Yield Penalty Research Articles

Multi-Omics Analysis Reveals Synergistic Enhancement of Nitrogen Assimilation Efficiency via Coordinated Regulation of Nitrogen and Carbon Metabolism by Co-Application of Brassinolide and Pyraclostrobin in Arabidopsis thaliana.

Improving nitrogen (N) assimilation efficiency without yield penalties is important to sustainable food security. The chemical regulation approach of N assimilation efficiency is still less explored. We previously found that the co-application of brassinolide (BL) and pyraclostrobin (Pyr) synergistically boosted biomass and yield via regulating photosynthesis in Arabidopsis thaliana. However, the synergistic effect of BL and Pyr on N metabolism remains unclear. In this work, we examined the N and protein contents, key N assimilatory enzyme activities, and transcriptomic and metabolomic changes in the four treatments (untreated, BL, Pyr, and BL + Pyr). Our results showed that BL + Pyr treatment synergistically improved N and protein contents by 56.2% and 58.0%, exceeding the effects of individual BL (no increase) or Pyr treatment (36.4% and 36.1%). Besides synergistically increasing the activity of NR (354%), NiR (42%), GS (62%), and GOGAT (62%), the BL + Pyr treatment uniquely coordinated N metabolism, carbon utilization, and photosynthesis at the transcriptional and metabolic levels, outperforming the effects of individual BL or Pyr treatments. These results revealed that BL + Pyr treatments could synergistically improve N assimilation efficiency through improving N assimilatory enzyme activities and coordinated regulation of N and carbon metabolism. The identified genes and metabolites also informed potential targets and agrochemical combinations to enhance N assimilation efficiency.

Residue recycling options and their implications for sustainable nitrogen management in rice–wheat agroecosystems

BackgroundIn the Indo-Gangetic Plain, rice–wheat is the most extensively practiced crop rotation. The escalating issue of crop residue burning, particularly rice straw, and the necessity to lower the exorbitant expenses associated with fertilizer inputs stand out as significant challenges for farmers in the region. A well-suited integrated nutrient management (INM) strategy that focuses on recycling crop residues can serve as a solution to address these issues. Such a strategy not only mitigates air pollution resulting from residue burning but also helps combat water pollution due to nitrate losses from agroecosystems. Field experiments were used to evaluate the suitability of eight INM-modules that included various combinations of inorganic fertilizer rates (50%, 100%, 150% of recommended dose), crop residues (wheat and rice stubble retention at 30 cm standing stubble equivalent to 1/3 the straw yield), rice straw compost (RSC), farmyard manure (FYM), and green manuring (GM), compared to 100% recommended dose of fertilizers (F) and no fertilizer application.ResultsThere was a considerable improvement in nitrogen mineralization, grain yields, and nitrogen use efficiency under GM + RSC-F50 and GM + FYM-F50. These INM modules would permit a 50% reduction in the use of chemical fertilizers. There was a little yield penalty with in situ rice residue incorporation at 100% F; however, this could be overcome with 150% F fertilizer application. In situ retention of wheat straw with a full application of fertilizer resulted in steadily rising crop yields over time. Changes in the redox potential, soil pH, and soil organic carbon best accounted for the observed trajectories in nitrogen use efficiency.ConclusionThe most promising INM modules for adoption by farmers in the Indo-Gangetic Plain to judiciously use crop residues and curtail chemical fertilizer inputs are green manuring with Sesbania aculeata + rice straw compost at 5 t ha−1 + only 50% of recommended dose of fertilizers (GM + RSC-F50), and green manuring with Sesbania aculeata + farmyard manure at 5 t ha−1 + only 50% of recommended dose of fertilizers (GM + FYM-F50). Sole incorporation of crop residues without nitrogen augmentation from other sources might not help curtail chemical fertilizer use. Composting rice straw, which otherwise is widely burnt, proved a useful nitrogen source and a vital component of INM. Waste rice straw composting at the community scale and its application as a nutrient source can help achieve sustainable nitrogen management in the agroecosystems of Indo-Gangetic Plain.

