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Irrigated winter crops can reduce input demands when compared with irrigated summer cropping systems in the Mediterranean area. The sustainability of these systems can be further improved resorting to diverse rotations, but also to fertilisation with digestate, a by-product from anaerobic digestion of organic waste. Post-treatments such as drying and acidifying can improve the fertiliser value of this product. In this study, we compare wheat performance in a three-year full cereal rotation or in a diverse rotation, with pea and canola. Besides, untreated and dried acidified digestates are tested as fertilisers for all crops, comparing to mineral fertilisation at a rate of 140 kg N ha−1 and a control with no fertilisation. To assess productivity and efficiency of the different systems, grain yield and N concentration, N uptake efficiency (NUpE) and water use efficiency (WUE) were determined, along with soil nitrate dynamics and total N at the end of the experiment. Results showed an average wheat yield increase of 1.79 t ha−1 by the last year of the diverse crop rotation rather than the cereal rotation (p < 0.001). Although there was no yield increase in the previous year, wheat after pea showed higher grain N concentration (p < 0.001). However, the NUpE of wheat remained steady due to a higher soil N availability after pea, which suggests that fertilisation can be adjusted. Although wheat WUE increased due to canola and pea precedents (p < 0.001), the cereal rotations should be more adapted to systems with low water availability. Nonetheless, both rotations required about 30% of irrigated water than the typical irrigated summer crops of the Ebro valley region. Fertiliser effect on yields was variable according to the tested crop mainly due to differences in N demand along each growing cycle. Overall, dried acidified digestate application resulted in similar soil nitrate levels than the mineral fertiliser. The diverse rotation raised soil nitrates content compared to the cereal rotation at sowing and harvesting times (p = 0.002 and p < 0.001, respectively). Higher soil nitrate levels were found when associating these two practices, while nitrate levels after mineral fertilisation showed to be less dependent on the implemented rotation. The diverse rotation also raised soil total N at the end of the experiment (p = 0.023). Similarly, the dried acidified digestate application resulted in higher soil total N than mineral fertilisation (p = 0.011). These findings show how these management practices should allow for a chemical fertilisation reduction in irrigated winter crop systems. [Display omitted] • The use of a diverse crop rotation and dried acidified digestate reduce chemical fertiliser needs. • Preceding wheat with canola and pea increases yields and N in grain. • Water use efficiency of wheat is higher in a diverse rotation. • Digestate suitability for fertilisation depends on the crop. [ABSTRACT FROM AUTHOR]

Selection criteria for drought tolerance would be helpful tools for wheat breeding programmes. To assess the usefulness of some morphological traits above the flag leaf node as indicators of yield and the susceptibility index (SI) of Fischer and Maurer, 10 durum wheat genotypes were used in experiments conducted under two water regimes at two latitudes in Spain during 3 years. Morphological traits were measured at anthesis, and yield, yield components and quality traits were evaluated at ripening. Principal components analysis showed associations between morphological traits and yield, yield components and quality, most of them caused by differences between environments. Peduncle weight, spike weight and length and awn length were significantly related to SI within environments. Spike and peduncle weight were the traits more related to yield and SI in all the experiments together and in the rainfed sites, while in the irrigated sites spike length was better. The spike weight and length were negatively associated with SI, while peduncle weight was positively associated to SI. Genotype means across all experiments were associated with SI values. These morphological traits could be selection criteria in breeding programmes to obtain varieties with good yield stability. The genetic variability found suggests opportunity for selection. [ABSTRACT FROM AUTHOR]

The ability to assess green biomass is of particular interest in a number of wheat breeding environments. However, the measurement of this and similar traits is either tedious and time-consuming or requires the use of expensive, sophisticated equipment, such as field-based spectroradiometers to measure vegetation indices (VIs). Here, conventional digital cameras are proposed as affordable and easy-to-use tools for gathering field data in wheat breeding programmes. Using appropriate software, a large set of images can be automatically processed to calculate a number of VIs, based on the performance of simple colour operations on each picture. The purpose of this study was to identify a set of picture-derived vegetation indices (picVIs) and to evaluate their performance in durum wheat trials growing under rainfed and supplementary irrigation conditions. Here, zenithal pictures of each plot were obtained roughly 2 weeks after anthesis, and the picVIs that were calculated were compared with the normalised difference vegetation index (NDVI), an index derived from spectroradiometrical measurements, and with the grain yield (GY) from the same plots. The picVIs that performed best were the Hue, CIE-Lab a* and CIE-Luv u* components of the average colour of each picture, the relative green area (GA) and the ‘greener area’, similar to GA but excluding the more yellowish-green pixels. Our results showed a high correlation between all these picVIs and the NDVI. Moreover, in rainfed conditions, each picVI provided an estimation of GY similar to or slightly better than that provided by the NDVI. However, in irrigated conditions during anthesis, neither these picVIs nor the NDVI provided a good estimation of GY, apparently because of the saturation of the VI response in conditions of complete soil cover and high plant density. [ABSTRACT FROM AUTHOR]

