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Background and Aims. Vineyard performance is impacted by water availability including the amount and seasonality of rainfall, evapotranspiration, and irrigation volume. We benchmarked water-limited yield potential (Yw), calculated yield gaps as the difference between Yw and actual yield, and explored the underlying environmental and management causes of these gaps. Methods and Results. The yield and its components in two sections of 24 Shiraz vineyards were monitored during three vintages in the Barossa zone (GI). The frequency distribution of yield was L-shaped, with half the vineyards below 5.2 t·ha−1, and an extended tail of the distribution that reached 24.9 t·ha−1. The seasonal ratio of actual crop evapotranspiration and reference evapotranspiration was below 0.48 in 85% of cases, with a maximum of 0.65, highlighting a substantial water deficit in these vineyards. A boundary function relating actual yield and seasonal rainfall was fitted to quantify Yw. Yield gaps increased with an increasing vine water deficit, as quantified by the carbon isotope composition of the fruit. The yield gap was smaller with higher rainfall before budburst, putatively favouring early-season vegetative growth and allocation to reproduction, and with higher rainfall between flowering and veraison, putatively favouring fruit set and berry growth. The gap was larger with higher rainfall and lower radiation between budburst and flowering. The yield gap increased linearly with vine age between 6 and 33 yr at a rate of 0.3 t·ha−1·yr−1. The correlation between yield gap and yield components ranked bunch weight ≈ berries per bunch > bunch number > berry weight; the minimum to close the yield gap was 185,000 bunches ha−1, 105 g bunch−1, 108 berries bunch−1, and 1.1 g berry−1. Conclusions. Water deficit and vine age were major causes of yield gaps. Irrigation during winter and spring provides an opportunity to improve productivity. The cost of dealing with older, less productive vines needs to be weighed against the rate of increase in yield gap with vine age. Significance of the Study. A boundary function to estimate water-limited yield potential returned viticulturally meaningful yield gaps and highlighted potential targets to improve vineyard productivity. [ABSTRACT FROM AUTHOR]

We review mechanisms for pre-emptive acclimation in plants and propose a conceptual model linking developmental and evolutionary ecology with the acquisition of information through sensing of cues and signals. The idea is that plants acquire much of the information in the environment not from individual cues and signals but instead from their joint multivariate properties such as correlations. If molecular signalling has evolved to extract such information, the joint multivariate properties of the environment must be encoded in the genome, epigenome, and phenome. We contend that multivariate complexity explains why extrapolating from experiments done in artificial contexts into natural or agricultural systems almost never works for characters under complex environmental regulation: biased relationships among the state variables in both time and space create a mismatch between the evolutionary history reflected in the genotype and the artificial growing conditions in which the phenotype is expressed. Our model can generate testable hypotheses bridging levels of organization. We describe the model and its theoretical bases, and discuss its implications. We illustrate the hypotheses that can be derived from the model in two cases of pre-emptive acclimation based on correlations in the environment: the shade avoidance response and acclimation to drought. [ABSTRACT FROM AUTHOR]

Water deficit often hastens flowering of pulses partially because droughted plants are hotter. Separating temperature-independent and temperature-dependent effects of drought is important to understand, model, and manipulate phenology. We define a new trait, drought effect on phenology (DEP), as the difference in flowering time between irrigated and rainfed crops, and use F ST genome scanning to probe for genomic regions under selection for this trait in chickpea (Cicer arietinum). Owing to the negligible variation in daylength in our dataset, variation in phenology with sowing date was attributed to temperature and water; hence, genomic regions overlapping for early- and late-sown crops would associate with temperature-independent effects and non-overlapping genomic regions would associate with temperature-dependent effects. Thermal-time to flowering was shortened with increasing water stress, as quantified with carbon isotope composition. Genomic regions on chromosomes 4–8 were under selection for DEP. An overlapping region for early and late sowing on chromosome 8 revealed a temperature-independent effect with four candidate genes: BAM1 , BAM2 , HSL2 , and ANT. The non-overlapping regions included six candidate genes: EMF1 , EMF2 , BRC1 / TCP18 , BZR1 , NPGR1 , and ERF1. Modelling showed that DEP reduces the likelihood of drought and heat stress at the expense of increased likelihood of cold stress. Accounting for DEP would improve genetic and phenotypic models of phenology. [ABSTRACT FROM AUTHOR]

