Giovanni Pruneddu

Tradeoffs between Maize Silage Yield and Nitrate Leaching in a Mediterranean Nitrate- Vulnerable Zone under Current and Projected Climate Scenarios

Future climatic changes may have profound impacts on cropping systems and affect the agronomic and environmental sustainability of current N management practices. The objectives of this work were to i) evaluate the ability of the SALUS crop model to reproduce experimental crop yield and soil nitrate dynamics results under different N fertilizer treatments in a farmer’s field, ii) use the SALUS model to estimate the impacts of different N fertilizer treatments on NO3- leaching under future climate scenarios generated by twenty nine different global circulation models, and iii) identify the management system that best minimizes NO3- leaching and maximizes yield under projected future climate conditions. A field experiment (maize-triticale rotation) was conducted in a nitrate vulnerable zone on the west coast of Sardinia, Italy to evaluate N management strategies that include urea fertilization (NMIN), conventional fertilization with dairy slurry and urea (CONV), and no fertilization (N0). An ensemble of 29 global circulation models (GCM) was used to simulate different climate scenarios for two Representative Circulation Pathways (RCP6.0 and RCP8.5) and evaluate potential nitrate leaching and biomass production in this region over the next 50 years. Data collected from two growing seasons showed that the SALUS model adequately simulated both nitrate leaching and crop yield, with a relative error that ranged between 0.4% and 13%. Nitrate losses under RCP8.5 were lower than under RCP6.0 only for NMIN. Accordingly, levels of plant N uptake, N use efficiency and biomass production were higher under RCP8.5 than RCP6.0. Simulations under both RCP scenarios indicated that the NMIN treatment demonstrated both the highest biomass production and NO3- losses. The newly proposed best management practice (BMP), developed from crop N uptake data, was identified as the optimal N fertilizer management practice since it minimized NO3- leaching and maximized biomass production over the long term.

The response of rate and duration of grain filling to long-term selection for yield in Italian durum wheats.

Genetic advance in durum wheat (Triticum turgidum subsp. durum) grain yield in Italy has been achieved by bringing forward flowering time, achieving a larger number of grains per unit area, and altering the pattern of senescence. The performance, in the absence of any moisture stress, of a set of 6 Italian durum wheat cultivars released over the past 100 years was compared under 4 environments and 2 nitrogen rates, to ascertain whether the changes brought about by selection for yield have also indirectly affected the rate and duration of grain filling. Grain filling lasted 35–36 days in all cultivars except ‘Ichnusa’ (39 days), although modern cultivars flowered earlier than older ones. The lack of any breeding effect on grain-filling duration also meant that the later old cultivars were not negatively affected by the higher ambient temperatures during their grain filling. The maximum rate of grain filling ranged from 2.4 to 3.3 mg/day and showed a highly significant negative correlation with the year of cultivar release (r = –0.91*). The variation in grain weight, significant but not correlated with the year of release, was associated with the rate of grain filling, which was in turn related to the grain number per unit area. A compensating variability still exists among modern Italian cultivars in both grain number and grain-filling rate, which demonstrates that durum wheat grain yield can be increased while also preserving high grain weights.

Effects of triticale cultivars grown in a Mediterranean environment on biomass yield and quality

Riassunto Effetti della scelta varietale sulla produzione di biomassa e sulla qualità di triticale coltivato in ambiente Mediterraneo. Quattro varietà di triticale, Antares, Rigel, Eureka e Magistral, caratterizzate da differente habitus (invernale vs. primaverile) sono state coltivate a due densità di semina (350 vs. 700 semi/m2) per due anni. Le piante sono state quindi campionate allo stadio di fioritura e di maturazione latteo-cerosa. La densità di semina non ha influenzato la produzione di biomassa e la composizione chimica. Le varietà ad habitus primaverile hanno avuto, in entrambe le annate, una migliore composizione chimica di quelle invernali, mentre non ci sono state differenze per la produzione di biomassa. Fra le due epoche di raccolta quella più anticipata (fioritura) è risultata meno condizionata dall’andamento meteorologico ed ha consentito di ottenere erbe con concentrazione di SS ottimale per la produzione di insilati.