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Highlights • Ecological intensification management (EI) was compared with average farmer practice (FP). • We evaluated resource productivity and its components at the crop sequence level. • Water and radiation productivities were higher in EI than in FP. • Resource use efficiencies increased more than resource capture in EI as compared with FP. • The EI management reduced partial factor productivity of applied N but improved the partial N balance. Abstract The challenge to increase agricultural production with a minimum environmental impact requires to reach the maximum efficiency in the capture and use of resources such as photosynthetically active radiation (PAR), water, and nitrogen (N). Such requisites are encompassed in the ecological intensification (EI) concept. The aims of this work were to evaluate at a crop sequence level: i) crops yields, ii) water and radiation productivity and its components, i.e. resource capture and resource use efficiency, and iii) partial factor productivity of applied N (PFPN), partial nutrient balance for N (PNB), N uptake and N utilization efficiency of a two-year, three-crop sequence (wheat [ Triticum aestivum L.]/soybean [ Glycine max (L.) Merr.] double crop – maize [ Zea mays L.]) carried-out under EI principles in comparison with the same crop sequence under current farmer practices (FP) in two contrasting locations of the Argentinean Pampas, i.e. Paraná (-31°50′; -60°31′) at the northern Pampas and Balcarce (-37°45′, -58°18′) at the southern Pampas. Experiments were carried-out during four consecutive years, covering two complete cycles of the crop sequence. For the accumulated grain production of the crop sequence, EI management outyielded FP from 13 to 42%, depending on environmental conditions. Maize yield accounted for most of the variation (41–64%) of the accumulated grain yield of crop sequence, whether in EI as in FP. Average grain yield differences between EI and FP treatments were 274 g m−2 for maize, 69 g m−2 for wheat and -2 g m−2 for soybean. Water and radiation productivities of the sequence were higher in EI than in FP (26% for water and 17% for radiation; P < 0.0001), mainly because of increases in resource use efficiencies. EI reduced partial factor productivity of applied N, but improved partial nutrient balance for N as compared with FP. These reductions in partial factor productivity of applied N were less than proportional than the increases in N rate. Moreover, in spite of the higher N rate in EI respect to FP, N utilization efficiency (N ut E), i.e. grain per unit N uptake, was higher across all situations in EI. Our results showed that the challenge to obtain high grain yields by increasing N rate in a medium-input system could be achieved even with an increase in N ut E. Grain yields improvements, and increases in radiation and water productivity were reached by applying a set of agronomic practices that included improved genetics, crop and fertilizer N management englobed under EI concept. [ABSTRACT FROM AUTHOR]

Mixed-species growth models are needed as a synthesis of ecological knowledge and for guiding forest management. Individual-tree models have been commonly used, but the difficulties of reliably scaling from the individual to the stand level are often underestimated. Emergent properties and statistical issues limit their effectiveness. A more holistic modelling of aggregates at the whole stand level is a potentially attractive alternative. This work explores methodology for developing biologically consistent dynamic mixture models where the state is described by aggregate stand-level variables for species or age/size cohorts. The methods are demonstrated and tested with a two-cohort model for spruce–aspen mixtures named SAM. The models combine single-species submodels and submodels for resource partitioning among the cohorts. The partitioning allows for differences in competitive strength among species and size classes, and for complementarity effects. Height growth reduction in suppressed cohorts is also modelled. SAM fits well the available data, and exhibits behaviors consistent with current ecological knowledge. The general framework can be applied to any number of cohorts, and should be useful as a basis for modelling other mixed-species or uneven-aged stands. [ABSTRACT FROM AUTHOR]