Nitrogen availability and light quality affect plant resource allocation, but their interaction is poorly understood. Herein, we analyzed the growth and allocation of dry matter and nitrogen using lettuce (Lactuca sativa L.) as a plant model in a factorial experiment combining three light regimes (100% red light, R; 50% red light + 50% blue light, RB; 100% blue light, B) and two nitrogen rates (low, 0.1 mM N; high, 10 mM N). Red light increased shoot dry weight in relation to both B and RB irrespective of nitrogen supply. Blue light favored root growth under low nitrogen. Allometric analysis showed lower allocation to leaf in response to blue light under low nitrogen and similar leaf allocation under high nitrogen. A difference in allometric slopes between low nitrogen and high nitrogen in treatments with blue light reflected a strong interaction effect on root-to-shoot biomass allocation. Shoot nitrate concentration increased with light exposure up to 14 h in both nitrogen treatments, was higher under blue light with high nitrogen, and varied little with light quality under low nitrogen. Shoot nitrogen concentration, nitrogen nutrition index, and shoot NR activity increased in response to blue light. We conclude that the interaction between blue light and nitrogen supply modulates dry mass and nitrogen allocation between the shoot and root. [ABSTRACT FROM AUTHOR]

Clarifying the amount of pest damage that can be tolerated without justifying insecticidal control will be useful in reducing insecticide use and in development of integrated pest management (IPM) systems. This study investigated the ability of irrigated, high-yielding cotton (Gossypium hirsutum L.) to recover from artificially applied damage simulating that of early season insect pests. Six experiments were done across five cotton-growing seasons. Damage included defoliation, terminal damage, and flower bud removal in a range of timings, combinations, and intensities. Crop yield was unaffected by defoliation applied before first flower buds appeared, even when 100% of true leaves were removed on three occasions (Nodes 2, 4, and 6). Crop maturity was affected by sustained high levels of leaf loss with a peak delay of 10 d after 100% defoliation three times. Up to three light tip damage events or one heavy damage event had no effect on yield and only a slight effect on crop maturity (, COTTON IS ATTACKED by a range of insect pests, some of which are prevalent through the early portion of the growing cycle, such as tobacco thrips (Thrips tabaci Lindeman), tomato [...]

The combination of poorly drained soils and high rainfall can cause transient waterlogging and reduce yield of lentil. We screened 111 lentil lines for response to waterlogging in 2019 and 2020 using a pot assay outdoors. At 484 °Cd after emergence (38 d) in 2019 and 452 °Cd after emergence (42 d) in 2020, plants were waterlogged for 184 °Cd (11 d, 2019) and 167 °Cd (14 d, 2020) and allowed to recover for 323 °Cd (20 d, 2019) and 307 °Cd (26 d, 2020). We combined 2‐D digital images of canopy cover and plant height to derive a 3‐D trait that correlates with biomass to derive plant growth rate. Actual biomass at the end of recovery in the waterlogged plants varied 2.6‐fold with genotype, and genotypic and phenotypic correlations showed associations with plant growth rate both during (rg =.92; rp =.74) and after waterlogging (rg =.75; rp =.72); there was no trade‐off between maintenance of growth during waterlogging and growth during recovery. The ratio of biomass between waterlogged and control plants at the end of recovery was associated with growth rate during recovery (rg =.88, rp =.65) and biomass at the end of waterlogging (rg =.61, rp =.67). Broad‐sense heritability was 0.27 for growth rate during waterlogging, 0.37 for growth rate during recovery, 0.51 for biomass at the end of waterlogging and 0.47 for biomass at the end of recovery. High biomass at the end of recovery correlated with cooler canopies but correlations varied with season and measurement date, and heritability of canopy temperature was low. We identified genotypes with consistently higher tolerance to waterlogging and provide an improved understanding of the physiological response of lentil to hypoxia highlighting the importance of growth rate not only during waterlogging but also during recovery. [ABSTRACT FROM AUTHOR]

