Water use efficiency and shoot biomass production under water limitation is negatively correlated to the discrimination against 13C in the C3 grasses Dactylis glomerata, Festuca arundinacea and Phalaris arundinacea.

Climate change impacts rainfall patterns which may lead to drought stress in rain-fed agricultural systems. Crops with higher drought tolerance are required on marginal land with low precipitation or on soils with low water retention used for biomass production. It is essential to obtain plant breeding tools, which can identify genotypes with improved drought tolerance and water use efficiency (WUE). In C3 plant species, the variation in discrimination against 13C (Δ13C) during photosynthesis has been shown to be a potential indicator for WUE, where discrimination against 13C and WUE were negatively correlated. The aim of this study was to determine the variation in the discrimination against 13C between species and cultivars of three perennial C3 grasses (Dactylis glomerata (cocksfoot), Festuca arundinacea (tall fescue) and Phalaris arundinacea (reed canary grass)) and test the relationships between discrimination against 13C, season-long water use WUEB, shoot and root biomass production in plants grown under well-watered and water-limited conditions. The grasses were grown in the greenhouse and exposed to two irrigation regimes, which corresponded to 25% and 60% water holding capacity, respectively. We found negative relationships between discrimination against 13C and WUEB and between discrimination against 13C and shoot biomass production, under both the well-watered and water-limited growth conditions (p < 0.001). Discrimination against 13C decreased in response to water limitation (p < 0.001). We found interspecific differences in the discrimination against 13C, WUEB, and shoot biomass production, where the cocksfoot cultivars showed lowest and the reed canary grass cultivars highest values of discrimination against 13C. Cocksfoot cultivars also showed highest WUEB, shoot biomass production and potential tolerance to water limitation. We conclude that discrimination against 13C appears to be a useful indicator, when selecting C3 grass crops for biomass production under drought conditions.

Power plant intake quantification of wheat straw composition for 2nd generation bioethanol optimization--a Near Infrared Spectroscopy (NIRS) feasibility study.

Optimization of 2nd generation bioethanol production from wheat straw requires comprehensive knowledge of plant intake feedstock composition. Near Infrared Spectroscopy is evaluated as a potential method for instantaneous quantification of the salient fermentation wheat straw components: cellulose (glucan), hemicelluloses (xylan, arabinan), and lignin. Aiming at chemometric multivariate calibration, 44 pre-selected samples were subjected to spectroscopy and reference analysis. For glucan and xylan prediction accuracies (slope: 0.89, 0.94) and precisions (r(2): 0.87) were obtained, corresponding to error of prediction levels at 8-9%. Models for arabinan and lignin were marginally less good, and especially for lignin a further expansion of the feasibility dataset was deemed necessary. The results are related to significant influences from sub-sampling/mass reduction errors in the laboratory regimen. A relative high proportion of outliers excluded from the present models (10-20%) may indicate that comminution sample preparation is most likely always needed. Different solutions to these issues are suggested.

Leaching in Small Lysimeters of Nitrate Derived from Nitrogen-15-Labeled Field Pea Residues.

Field pea (Pisum sativum L.) crop residues labeled with 15 N were incorporated during September in small monolith lysimeters of a sandy loam soil. The leaching of 15 N-labeled and nonlabeled NO3 to below 45 cm was studied during the subsequent 2 to 3 yr comparing (i) planted vs. unplanted soil and (ii) with and without pea residue incorporation. The peak flux of labeled NO3 -N from uncropped soil occurred in December. During the first leaching period (September-April), 15 and 7% of the residue N was recovered as NO3 in the percolate in the two experiments, corresponding to 18 and 13% of total NO3 -N in the percolates, respectively. The difference observed in leaching of labeled N in the two experiments was mainly due to a much higher drainage volume in the first experiment. The different residue particle sizes, 10 mm or <3 mm, used in the two experiments may have influenced the immobilization-mineralization of N in the soil differently and consequently the potential for NO3 leaching. Pea residue N constituted 10 to 15% and 5% of total NO3 -N leached from unplanted soil in the second and third leaching periods, respectively. Incorporating the ground pea residues reduced the total amount of NO3 leached by 15% during the first leaching period, indicating that the pea residue may be an important factor in controlling leaching losses. Ryegrass (Lolium perenne L.) established on lysimeters at the time of residue incorporation reduced the total leaching of N in the first leaching period by 15%, but in the second and third leaching period grass eliminated NO3 leaching completely.