Integrated crop-livestock systems (ICL) have played an important role in human civilisation and have dominated the broadacre agricultural production system in the wheat-sheep zone of Australia. Over the past couple of decades, an increase in grain prices and decline in wool prices have led to the expansion of cropping into the high rainfall zone (HRZ) in southern Australia. While there has been a great deal of research into integrated crop-livestock systems for the medium to low rainfall environments in the wheat-sheep zone, there is much less information and many challenges confronting farmers to effectively integrate crops into the grazing systems in the high rainfall zone due to climatic and environmental differences and the complexity of the systems in Australia. This paper reviews the benefits of integrated crop-livestock systems and the challenges in implementing and managing these systems based on current Australian and international knowledge. The concept, types and terminology of integrated crop-livestock systems are discussed to provide greater clarity. Plant species, particularly annual and perennial legumes, are reviewed to find species with potential for use in integrated crop-livestock systems. Major gaps and opportunities for further research and development are identified, and recommendations proposed for developing effective integrated crop-livestock systems for the HRZ. These include: 1) Targeted R&D on ICL systems in the HRZ of southern Australia assisted with information from and outside Australia; 2) Biophysical and bio-economic modelling using current knowledge from the HRZ and other environments to guide future research; 3) Studies on N fixation, transfer and losses to develop strategies to balance N cycling and reduce N losses; 4) Development of compatible species/cultivars for ICL systems in the HRZ; 5) Management of waterlogging through ICL in the HRZ; 6) Effective stubble management to minimise the negative impact on crops and pastures; 7) Integrated research on grain yield reduction in crop-pasture intercropping, a potentially major type of ICL systems in the HRZ; and 8) Effective control of weeds, pests and diseases in ICL systems for the HRZ. [ABSTRACT FROM AUTHOR]

Intercropping is a common practice in low productivity (low input–low output) small-scale farming systems. However, as the level of productivity increases due to technological improvements whether intercropping – compared to sole cropping – remains the most productive and resource efficient cropping system is not well understood. Here we hypothesize that inter-crops outperform sole crops at low levels of resource availability because of improved resource capture and resource use efficiency; and answered whether this advantage decreases with increasing levels of resource availability. The performance of three cropping systems i.e. maize intercropped with navy bean, sole maize and sole navy bean were evaluated at three levels of resource input i.e. a low water/nitrogen (low W/N), a medium water/nitrogen (medium W/N), and a high water/nitrogen (high W/N), in three independent experiments, conducted over two consecutive years. The performance of the cropping systems was evaluated in terms of land equivalent ratios (LER), total grain yield, protein and energy productions as well as resource (water, nitrogen, and solar radiation) capture and use efficiency. Our results indicate that maize productivity (grain yield, protein and energy productions) was not significantly affected by the intercrop at any level of resource availability. However, irrespective of the level of resource input, intercropping significantly reduced the productivity of navy bean. The advantage of the intercropping, in terms of LER, tended to decrease with increasing the level of water and nitrogen supply i.e. decreased from 28% to 6% for above ground biomass, from 40% to 7% for grain yield, from 41% to 0.3% for protein production and from 40% to 9.2% for energy production. Intercropping was therefore more efficient in terms of LER under low W/N than under high W/N conditions. The LER was directly related to improved capture of nitrogen and to higher water use efficiency. Here we conclude that in terms of LER, intercropping systems are more resource efficient and suitable for lower productivity environments. As more productive technologies are adopted by smallholder farmers, agricultural development projects and extension services need to consider under what conditions sole cropping become a more productive system. [ABSTRACT FROM AUTHOR]