Testing for complementarity between the use of continuous no-till and cover crops: An application of entropy approach

The carbon sequestration and overall crop production sustainability benefits of no-till (NT) farming are fully realized only when NT is used continuously over several years. Research shows that most U.S. farmers do not use the practice continuously. One of the commonly suggested reasons for intermittent tillage is the risk of a significant yield penalty during the first several years after converting to continuous no-till (CNT). Agronomic research suggests that continuous cover crops (CCR) can be both an economical and biological answer to the risk of yield reduction associated with the use of CNT, as CCR accelerates the processes of converting and storing nitrogen in the soil and improves soil structure and water infiltration. However, whether farmers consider the complementary benefits of CNT and CCR is largely unknown. The objective of this study is to test the complementarity between the uses of the two conservation practices in the State of Indiana, U.S. We combine Quadratic Programming and Entropy approaches to estimate 1st-order Markov transition matrices for tillage and cover crops dynamic models, respectively. Then, we apply Bayes' theory to test the complementarity. The data used for the analysis come from the Conservation Tillage Information Center and Indiana Tillage and Cover Crops Transect, 1992–2019. The findings show that there is no evidence supporting complementarity between the use of CNT and CCR in Indiana. The results also show that the use of CCR in the State is growing steadily at a rate of approximately 30% during 2011–2015 and then stabilize during 2016–2019, whereas the share of land allocated to CNT remains flat in the same period. In addition to being the first formal test of the complementarity between the uses of the two sustainable crop production practices, the novelty of our contribution relates to the econometric methodology and the data. We introduce an approach for estimating dynamic models of farmers' yearly choices and demonstrate the possibility of testing for complementarity between the choices with very limited – aggregated and missing – data.

Multi-environment screening of Linum germplasm collection for dissecting the potential of bud fly (Dasyneura lini Barnes) resistance and assembling a reference set for efficient utilization in genetic improvement

Linseed or flaxseed (Linum usitatissimum L.) is one of the most ancient industrial crops domesticated for oil and natural fiber. Bud fly (Dasyneura lini Barnes) susceptibility is serious biotic stress affecting its production both quantitatively and qualitatively. It has economic significance particularly in Asian countries, causing substantial crop damage leading to significant yield penalty and deterioration of seed quality. In the present study, a large collection of 2598 linseed germplasm accessions from the Indian National Genebank were screened for bud fly infestation at two natural hot-spot locations in India. The maximum bud fly incidence across all four environments ranged from 47.93% to 90.47%. Based on average bud fly infestation over the environments, a reference set comprising 195 accessions including 46 resistant, 94 moderately resistant and 55 moderately susceptible/susceptible germplasm was developed. Further, a selected subset of 26 accessions having a common reaction against linseed bud fly at both locations was validated for resistance over multi-location-year environments (four environments over two years) through GGE biplot analysis. The GGE biplot revealed that two accessions, G22 (EC0993391) and G23 (IC0633096) were highly resistant (<10% bud fly damage) and most stable over the tested environments against bud fly infestation. Additionally, two accessions namely G15 (IC0498795) and G24 (EC0099001) were considered resistant as they showed consistent performance and low bud fly infestation in comparison to the resistant check (Neela). Moreover, these accessions had a great buffering capacity to perceive environmental signals for developing adaptive capacities in a wide range of environments. The identified germplasm accessions may serve as potential donors for accelerating the resistance breeding programme to impart a long-lasting, broad-spectrum resistance against linseed bud fly.

The potential for mitigating greenhouse gas emissions and minimizing yield losses using the negative pressure irrigation system

Efficient strategies for reducing agricultural greenhouse gas (GHG) emissions without yield penalties are crucial for sustainable agricultural development in the context of population increases and global warming. This study investigates the efficacy of negative pressure irrigation (NPI) in mitigating GHG emissions, as well as its impact on crop yield, global warming potential (GWP), and GHG emission intensity (GHGI), using surface irrigation (CK) as the control. The NPI system operated at three water pressure levels: NPI1 (-2 kPa), NPI2 (-4 kPa), and NPI3 (-6 kPa). The results revealed a notable pattern under NPI: a single peak in GHG emissions that remained consistently, and much lower than CK for the majority of the vegetable season, directly results in the lower cumulative GHG emissions and GWP from NPI than those from CK. Notably, the central region, located near the emitter, exhibited significantly lower GWP compared to the edge region, accompanied by higher yields, leading to a lower GHGI. Based on the findings, the -2 kPa water pressure level demonstrated the optimal performance in sustaining crop yields for Chinese chives while effectively reducing GWP and GHGI. Additionally, regions situated 20 cm on both sides of the emitter under -2 kPa NPI were identified as suitable areas for crop cultivation, offering higher yields and lower GWP and GHGI compared to CK. These results emphasize the win-win situation by balancing vegetable yield while reduced GHG emissions.

