Lolium perenne L. (perennial ryegrass) is the most important pasture grass species in temperate regions of the world. However, its growth is restricted in summer dry environments. Germplasm screening ...can be used to identify accessions or individual plants for incorporation into breeding programs for drought tolerance. We selected nine perennial ryegrass accessions from different global origins and from a range of climatic and environmental conditions. In addition, the perennial ryegrass cultivar 'Grasslands Impact' was chosen as a reference. The accessions were grown for 360 days in a controlled environment through six consecutive drought stress and recovery cycles. We observed intraspecific differences in drought stress responsiveness for shoot biomass and survival from the third stress cycle. An accession from Norway had 50% more shoot dry matter than the next best-performing accession after six drought cycles. Compared with the reference cultivar 'Grasslands Impact', shoot dry matter of the accession from Norway was more than seven times higher after six drought cycles, indicating superior performance of this ecotype under drought stress. Drought tolerance was characterized by osmotic adjustment and higher relative leaf water content at low soil moisture levels. Furthermore, the findings of this study identify solute potential as an early predictor of drought stress tolerance. These intraspecific differences can be used in breeding programs for the development of drought-tolerant perennial ryegrass cultivars.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Radiation interception, radiation use efficiency (RUE) and harvest index (HI) are the key determinants of grain yield in cereal species. However, little is known about how these traits affect grain ...yield among spring wheat genotypes grown under low and optimum nitrogen (N) fertiliser supply. We used two experiments, in a field (Experiment 1; 2017-2018) and glasshouse (Experiment 2; 2018-2019) to investigate the effects of these traits on grain yield. Grain yield increased by 35% with increasing N fertiliser supply to 8.80 t/ha in Experiment 1 and 151% to 8.33 t/ha in Experiment 2. Grain yield was lowest for 'Reliance' and highest for 'Discovery' in both experiments. Differences in grain yield were not associated with HI. As the RUE did not differ among genotypes, the yield differences were attributed to the different amounts of radiation intercepted; a result of the faster leaf area expansion rate (LAER) and subsequent higher maximum green leaf area index (GLAI), and a longer leaf area duration (LAD). The differences in LAER and maximum GLAI among the genotypes were associated with a differences in specific leaf area (cm
2
/g). Our results suggest that improved grain yields in spring wheat can be achieved by focusing breeding efforts on canopy characteristics to increase radiation interception.
Atmospheric carbon dioxide concentrations (CO
2
) are increasing, but little is known about how this will affect macronutrient (nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and ...magnesium (Mg)) accumulation and partitioning in the aboveground biomass (AGB) for different hard spring wheat genotypes. We examined the responses of six spring wheat genotypes ('Discovery', 'Duchess', 'Reliance', PFR-3026, PFR-3019, PFR-2021) to two CO
2
levels (ambient aCO
2
and elevated eCO
2
) and six nitrogen rates (N; 1-10 mM), at the stem elongation growth stage of wheat grown in controlled environment chambers. The AGB yield increased by 35.2% with increasing CO
2
when N rate was >2 mM. Increasing N supply also increased AGB by up to 3.2-fold over the entire N range applied. The AGB responses to N differed among the genotypes, being lowest for PFR-3019 (7.71 ± 0.11 g/pot) and highest for PFR-2021, PFR-3026 and Duchess at 8.84 ± 0.11 g/pot at both CO
2
levels. Macronutrient concentrations decreased with eCO
2
by 28.0% for Ca to 17.4% for P and K. Nevertheless, absolute nutrient uptake was higher for eCO
2
treatments, because the AGB increase (20.0-52.0%) was proportionally higher than the 4.0-28.0% increase in nutrient uptake. The AGB non-response to CO
2
at N rates <2mM indicates that this nutrient deficiency was more limiting than the effects of CO
2
level
.
Therefore, the impact of eCO
2
in the future will depend on N fertilizer management. These results suggest that critical nutrient concentrations used to diagnose the nutrient status of wheat crops will need to be reassessed for eCO
2
conditions.
Seed production of four annual clover species, arrowleaf (Trifolium vesiculosum), balansa (Trifolium michelianum), gland (Trifolium glanduliferum) and Persian (Trifolium resupinatum) was quantified ...from four sowing dates in 2010. Following initial sowing rate at 4-6 kg/ha, these clovers produced seed yields up to ∼2340 kg/ha for balansa and gland, 914 kg/ha for arrowleaf and ∼814 kg/ha for Persian. After herbage was removed the clover seedlings that regenerated produced a maximum ground cover of 91% for balansa, 65% for gland, 17% for Persian and 6% for arrowleaf. The seeds of 'Mihi' Persian clover were all soft and none were recovered in the soil after three months of burial. In contrast, arrowleaf clover had the highest percentage of hardseededness (>97%) and therefore retained most of its viable seeds in the soil into the second year. The differences in hardseededness and regeneration potential mean different management strategies for their successful establishment into dryland farming systems.