Technologies, from molecular genetics to precision agriculture, are outpacing theory, which is becoming a bottleneck for crop improvement. Here, we outline theoretical insights on the wheat phenotype from the perspective of three evolutionary and ecologically important relations—mother–offspring, plant–insect and plant–plant. The correlation between yield and grain number has been misinterpreted as cause-and-effect; an evolutionary perspective shows a striking similarity between crop and fishes. Both respond to environmental variation through offspring number; seed and egg size are conserved. The offspring of annual plants and semelparous fishes, lacking parental care, are subject to mother–offspring conflict and stabilizing selection. Labile reserve carbohydrates do not fit the current model of wheat yield; they can stabilize grain size, but involve trade-offs with root growth and grain number, and are at best neutral for yield. Shifting the focus from the carbon balance to an ecological role, we suggest that labile carbohydrates may disrupt aphid osmoregulation, and thus contribute to wheat agronomic adaptation. The tight association between high yield and low competitive ability justifies the view of crop yield as a population attribute whereby the behaviour of the plant becomes subordinated within that of the population, with implications for genotyping, phenotyping and plant breeding. [ABSTRACT FROM AUTHOR]

The objective of this study was to assess the ability of cotton (Gossypium hirsutum L.) crops to recover after early-season damage by thrips (Thysanoptera). Such information may help clarify the actual need to control thrips. Ten experiments, resulting from the combination of two to four sites per season and three seasons, were carried out in commercial crops in the irrigation area of northwest New South Wales, Australia. Two treatments were compared: unprotected crops and crops protected with aldicarb{2-methyl-2-(methylthio)propanal O-[(methylamino)carbonyl]oxime} at sowing. Early season thrips communities were dominated by Thrips tabaci Lindeman, which accounted for 52 to 100% of the total phytophagous thrips present in the crops. Insecticide treatment consistently reduced the number of larval thrips compared with the unprotected crops. Number of larval thrips per plant ranged from 0 to 24. Thrips reduced crop leaf area in six experiments, dry matter production in four experiments, and yield in two experiments. Maximum differences in leaf area and dry weight between treatments were found about 40 d after sowing. In all cases, crops damaged by thrips recovered well and reached leaf areas and dry weights similar to protected crops after about 60 to 80 d after sowing. On average, protected crops reached maturity 3 d earlier than crops damaged by thrips, but differences were not statistically significant. Despite large reductions in early growth, yield reductions due to thrips were found in only two experiments. The magnitude of the reduction in yield in those experiments (11%) contrasts with the magnitude of the reduction in growth (about 40%) and highlights the ability of the cotton crop to recover after early season damage by thrips., Young cotton crops host a range of insect pests, including thrips (Thysanoptera) (Hearn and Fitt, 1992). Common species of phytophagous thrips in high-input cotton cropping systems include Thrips tabaci and [...]