Abstract: The estimation of grain yield before harvesting could be a very useful tool for breeding programs and productivity forecasting. Canopy reflectance indices have been used for yield estimation, but with limited success. This work was carried out to study the suitability of the visible and near-infrared reflectance spectrum of the canopy for the assessment of grain yield in a set of durum wheat genotypes. Five field experiments, each one including 25 genotypes, were conducted in low, medium and high productivity environments, with average yields of 2.5, 4.5 and 7t/ha. Spectral reflectance measurements between 400 and 1000nm were made at anthesis and milk-grain stages. Partial least squares regression (PLSR) was used in the construction of models that were tested by simple regression between genotype means of predicted and observed grain yields. The empirical models for the estimation of grain yield showed generally stronger and more robust assessment of grain yield than previously assayed spectral indices. For the best model, correlation coefficients between genotype means of predicted and measured yield within each of the five environments ranged from 0.53 to 0.76. We concluded that, although the models did not provide an accurate quantification of grain yield, they could still be used to rank genotypes for breeding purposes. The most reliable ranking of genotypes was attained using measurements made at milk-grain stage on medium to high productivity environments. [Copyright &y& Elsevier]

Future wheat yield improvements may be gained by increasing total dry matter (TDM) production. Vegetation indices (VI) based on spectral reflectance ratios have been proposed as an appropriate method to assess TDM and leaf area index (LAI) in wheat. This study was undertaken to determine whether VI could accurately identify TDM and LAI in durum wheat (Triticum turgidum var. durum (Desf.) Bowden [= T. turgidum subsp, durum (Desf.) Hush.]} and serve as indirect selection criteria in breeding programs. Total dry matter and LAI were determined from destructive sampling from booting to milk-grain in seven field experiments conducted under Mediterranean conditions. Each experiment included one of two sets of 20 or 25 genotypes. Field reflectance values were collected using a portable field spectroradiometer. Two VI, the normalized difference vegetation index (NDVI) and the simple ratio (SR), were derived from spectral measurements and their predictive value for TDM and LAI was evaluated. The best stages for growth trait appraisal were Stages 65 and 75 of the Zadoks scale. The power of VI for assessing TDM was lower than their predictive value for LAI. The suitability of VI for the assessment of growth traits depended on the range of variability existing within the experimental data. Vegetation indices accurately tracked changes in LAI when data were analyzed across a broad range of different growth stages, environments, and genotypes. However, their value as indirect genotypic selection criteria for TDM or LAI was limited, since they lacked predictive ability for specific environment/ growth stage combinations. [ABSTRACT FROM AUTHOR]

Future increases in the potential yield of wheat will require an improvement in the photosynthetic area in early growth stages. Our aim was to investigate the genotypic and environmental effects on the pattern of leaf and green area development of durum wheat (Triticum turgidum L. cv. durum). Twenty-five genotypes were grown during 2 years under irrigated and rainfed conditions in Lleida (northeastern Spain). Leaf area index (LAI) and green area index (GAI) were determined on eight occasions from seedling to maturity and data were fitted to an asymmetric logistic peak curve. Multivariate analysis of variance was used to assess the curve characteristics responsible for differences between years, sites and genotypes. Genotypic differences in the pattern of changes in LAI and GAI from sowing to maturity were not statistically significant, indicating a lack of genetic diversity for these traits in the germplasm used in this study. A decrease in the peak of the curves of 27% for LAI and 35% for GAI was observed under rainfed conditions compared to the irrigated site. Drought caused a lengthening of crop development until anthesis of about 2% (3–4 days). Contrarily, the time from sowing to the maximum LAI and GAI values were reduced by drought in around 10%, causing an acceleration of the onset of plant senescence. Once started, the senescence of the green organs of the plant was more rapid at the irrigated than at the rainfed site. It is concluded that LAI and GAI patterns were more influenced by the environment (mainly water availability) than by the genotype. The results suggest a certain degree of independent regulation for phenological development and the swiftness of green area accumulation in the plant. [Copyright &y& Elsevier]