Individual and combined influences of salinity and drought stress on the agro-physiological traits and grain yield of rice

Because of inadequate water resources and poor irrigation facilities, salinity and drought stresses often co-occur in rice production in saline lands. Nevertheless, little information is available on the agro-physiological traits and grain yield of rice when subjected to combined salinity × drought stress. We evaluated the individual and interactive influences of salinity and drought on rice yield and agro-physiological characteristics using two rice cultivars, Nanjing 9108 (salinity-tolerant rice) and Wuyunjing 30 (salinity-susceptible rice). This experiment was conducted under non-salinity (NS) and salinity (S) conditions and three drought levels from jointing to heading (CC, control condition; MD, moderate drought; SD, severe drought). Individual salinity and drought treatments and their combination shortened the total growth duration by 3–4 days and 4–6 days in Nanjing 9108 and Wuyunjing 30, respectively. Both salinity and drought treatments reduced (P < 0.01 or P < 0.05) rice yield by 12.9%−40.9% and 28.1%−35.0% across the two cultivars, respectively, and the combined salinity × drought treatment resulted in a more pronounced yield loss of 53.1%−113.3%. A greater reduction in grain yield caused by the combined salinity × drought stress was detected in Wuyunjing 30 than in Nanjing 9108. The poor grain yield performance of rice under combined salinity × drought stress was mainly attributable to the following: (1) yield components, panicle length, and single panicle weight were lower than they were under an individual stress; (2) combined stress caused greater reductions in shoot biomass, leaf area index (LAI), and nonstructural carbohydrate (NSC) content in the stem at heading and maturity, although harvest index and NSC remobilization reserve were increased; (3) each stress and especially combined stress increased Na+/K+ ratio in the leaf, while reducing leaf photosynthetic rate and SPAD values after heading, and total accumulation of nitrogen (N), phosphorus (P), and potassium (K). Our results suggested that the combined salinity × drought stress was more damaging than either stress alone, and resulted in a greater yield penalty of rice. In terms of grain yield, salinity-susceptible rice was more responsive to the combined stress than salinity-tolerant rice.

The cytoprotective co-chaperone, AtBAG4, supports increased nodulation and seed protein content in chickpea without yield penalty

Drought and extreme temperatures significantly limit chickpea productivity worldwide. The regulation of plant programmed cell death pathways is emerging as a key component of plant stress responses to maintain homeostasis at the cellular-level and a potential target for crop improvement against environmental stresses. Arabidopsis thaliana Bcl-2 associated athanogene 4 (AtBAG4) is a cytoprotective co-chaperone that is linked to plant responses to environmental stress. Here, we investigate whether exogenous expression of AtBAG4 impacts nodulation and nitrogen fixation. Transgenic chickpea lines expressing AtBAG4 are more drought tolerant and produce higher yields under drought stress. Furthermore, AtBAG4 expression supports higher nodulation, photosynthetic levels, nitrogen fixation and seed nitrogen content under well-watered conditions when the plants were inoculated with Mesorhizobium ciceri. Together, our findings illustrate the potential use of cytoprotective chaperones to improve crop performance at least in the greenhouse in future uncertain climates with little to no risk to yield under well-watered and water-deficient conditions.

Crop sensitivity to waterlogging mediated by soil temperature and growth stage.

Waterlogging constrains crop yields in many regions around the world. Despite this, key drivers of crop sensitivity to waterlogging have received little attention. Here, we compare the ability of the SWAGMAN Destiny and CERES models in simulating soil aeration index, a variable contemporaneously used to compute three distinct waterlogging indices, denoted hereafter as WI Destiny, WIASD1, and WIASD2. We then account for effects of crop growth stage and soil temperature on waterlogging impact by introducing waterlogging severity indices, WI Growth, which accommodates growth stage tolerance, and WI Plus, which accounts for both soil temperature and growth stage. We evaluate these indices using data collected in pot experiments with genotypes "Yang mai 11" and "Zheng mai 7698" that were exposed to both single and double waterlogging events. We found that WI Plus exhibited the highest correlation with yield (-0.82 to -0.86) suggesting that waterlogging indices which integrate effects of temperature and growth stage may improve projections of yield penalty elicited by waterlogging. Importantly, WI Plus not only allows insight into physiological determinants, but also lends itself to remote computation through satellite imagery. As such, this index holds promise in scalable monitoring and forecasting of crop waterlogging.