Foliar pests can affect reproductive allocation in plants. Depending on bow spider mites (Tetranychus urticae Koch) affect dry matter partitioning in cotton (Gossypium hirsutum L.), yield losses in infested crops could be similar, greater, or lower don expected from growth reduction. In this paper, we analyzed the effects of mite infestations initiated at three stages during the crop cycle on the yield, growth and dry matter partitioning of cotton. Normal- and okra-leaf types, which am known to differ in their responses to mites, were compared in two experiments. Lint yield losses were significant end were greatest for the earliest mute infestations. Reduced Shoot dry matter and reduced harvest index (lint yield/shoot dry matter) both contributed to these yield reductions. Yield losses were less severe in the okra-leaf cultivar than in its normal-leaf counterpart; this was in part due to a more favorable partitioning to key yield components in the former. to both experiments, reduced lint fraction [g lint [(g seed cotton).sup.-1] contributed to the lower harvest index of damaged crops. Reductions in both fruit number per unit shoot dry matter and seed cotton mass per fruit also contributed to reductions in harvest index of damaged crops. Despite the observed reductions in harvest index and some of its components, allometric analysis showed that mites did not affect partitioning to reproductive organs even in the more severely infested treatments. Rather, the low harvest index of mite-infested crops was the result of small plant sm. We conclude that mite effects on cotton growth and yield could be modelled by taking into account their primary effect on radiation-use efficiency and leaf senescence. Explicit modelling of the effects of mites on dry matter partitioning may not be necessary., Spider mites (Acari: Tetranychidae) can severely reduce cotton lint yield (Wilson, 1993, and references cited therein). Mite effects on yield are primarily related to reduction in shoot growth which is, [...]

Two-spotted spider mites Tetranychus urdow Kock) are important pests of cotton (Gossypium hirsutum L.). The effects of mites on cotton photosynthesis have been investigated at the leaf and cytological levels but not at the canopy level. Our objective was to quantify the effects of timing and intensity of infestation by mites on cotton radiation-use efficiency (RUE). Leaf area, light interception, RUE, canopy temperature, and leaf nitrogen concentration (LNC) were assessed during two growing seasons in crops artificially infested with miles between 59 and 127 d after sowing. Normal and okra-leaf cultivars were compared. A mite index (MI = natural log of the area under the curve of mite number vs thermal time) was used to quantify the cumulative effects of mites on RUE, LNC, and canopy temperature. Crop growth reduction due to mites was greater in early- than in late-infested crops. Growth reduction was primarily due to reductions in RUE, but in the more severe treatments accelerated leaf senescence and, henca, reduced light interception also contributed to reductions in crop growth. At a given date, infested okra-leaf crop usually had greater RUE than their normal-leaf counterparts. Both plant types, however, responded similarly to a given level of mite infestation. The ability of the okra-leaf cultivar to maintain greater RUE Levels can be attributed, therefore, to its relative inhospitality for the development of mite colonies rather than to an intrinsically greater capacity to maintain photosynthesis under mite damage. Canopy temperature, LNC, and RUE showed a similar, biphasic pattern of response to MI. In the first phase, response variables were almost unaffected by mites. In the second phase, there was a marked decline in RUE and LNC and a marked increase in canopy temperature with increasing MI. These results suggest (i) some degree of compensatory photosynthesis at low to moderate levels of mite infestation, and (ii) reductions in RUE of mite-infested cotton crops involved alterations in both canopy gas diffusion and metabolic activity. Quantitative relationships between RUE and MI were developed that could be used to link mite and crop growth models., Spider mites (Acari: Tetranychidae) are important secondary pests in cotton cropping systems which rely heavily on use of insecticides for the control of primary pests (Hearn and Fitt, 1992). While [...]

The evolution in the definition of crop yield—from the ratio of seed harvested to seed sown to the contemporary measure of mass of seed per unit land area―has favoured less competitive phenotypes. Here we use binary mixtures of cultivars spanning five decades of selection for yield and agronomic adaptation to ask three questions. First, what is the degree of symmetry in the response of yield to neighbour; this is, if an older, more competitive cultivar increases yield by 10% with a less competitive neighbour in comparison to pure stands, would the newer, less competitive cultivar reduce yield by 10% when grown with older neighbour. Lack of symmetry would indicate factors other than competitive ability underly yield improvement. Second, what are the yield components underlying competitive interactions. Third, to what extent are the responses to neighbour mediated by radiation, water and nitrogen. A focus on yield components and resources can help the interpretation of shifts in the crop phenotype in response to selection for yield. The rate of genetic gain in yield over five decades was 24 kg ha−1 year−1 or 0.61% year−1. A strongly symmetrical yield response to neighbour indicates that yield improvement closely associates with a reduction in competitive ability. Response to neighbour was larger for grain number and biomass than for grain weight and allocation of biomass to grain. Under our experimental conditions, competition for radiation was dominant compared to competition of water and nitrogen. High‐yielding phenotypes had lower competitive ability for radiation but compensated with higher radiation use efficiency, a measure of canopy photosynthetic efficiency. Genetic and agronomic manipulation of the crop phenotype to reduce competitive ability could further improve wheat yield to meet the challenge of global food security. [ABSTRACT FROM AUTHOR]