Hydrothermal time (HTT) models describe the time course of seed germination for a population of seeds under specific temperature and water potential conditions. The parameters of the HTT model are ...usually estimated using either a linear regression, non-linear least squares estimation or a generalized linear regression model. There are problems with these approaches, including loss of information, and censoring and lack of independence in the germination data. Model estimation may require optimization, and this can have a heavy computational burden. Here, we compare non-linear regression with survival and Bayesian methods, to estimate HTT models for germination of two clover species. All three methods estimated similar HTT model parameters with similar root mean squared errors. However, the Bayesian approach allowed (1) efficient estimation of model parameters without the need for computation-intensive methods and (2) easy comparison of HTT parameters for the two clover species. HTT models that accounted for a species effect were superior to those that did not. Inspection of credibility intervals and estimated posterior distributions for the Bayesian HTT model shows that it is credible that most HTT model parameters were different for the two clover species, and these differences were consistent with known biological differences between species in their germination behaviour.
The Plant Modelling Framework (PMF) is a software framework for creating models that represent the plant components of farm system models in the agricultural production system simulator (APSIM). It ...is the next step in the evolution of generic crop templates for APSIM, building on software and science lessons from past versions and capitalising on new software approaches. The PMF contains a top-level Plant class that provides an interface with the APSIM model environment and controls the other classes in the plant model. Other classes include mid-level Organ, Phenology, Structure and Arbitrator classes that represent specific elements or processes of the crop and sub-classes that the mid-level classes use to represent repeated data structures. It also contains low-level Function classes which represent generic mathematical, logical, procedural or reference code and provide values to the processes carried out by mid-level classes. A plant configuration file specifies which mid-level and Function classes are to be included and how they are to be arranged and parameterised to represent a particular crop model. The PMF has an integrated design environment to allow plant models to be created visually. The aims of the PMF are to maximise code reuse and allow flexibility in the structure of models. Four examples are included to demonstrate the flexibility of application of the PMF; 1. Slurp, a simple model of the water use of a static crop, 2. Oat, an annual grain crop model with detailed growth, development and resource use processes, 3. Lucerne, perennial forage model with detailed growth, development and resource use processes, 4. Wheat, another detailed annual crop model constructed using an alternative set of organ and process classes. These examples show the PMF can be used to develop models of different complexities and allows flexibility in the approach for implementing crop physiology concepts into model set up.
•Next step in the evolution of crop modelling software in APSIM.•Designed to allow flexibility in the approach to construct different crop models without compiling source code.•Achieves extensive code re-use through generic organ and process classes and devolving calculations into function classes.•A set of 4 examples are given of crop models developed in this framework demonstrating its flexibility.
Liveweight production, dry matter yield and botanical composition of three lucerne based pastures (lucerne monoculture, lucerne/brome, lucerne/cocksfoot) were quantified for five years from a grazed, ...dryland experiment at Ashley Dene, Canterbury. The objective was to determine if liveweight production by sheep was enhanced by inclusion of a companion grass species with lucerne. Over five growth seasons (2012/2013-2016/2017) annual liveweight production ranged from 439 kg/ha (lucerne/grass mixes in 2016/2017) to 883 kg/ha (lucerne in 2013/2014). Liveweight produced from the monoculture was greater than, or equal to, that of the mixes every year. Dry matter yields ranged from 6.3 (lucerne and lucerne/cocksfoot in 2016/2017) to 16.2 t/ha/yr (lucerne in 2013/2014) primarily due to differences in in-season rainfall. Annual yield from the monoculture was less than, or equal to, lucerne/grass mixes in most years. The relationship between liveweight production and lucerne yield was strong (R
2
= 0.84). Earlier grazing of the mixes occurred in two of five years. After two years liveweight production from the lucerne/grass mixes was consistently lower than that achieved from the monoculture. However, in commercial situations drilling a runout lucerne stand with grass to extend stand life may be beneficial to provide an introductory feed prior to grazing a lucerne monoculture.
The New Zealand economy is export-driven and heavily reliant on the productivity of the pastoral sector. The transformation of native forest and tussock grassland ecologies to temperate grasslands ...occurred rapidly with the arrival of Europeans. However, this transplanted ecology required the development and use of plant, microbial, animal and management technologies for successful grassland farming. These have enabled New Zealand pastoral agriculture to compete effectively in international markets, without subsidies. The extensive list of plant-based and associated microbial-based adaptations, and the management strategies that have enabled the development of highly productive grasslands are described and reviewed. Credible science is required to inform the debate on the environmental impacts of pasture production to avoid misinformation proliferating. This needs transparent and objective integrity from the science community using funding that seeks no defined or preconceived outcomes. Critically, much of the success of New Zealand pastoral farming has been due to the willingness and ability of farmers to use, adapt, adopt and integrate new ideas and technologies into their farming systems. Historic, current and future challenges, and threats that impact on the productivity and sustainability of pastoral agriculture are described and the means to achieve further technology development to manage these is discussed.
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