A novel natural variation in the promoter of GmCHX1 regulates conditional gene expression to improve salt tolerance in soybean.

Identification and characterization of soybean germplasm and gene(s)/allele(s) for salt tolerance is an effective way to develop improved varieties for saline soils. Previous studies identified GmCHX1 (Glyma03g32900) as a major salt tolerance gene in soybean, and two main functional variations were found in the promoter region (148/150 bp insertion) and the third exon with a retrotransposon insertion (3.78 kb). In the current study, we identified four salt-tolerant soybean lines, including PI 483460B (Glycine soja), carrying the previously identified salt-sensitive variations at GmCHX1, suggesting new gene(s) or new functional allele(s) of GmCHX1 in these soybean lines. Subsequently, we conducted quantitative trait locus (QTL) mapping in a recombinant-inbred line population (Williams 82 (salt-sensitive) × PI 483460B) to identify the new salt tolerance loci/alleles. A new locus, qSalt_Gm18, was mapped on chromosome 18 associated with leaf scorch score. Another major QTL, qSalt_Gm03, was identified to be associated with chlorophyll content ratio and leaf scorch score in the same chromosomal region of GmCHX1 on chromosome 3. Novel variations in a STRE (stress response element) cis-element in the promoter region of GmCHX1 were found to regulate the salt-inducible expression of the gene in these four newly identified salt-tolerant lines including PI 483460B. This new allele of GmCHX1 with salt-inducible expression pattern provides an energy cost efficient (conditional gene expression) strategy to protect soybean yield in saline soils without yield penalty under non-stress conditions. Our results suggest that there might be no other major salt tolerance locus similar to GmCHX1 in soybean germplasm, and further improvement of salt tolerance in soybean may rely on gene-editing techniques instead of looking for natural variations.

Genome editing creates disease-resistant crops without yield penalties

Application of disease-resistant varieties is the most effective and environmentally friendly way to control crop diseases. However, there is often a trade-off between disease resistance and yield. Several recent studies have demonstrated that genome-editing technology brings a new strategy for generating disease-resistant crops without yield penalties.

Evaluating the impacts of wide row upland cotton (Gossypium hirsutum L.) production in Georgia

AbstractSuccess stories of wide row cotton production have generated producer interest across the cotton belt. The objective of this study was to quantify the effect of row spacing on (1) cotton growth and development and (2) lint yield and fiber quality in Georgia. The cotton cultivar Deltapine DP 1646 (Bollgard 2, XtendFlex; Bayer Crop Science) was planted in 2021 and 2022 in Tifton, GA, at row spacings of 91 cm, 122 cm, 152 cm, and 183 cm. Although canopy closure was delayed in wider row spacings compared to the 91‐cm spacing, all other crop growth and development trends did not differ among row spacings. Similarly, row spacing had no effect on the incidence of boll rot/hard lock. The 91‐cm row spacing yielded 1734 kg lint ha−1. The 183‐cm row spacing reduced yield by 15% compared with the grower's standard row spacing of 91 cm. Fiber quality parameters did not differ among row spacing treatments. Seed costs can be reduced in all wide row systems evaluated for cotton, and the 122 and 152‐cm row spacings had similar yields to the 91‐cm row spacing. However, Georgia growers produce peanuts (Arachis hypogea L.) and corn (Zea mays L.), the most common rotational crops for cotton producers, using a 91‐cm row spacing. Consequently, the simplest transition to wide row production would be the 183‐cm spacing, which incurred yield penalties in the current study. Thus, a 91‐cm row spacing is still the most feasible option for Georgia cotton producers.