Wheat, rice, and maize collectively provide the bulk of energy and protein to the human diet worldwide. Over the last seven decades, China increased 5.8-fold the aggregated production of the three cereals, but further gains are required to meet the predicted demand of 776 Mt. by 2030. Here, we report the rate of genetic gain in yield of 0.65% year-1 for wheat between 1937 and 2012, 0.69% year-1 for rice between 1934 and 2011, and 0.77% year-1 for maize between 1950 and 2014 in China. National farm yield in the same periods increased 1.38% year-1 for wheat, 1.15% year-1 for rice and 1.32% year-1 for maize. Hence, genetic improvement (G) accounted for 47%-60% of the increase in farm yield, with improved management (M) and G × M interaction accounting for the balance. The absolute rate of genetic gain (kg ha-1 year-1) was proportional to environmental potential. Genetic gain in nitrogen utilization efficiency (yield per unit nitrogen uptake) was significant for all three crops and was achieved at the expense in grain N concentration that decreased at 0.19% year-1 in rice and 0.47% year-1 in maize. To guarantee future food security and environmental sustainability, breeding and agronomic efforts need to increase the rate of gain in yield and revert the declining trends in grain protein by improving nitrogen uptake and nitrogen harvest index. [ABSTRACT FROM AUTHOR]

The contemporary lentil (Lens culinaris ssp. culinaris) industry in Australia started in the late 1980s. Yield in farmers' fields averages 1.2 t ha–1 nationally and has not increased over three decades. Lack of yield progress can be related to a number of non-mutually exclusive reasons: expansion of lentil to low-yielding environments, lack of genetic gain in yield, lack of progress in agronomic practices, and lack of adoption of superior technologies. The aims of this study were to (i) quantify the genetic gain in lentil yield since 1988, (ii) explore the variation in the expression of genetic gain with the environment, and (iii) identify shifts in crop phenotype associated with selection for yield and agronomic adaptation. We grew a historic collection of 19 varieties released between 1988 and 2019 in eight environments resulting from the factorial combination of two sowing dates, two water regimes, and two seasons. Across environments, yield varied 11-fold from 0.2 to 2.2 t ha–1. The rate of genetic gain averaged 20 kg ha–1 year–1 or 1.23% year–1 across environments and was higher in low-yield environments. The yield increase was associated with substantial shifts in phenology. Newer varieties had a shorter time to flowering and pod emergence, and the rate of change in these traits was more pronounced in slow-developing environments (e.g., earlier sowing). Thermal time from sowing to end of flowering and maturity were shorter in newer varieties, and thermal time from pod emergence to maturity was longer in newer varieties; the rate of change in these traits was unrelated to developmental drivers and correlated with environmental mean yield. Genetic gain in yield was associated with increased grain number and increased harvest index. Despite their shorter time to maturity, newer varieties had similar or higher biomass than their older counterparts because crop growth rate during the critical period increased with the year of release. Genotype-dependent yield increased over three decades in low-yield environments, whereas actual farm yield has been stagnant; this suggests an increasing yield gap requiring agronomic solutions. Genetic improvement in high-yield environments requires improved coupling of growth and reproduction. [ABSTRACT FROM AUTHOR]