Abstract: Crops respond to N deficiency through a reduction in resource capture and/or resource use efficiency. The objective of this paper is to examine whether differences in this response pattern are associated with either metabolic group (C3 vs. C4) or botanical classification (mono- vs. dicotyledons). Hereto, we analysed the effect of N deficiency on the relationships between N uptake, LAI, and biomass accumulation, for maize, sorghum, wheat, canola, tall fescue, and sunflower, grown in experiments in either France or Australia. Maize and tall fescue maintained LAI per unit biomass (measure of resource capture) at the expense of N uptake per unit LAI (measure of resource use efficiency). Wheat and canola had the opposite response, whereas sunflower and sorghum were intermediate. In general, C4 species reduced N uptake per unit LAI more than C3 species. Species differences in the effect of N deficiency on resource use efficiency were associated with differences in the SLN or in the N storage capacity of the stems. For wheat, canola, and tall fescue, SLN declined with increasing LAI under high N conditions, and the minimum crop SLN under N deficiency was only marginally lower than under high N conditions. For sorghum, sunflower, and maize, crop SLN under high N changed little with increasing LAI, but the minimum crop SLN under N deficiency was considerably lower than under high N. Sorghum and maize were the only species that substantially decreased stem N uptake per unit LAI under N deficiency. Overall, our data suggest that C3 species are better able to maintain resource use efficiency under N stress than C4 species, and a survey of literature suggests this may be because in C4 species, the critical SLN for radiation use efficiency is higher than the critical SLN for leaf expansion, whereas the opposite is the case for C3 species. We hypothesise that species differences in response to N deficiency could be associated with these differences in critical SLN, which in turn could be a consequence of the lower photosynthetic nitrogen use efficiency of C3 crops. [Copyright &y& Elsevier]

Abstract: We tested the hypotheses that invasive species had higher irradiance plasticity, capture ability and efficiency than noninvasive species using two invasive aliens –Ageratina adenophora and Chromolaena odorata, and one noninvasive alien –Gynura sp. The three aliens were grown at 4.5%, 12.5%, 36%, 50% and 100% irradiances for 64 days before harvesting. The plastic response of specific leaf area (SLA) contributed to improved light interception at low irradiance, carbon gain and water balance at high irradiance. It was a good predictor for intraspecific irradiance responses of leaf area ratio (LAR), leaf area:root mass ratio, maximum photosynthetic rate (P max) and net assimilation rate (NAR). Biomass allocation-related traits were species specific and their plasticity to irradiance was low. The high root mass fraction, leaf mass fraction and LAR distinguished the two invaders from Gynura. However, other resource capture-related traits, such as SLA, NAR and P max, were not always higher for the invaders than for Gynura. Furthermore, plasticity to irradiance was not different between the invasive and noninvasive aliens. With increasing irradiance, Gynura decreased biomass investment to roots and leaves but increased the investment to support structures adversely affecting both low and high irradiance acclimation. Ageratina might invade new habitat successfully through tolerating shading at low irradiance and outshading competitors by forming dense stands when irradiance is increased. The results suggested that both resource capture-related traits and irradiance acclimation conferred competitive advantage to the two invaders and some traits were common for invasive and noninvasive aliens but others were specific for invaders. [Copyright &y& Elsevier]

Abstract: The functional structural tree growth model ALMIS uses the individual based modelling approach and is implemented in the object-oriented programming language SIMULA. All features (state variables) and functions (processes) are specified locally, on the level of the single plant organs. Increasing numbers of “copies” (objects) of these elementary units, Internodes, Leaves, Meristems, Roots, and Root tips, form the growing tree. Various procedures (e.g. Photosynthesis, Nutrient_uptake, Transport, Storage, Mobilisation, Respiration, Growth) are employed to describe carbon and nutrient uptake, and matter fluxes between the different plant organs. Combining plant physiology and architecture, ALMIS allows studying the effect of single ecophysiological and structural processes on whole tree growth and in the tree–environment system. Some of these effects, driven by microclimate, self-shading, variable nutrient availability, variable transport dynamics, and branching patterns are exemplified. From the interactions at the organ and sub-organ levels new features emerge at higher levels of plant organisation. These so-called emergent properties are, for example, lifetime spectrum of single organs, space filling (“architecture”) and self-thinning of the crown. The most prominent emergent properties are the different growth forms of trees resulting from simulations under various conditions. Their causal interrelations are discussed in detail. [Copyright &y& Elsevier]