Reduced Daily Light Integral at the End of Production Can Delay Tipburn Incidence with a Yield Penalty in Indoor Lettuce Production

Indoor vertical farms that grow lettuce commonly encounter tipburn, which is an environmental disorder caused by calcium (Ca) deficiency during the late head-forming stages of lettuce. Characterized by marginal leaf necrosis of young expanding leaves, tipburn reduces marketable yield because of the appearance of these necrotic lesions. Lowering the daily light integral (DLI) to slow the plant growth rate has been a widely practiced approach to avoid tipburn in lettuce, but it largely reduces the final yield. We assessed the effect of lowering the DLI only during the end of production, which is a critical time because it is when tipburn is typically observed. Lettuce plants of tipburn-sensitive cultivars Klee and Rex were grown under a tipburn-inducing condition in growth chambers. Sixteen days after transplanting, the DLI was varied to 100% (L100), 85% (L85), 70% (L70), or 55% (L55) of the original 17.4 mol⋅m−2⋅d−1 to grow the final 12 d. At harvest, tipburn severity was reduced by lowering the DLI, but the magnitude of reduction was cultivar-specific. For ‘Klee’, the lowest tipburn severity was found at L55 (8% ± 2.1% of leaves), but the severity was similar for all other DLI levels (33% ± 3.5% of leaves). For ‘Rex’, tipburn severity was highest in the control (L100; 14% ± 2.8% of leaves) but similar for all other DLI levels (2% ± 0.9% of leaves). Reducing the end-of-production DLI to 55% resulted in a linear decrease in yield by up to 22% and 26% for ‘Klee’ and ‘Rex’, respectively. When the increase in marketable yields and decrease in the electricity cost were considered, decreasing the end-of-production DLI yielded a profitable contribution only for ‘Klee’ (L55). For moderately tipburn-sensitive ‘Rex’, revenue losses attributable to the yield decrease were too large to justify this approach of end-of-production reduced DLI.

Landscape position and cover crops affects crop yields in a terrace-tiled field

Cover crops (CC) provide soil ecosystem benefits including reduced soil erosion, improved soil health, and nutrient cycling. However, the effect of CCs on rotational commodity crop grain yields and nutrient uptake may vary at different landscape positions and under different soil moisture dynamics. The objectives of this study were to determine the influence of CCs in a terraced field on soil moisture at crop emergence and reproductive stages of corn (Zea mays L) and soybean (Glycine max L. Merr.) development, and evaluate CCmix (wheat (Triticum aestivum L.), radish (Raphanus raphanistrum subsp. Sativus), and turnip (Brassica rapa subsp. Rapa)) and cereal rye (Secale cereale L.) effect on corn and soybean grain yield and plant nutrient concentration, respectively. A randomized complete block design with two treatments including cover crop (CC) and no cover crop (no CC) and three replications was used. In this 4-year study, cereal rye produced 1.0–1.6 Mg ha−1 higher aboveground biomass compared to the CCmix species. Nutrient uptake in the CCmix biomass was greater than cereal rye. Soybean yield following cereal rye termination was not influenced by the CC treatment (P = 0.3229). Dry climatic conditions during the soybean growing period and landscape positions influenced grain yield and nutrient uptake. Average soybean yield at different landscape positions was ranked as shoulder (4.8 Mg ha−1) > backslope (4.4 Mg ha−1) > footslope (3.9 Mg ha−1) > channel (3.6 Mg ha−1). In 2021, corn yield was reduced 29% following the CCmix compared to no CC control, indicating a yield penalty when corn was preceded with the CCmix species. In this study, higher CC biomass production exacerbated soil wetness in a wet year (2021), resulting in uneven corn germination and excess soil water stress on plant growth. Increased soil wetness at channel and footslope positions in 2019 and 2021 reduced corn yield 45–70%. This study suggests that CCs in terraced fields can have a neutral or negative effect on the following commodity crop yield depending on the weather conditions.

