted in northeast Montana to investigate the yield potential of a direct seeded system of durum (T. durumDesf.) in rotation with either chemical fallow or three Brassicaceae oilseeds: camelina [Camelina sativa (L.) Crantz], crambe (Crambe abyssinica Hochst. ex R.E. Fries), and canola-quality Brassica juncea L. Overall, results from the study indicated that seed yield in the three Brassicaceae oilseeds tested in rotation with durum was related (P \u3c 0.001; r2 = 0.68) to a nitrogen recovery index (NRI), indicating the importance of nitrogen use (NU) efficiency in dryland oilseed production, and that B. juncea generally used N more efficiently than crambe and camelina. Similarly, NRI was related (P \u3c 0.001; r2 = 0.72) to grain yield in durum following oilseeds. Grain yield of durum following B. juncea was similar to durum following fallow and greater than durum following camelina or crambe. Durum following crambe tended to use N more inefficiently than durum following camelina, B. juncea, or fallow. Differences in yield and N use of durum and oilseeds varied among years, which underscores the need to further develop management tools to optimize durum-oilseed cropping systems in highly variable rainfall environments typical of the NGP

Morphological and Geochemical Evidence of Eumelanin Preservation in the Feathers of the Early Cretaceous Bird, Gansus yumenensis

Recent studies have shown evidence for the preservation of colour in fossilized soft tissues by imaging melanosomes, melanin pigment containing organelles. This study combines geochemical analyses with morphological observations to investigate the preservation of melanosomes and melanin within feathers of the Early Cretaceous bird, Gansus yumenensis. Scanning electron microscopy reveals structures concordant with those previously identified as eumelanosomes within visually dark areas of the feathers but not in lighter areas or sedimentary matrices. Fourier transform infrared analyses show different spectra for the feathers and their matrices; melanic functional groups appear in the feather including carboxylic acid and ketone groups that are not seen in the matrix. When mapped, the carboxylic acid group absorption faithfully replicates the visually dark areas of the feathers. Electron Paramagnetic Resonance spectroscopy of one specimen demonstrates the presence of organic signals but proved too insensitive to resolve melanin. Pyrolysis gas chromatography mass spectrometry shows a similar distribution of aliphatic material within both feathers that are different from those of their respective matrices. In combination, these techniques strongly suggest that not only do the feathers contain endogenous organic material, but that both geochemical and morphological evidence supports the preservation of original eumelanic pigment residue

SOIL QUALITY IN RELATION TO FOREST CONVERSION TO PERENNIAL OR ANNUAL CROPPING IN SOUTHERN BRAZIL

Many forested areas have been converted to intensive agricultural use to satisfy food, fiber, and forage production for a growing world population. There is great interest in evaluating forest conversion to cultivated land because this conversion adversely affects several soil properties. We examined soil microbial, physical, and chemical properties in an Oxisol (Latossolo Vermelho distrófico) of southern Brazil 24 years after forest conversion to a perennial crop with coffee or annual grain crops (maize and soybeans) in conventional tillage or no-tillage. One goal was to determine which soil quality parameters seemed most sensitive to change. A second goal was to test the hypothesis that no-tillage optimized preservation of soil quality indicators in annual cropping systems on converted land. Land use significantly affected microbial biomass and its activity, C and N mineralization, and aggregate stability by depth. Cultivated sites had lower microbial biomass and mineralizable C and N than a forest used as control. The forest and no-tillage sites had higher microbial biomass and mineralizable C and N than the conventional tillage site, and the metabolic quotient was 65 and 43 % lower, respectively. Multivariate analysis of soil microbial properties showed a clear separation among treatments, displaying a gradient from conventional tillage to forest. Although the soil at the coffee site was less disturbed and had a high organic C content, the microbial activity was low, probably due to greater soil acidity and Al toxicity. Under annual cropping, microbial activity in no-tillage was double that of the conventional tillage management. The greater microbial activity in forest and no-tillage sites may be attributed, at least partially, to lower soil disturbance. Reducing soil disturbance is important for soil C sequestration and microbial activity, although control of soil pH and Al toxicity are also essential to maintain the soil microbial activity high