Science historian James Burke, scientist turned writer Isaac Asimov and polymath Stuart Kauffman have all argued, from different angles, that technology is unavoidable, directional, combinatory, disruptive and unpredictable. They also highlight the unintended consequences of technology seeking to fix a problem and creating new problems and opportunities. Here I draw on their vision to outline these features of technology with a focus on sustainable agriculture and highlight their implications for investment in research and development, and connecting public policy and technological change. [ABSTRACT FROM AUTHOR]

This article is part of a series of brief commentaries to highlight papers that have resulted in important and distinctly new perspectives in crop science. Here, we outline a series of two papers by French and Schultz (F&S) on water use efficiency of wheat (Triticum aestivum L.) published in 1984. The insight of F&S was not to draw a regression line across their yield‐evapotranspiration data. Instead they saw an upper limit of 20 kg ha−1 mm−1 that, less than a decade after publication, was widely used by Australian farmers to benchmark their crops and identify causes of yield gaps. Over the last two decades, F&S‐type benchmarks have been expanded beyond wheat and beyond Australia to include sunflower (Helianthus annuus L.) in Argentina, maize (Zea mays L.) and wheat in the United States and China, and millet [Pennisetum glaucum (L.) R. Br.] in West Africa, among others. More recently, the concept of yield gap analysis based on a upper limit of yield per unit resource uptake has been successfully extrapolated to N. The N uptake per millimeter of water required to meet the water‐limited yield potential (0.65 kg N ha−1 mm−1 under their original conditions) is a hidden insight in the work of French and Schultz; it has been recently rediscovered in the context of crop improvement, co‐limitation theory, and drought‐induced N deficit. Perhaps more deeply, French and Schultz shifted farmers mindset from the mildly fatalistic idea of "drought" to the notion that many other factors were typically limiting crop yield, and the quantitative challenge of attaining a plausible benchmark. [ABSTRACT FROM AUTHOR]

Nonstructural carbohydrates in cereals have been widely investigated from physiological, genetic, and breeding perspectives. Nonstructural carbohydrates may contribute to grain filling, but correlations with yield are inconsistent and sometimes negative. Here we ask if there are hidden functions of nonstructural carbohydrates, advance an ecological dimension to this question, and speculate that high concentration of nonstructural carbohydrates may challenge the osmotic homeostasis of aphids, thus providing a working hypothesis that connects nonstructural carbohydrates with aphid resistance in cereals. In the light of this proposition, the amount and concentration of nonstructural carbohydrates should be regarded as functionally different traits, with amount relevant to the carbon economy of the crop and concentration playing an osmotic role. We conclude with suggestions for experiments to test our hypothesis. [ABSTRACT FROM AUTHOR]

How does a trait measured in an individual plant relate to the trait in a crop stand, where yield and other agronomic attributes are resolved? Seeding rate effects on tillering, grain yield, and yield components of oat at high latitude. Scaling, yield, density-dependence, phenotype, context-dependence. [Extracted from the article]

Highlights • Genetic gains of Australian wheat were associated with higher water-nitrogen co-limitation. • Higher water-nitrogen co-limitation associated with a higher nitrogen uptake per unit of evapotranspiration. • Nitrogen traits are critical for drought adaptation. Abstract The interactions between nitrogen (N) and water are manifold, and the concept of co-limitation provides a quantitative framework for integration. This paper tested the hypothesis that selection for yield increased water-N co-limitation in wheat adapted to winter rainfall environments of Australia. To test this hypothesis, we measured evapotranspiration, N uptake and yield in a historic collection of varieties released between 1958 and 2007 (exp. 1) and between 1969 and 2015 (exp. 2). Crops were grown under 5 (exp. 1) or 4 (exp. 2) environmental conditions resulting from the combination of sites, seasons, and supply of N and water. Genetic gain of yield, i.e. the slope of the regression between yield and year of release was 14–24 kg ha−1 y−1 or 0.36–0.52% y−1. This yield gain was associated with a linear increase in water-N co-limitation, in turn associated with an increase in N uptake per mm of evapotranspiration at a rate of 0.0019 kg N mm−1 y−1. Our findings highlight the critical role of nitrogen for the adaptation of wheat to low rainfall environments, and the scope for further yield improvement based on traits that integrate resources. [ABSTRACT FROM AUTHOR]