Heterotic gains, transgressive segregation and fitness cost of sweetpotato weevil resistance expression in a partial diallel cross of sweetpotato

Heterosis-exploiting breeding schemes are currently under consideration as a means of accelerating genetic gains in sweetpotato (Ipomoea batatas) breeding. This study was aimed at establishing heterotic gains, fitness costs and transgressive segregation associated with sweetpotato weevil (SPW) resistance in a partial diallel cross of sweetpotato. A total of 1896 clones were tested at two sites, for two seasons each in Uganda. Data on weevil severity (WED), weevil incidence (WI), storage root yield (SRY) and dry matter content (DM) were obtained. Best linear unbiased predictors (BLUPs) for each clone across environments were used to estimate heterotic gains and for regression analyses to establish relationships between key traits. In general, low mid-parent heterotic gains were detected with the highest favorable levels recorded for SRY (14.7%) and WED (− 7.9%). About 25% of the crosses exhibited desirable and significant mid-parent heterosis for weevil resistance. Over 16% of the clones displayed superior transgressive segregation, with the highest percentages recorded for SRY (21%) and WED (18%). A yield penalty of 10% was observed to be associated with SPW resistance whereas no decline in DM was detected in relation to the same. Chances of improving sweetpotato through exploiting heterosis in controlled crosses using parents of mostly similar background are somewhat minimal, as revealed by the low heterotic gains. The yield penalty detected due to SPW resistance suggests that a trade-off may be necessary between maximizing yields and developing weevil-resistant cultivars if the current needs for this crop are to be met in weevil-prone areas.

Breeding Novel Rice Hybrids for Aerobic Ecology: A Way Out from Global Warming and Water Crisis

The development of novel rice hybrids is a prospectus area of research for enhancing grain yield to meet the growing population demands. An experiment was conducted in 2016–2017 to develop novel rice hybrids for aerobic ecology with lesser yield penalties than irrigated ecosystems, with the added advantage of reduced methane emissions and water budget as witnessed in irrigated systems. Based on the restorer-maintainer reaction and spikelet fertility (%), ten restorer lines were selected to cross with three CMS (Cytoplasmic male sterile) lines in the Line by Tester fashion in Yasangi (summer) season 2016–2017. They resulted in 30 experimental hybrids besides 13 parental lines (10 restorer lines and 3 B—lines of akin CMS lines) and checks (GK 5022, CR Dhan 201) assessed during the Vankalam (rainy) season 2017 at three different places/locations viz., Rajendranagar, Warangal, and Kampasagar. The outcome of the experiment was that two experimental hybrids viz., APMS-6A × HRSV-7 and IR-79156A × ATR-372, were categorized as stable hybrids with desirable sca (Specific combining ability) effects, heterosis (ranging from 7% to 13%) over best check GK 5022, along with an in-essence performance for yield and other yield attributing characters.

Precision editing of GLR1 confers glufosinate resistance without yield penalty in rice.

Precision editing of GLR1 confers glufosinate resistance without yield penalty in rice.

Selection and application of four QTLs for grain protein content in modern wheat cultivars

The grain protein content (GPC) is the key parameter for wheat grain nutritional quality. This study conducted a resampling GWAS analysis using 406 wheat accessions across eight environments, and identified four previously reported GPC QTLs. An analysis of 87 landraces and 259 modern cultivars revealed the loss of superior GPC haplotypes, especially in Chinese cultivars. These haplotypes were preferentially adopted in different agroecological zones and had broad effects on wheat yield and agronomic traits. Most GPC QTLs did not significantly reduce yield, suggesting that high GPC can be achieved without a yield penalty. The results of this study provide a reference for future GPC breeding in wheat using the four identified QTLs.

Maximizing winter wheat yield through planting date and seeding rate management

AbstractPlanting date and seeding rate are two of the most basic and important factors in determining yield potential in winter wheat (Triticum aestivum L.) due to their impact on stand establishment. Timely planting of winter wheat (within a few days after the Hessian fly free date) ensures sufficient time for fall growth and tillering, which are critical for maximizing yield, while adequate seeding rate is necessary to optimize the number of heads per unit area. Field experiments were conducted in Mason, MI during three growing seasons (2020–2022) utilizing five planting dates, ranging from mid‐September to mid‐November, and five seeding rates ranging from 0.8 to 2.4 million seeds acre−1. There was no interaction between planting date and seeding rate in determining yield. Yields declined by 22–48% from the earliest to the latest planting dates in response to a 33–47% reduction in the number of heads acre−1. Seeding rate did not significantly impact yield except at low seeding rates under delayed planting. Maximum yield was achieved with a seeding rate of 0.93, 1.37, 1.47, 1.54, and 1.85 million seeds acre−1 during the mid‐September, late September, mid‐October, late October, and mid‐November plantings, respectively. Overall, results demonstrated that timely planting of wheat is critical for maximizing yield, with significant yield reductions occurring when planting is delayed, regardless of the seeding rate used. Furthermore, while low seeding rates may be used within the optimal planting window without yield penalty, seeding rates should be progressively increased as planting is delayed to diminish yield loss.

Responses of Physiological Traits and Grain Yield to Short Heat Stress during Different Grain-Filling Stages in Summer Maize

Maize kernel growth is sensitive to heat stress, which is predicted to result in yield loss. However, the response of maize to short-term heat stress during different kernel-growth stages is still not clear. A 3-year field experiment, included two heat-stress treatments (LSH, lag-stage heat stress; FSH, effective-filling-stage heat stress), was conducted in 2019–2021. The results showed that LSH and FSH significantly reduced the grain yield by 8.7–14.9% and 11.6–17.6%, respectively, compared with the control (CK). LSH mainly reduced the kernel number per ear, and FSH mainly reduced the kernel weight. Heat stress reduced the SPAD and chlorophyll content during the effective-filling stage, but not in the lag stage. Photosynthesis was obviously reduced under heat stress during both stages; however, the photosynthesis rate during the lag stage was higher than during the effective-filling stage. The decreased amplitude of dry matter under LSH was higher than under FSH during the heating period. However, there was no difference between the CK and LSH samples in terms of dry-matter accumulation from the end of heat stress to harvest, which was significantly reduced under FSH. Additionally, decreased starch-synthesis-related enzyme activity, i.e., adenosine diphos-phoglucose pyrophosphprylase, contributed to the kernel number and kernel weight loss in LSH and FSH, respectively. The kernel-growth rate (per ear) was lowered, but the growth duration was not shortened in this study. Consequently, LSH mainly reduced the photosynthesis rate (Pn), resulting in kernel abortion and yield penalty. FSH mainly reduced the Pn and chlorophyll content, which reduced the kernel weight, and increased yield loss.

Mid-season adjustment of nitrogen fertilizer for rice with two plant spacings

ContextFertilizer recommendations for rice (Oryza sativa L.) in Asia often split a predetermined amount of N into several applications to match N supply with anticipated crop demand for N. Within-season deviations from anticipated N demand could necessitate mid-season adjustments in N applications to ensure closure of exploitable yield gaps. ObjectiveWe hypothesized that application of additional fertilizer N to satisfy an underestimated crop demand for N could be delayed until two weeks after panicle initiation without a yield penalty. We additionally examined whether effects of mid-season N adjustments on rice differed between two plant spacings with different plant populations. MethodsField experiments with irrigated, transplanted rice were conducted at two sites in two seasons in North Sumatra, Indonesia. The experimental design was a factorial combination of two rice cultivars, two plant spacings, and seven N treatments. ResultsRice growth and yield components sometimes differed between equally spaced rows (square planting) and alternating narrow and wide rows (legowo), but grain yield with legowo consistently matched and sometimes exceeded yield with square planting. Effects of N treatments — with varying rates and split applications of N — on yield were comparable across the two plant spacings and two cultivars. A predetermined fertilizer recommendation with three split applications of N underestimated the N needed for high yield in all experiments. Application of 30 kg ha−1 more N than the recommended 155 kg ha−1 in dry season (DS) and 125 kg ha−1 in wet season (WS) increased yield by up to 0.5 Mg ha−1 in DS and 0.7 Mg ha−1 in WS and consistently increased net income in both seasons. Additional N at tillering in DS increased vegetative biomass but not yield. Additional N in both seasons could be delayed until 12–14 days after panicle initiation for highest yield. ConclusionsOur study represented circumstances where a fertilizer recommendation provided to farmers before a growing season merited an upward mid-season adjustment in N rate to achieve higher yield. The upward mid-season N adjustment of 30 kg ha−1 in our study could be delayed until two weeks after panicle initiation with no yield penalty in both seasons, for both cultivars, and for both equally spaced rows and alternating narrow and wide rows of transplanted rice. ImplicationsFarmers and advisory services using crop and/or weather monitoring to identify fields meriting additional mid-season N can delay the application of additional N until panicle initiation or two weeks after panicle initiation.