Blue light and UV radiation shape a plant's morphology and development, but accession-dependent responses under natural conditions are unclear. Here we tested the hypothesis that two faba bean (Vicia faba L.) accessions adapted to different latitudes and altitudes vary in their responses to solar blue and UV light. We measured growth, physiological traits, phenolic profiles and expression of associated genes in a factorial experiment combining two accessions (Aurora, a Swedish cultivar adapted to high latitude and low altitude; ILB938, from the Andean region of Colombia and Ecuador, adapted to low latitude and high altitude) and four filter treatments created with plastic sheets: 1. transparent as control; 2. attenuated short UV (290–350 nm); 3. attenuated UV (290–400 nm); 4. attenuated blue and UV light. In both accessions, the exclusion of blue and UV light increased plant height and leaf area, and decreased transcript abundance of ELONGATED HYPOCOTYL 5 (HY5) and TYROSINE AMINOTRANSFERASE 3 (TAT3). Blue light and short UV induced the accumulation of epidermal and whole-leaf flavonoids, mainly quercetins, and the responses in the two accessions were through different glycosides. Filter treatments did not affect kaempferol concentration, but there were more tri-glycosides in Aurora and di-glycosides in ILB938. Furthermore, fewer quercetin glycosides were identified in ILB938. The transcript abundance was consistently higher in Aurora than in ILB938 for all seven investigated genes: HY5, TAT3, CHALCONE SYNTHASE (CHS), CHALCONE ISOMERASE (CHI), DON-GLUCOSYLTRANSFERASE 1 (DOGT1), ABA INSENSITIVE 2 (ABI2), AUXIN-INDUCIBLE 2–27 (IAA5). The two largest differences in transcript abundance between the two accessions across treatments were 132-fold in CHS and 30-fold in DOGT1 which may explain the accession-dependent glycosylation patterns. Our findings suggest that agronomic selection for adaptation to high altitude may favour phenotypes with particular adaptations to the light environment, including solar UV and blue light. [ABSTRACT FROM AUTHOR]

Highlights • Root pruning improved wheat grain yield, HI and WUE by 6–11%. • Root pruning in spring performed better than that in winter. • Root pruning was more effective at high seeding rate in low-yielding conditions. • Root pruning improved apparent translocation of water soluble carbohydrates. Abstract Improved management practices are necessary to increase grain yield and water-use efficiency of rainfed winter wheat in semiarid environments. Yield and its components, evapotranspiration, and accumulation and apparent remobilisation of stem water soluble carbohydrates (WSC) were measured to understand the effects of root pruning and its interactions with seeding rate, water and nitrogen supply. Two factorial studies under straw mulching with continuous wheat were established in the Loess Plateau of China. Study 1 was repeated over four seasons and included six treatments from the combination of three root treatments, i.e. root pruning in winter before dormancy (RPw), root pruning at the re-green stage in spring (RPs) and untreated control (CK), and two seeding rates. Study 2 was repeated over three seasons and included twelve treatments from the combination of two root treatments (RPs and CK), two nitrogen rates and three pre-sowing soil water levels. Yield ranged from 2571 to 7722 kg ha−1, harvest index from 0.28 to 0.56, and water-use efficiency from 5 to 20 kg ha−1 mm−1. Root pruning improved grain yield, harvest index and water-use efficiency by 6–11% across environmental conditions. Grain yield increased more (i) by pruning roots in spring than in winter, (ii) in high plant density than in low plant density crops, and (iii) in low-yielding conditions. It is concluded that spring root pruning is a viable option to improve wheat yield and water use efficiency under straw mulching in semiarid environment. [ABSTRACT FROM AUTHOR]