Early Sowing Dates Research Articles

Plant growth rate after, and not during, waterlogging better correlates to yield responses in wheat and barley

AbstractWaterlogging is a stress that affects wheat (Triticum aestivum L.) and barley (Hordeum vulgare L. ssp. distichum) yield. This work aimed at analysing the impact of a waterlogging event during pre‐anthesis (critical period) on yield, its numerical components and their relationships with plant growth rate in wheat and barley. Two pot experiments were carried out under contrasting environmental conditions (early and late sowing date), in which six wheat and six barley cultivars were exposed to control and waterlogging conditions imposed c. 18 days prior to anthesis. Measurements included total above‐ground biomass at the beginning and at the end of the waterlogging treatment and at maturity, when grain yield and its numerical components were also measured. Wheat showed higher yield losses (−76%) due to waterlogging than barley (−49%). Grain yield was explained by both numerical components (the number of grains per plant and grain weight), which better correlated with the relative growth rate of plants during the post‐stress recovery than during the waterlogging period. Plant growth during the recovery period should be targeted as a key factor to estimate yield losses from waterlogging in these cereals.

EFFECT OF SOWING DATE AND INTERCROPPING SYSTEM OF SUNFLOWER WITH SUGAR BEET ON THE PRODUCTIVITY OF BOTH CROPS.

A field study was conducted during 2018/2019 and 2019/2020 seasonsinItay EL-Baroud Agric. Res. Station,Beheira Governorate, Egypt, to study the effect of three sowing dates of sunflower (simultaneously with sugar beet (T1), twenty one days after sowing sugar beet (T2) andthirty five days after sowing sugar beet(T3)) and three intercropping systems(25% (S1),33.3% (S2)and 50% (S3)of sunflower plant density + 100% sugar beet)on yield and yield components of both crops.A split plot design with four replications was used. Results showed that all studied characters of sugar beet were significantlyaffected by sowing dates and intercropping systems of sunflower. Intercropping system (S1)significantly increasedall characters of sugar beet at T3over the other treatments. Early sowing date(T1)significantly accelerated days to 50% of flowering and maturity date and recorded the highest values for each of growing degree days (GDD) andseed yield and its componentsof sunflower. Significant differences were recorded for sunflower studied traits as affected by the intercropping systems. The highest seed and oil yields/fad., were achieved with sole sunflower followed byS3system at T1 compared with the other treatments. The highest land equivalent ratio (LER)value 1.46 was recorded at T2 with S3, followed by 1.44 with T2 x S1, as average of both seasons.While T2 x S1 had the highest relative crowding coefficient (RCC) and net return. It can be concluded that T2 x S1 had the highest sugar yield valued 4.74 ton/fad.,increased net return by 28.30% and produced 26.10 ton sugar beet plus 444.63kg seed of sunflower compared to sole sugar beet which had 26.91 ton sugar beet.

Влияние сроков посева моркови на формирование урожая в условиях мерзлотных почв Якутии

In the Nyurbinsky Districtof Yakutia, on permafrost-taiga pale-yellow soil, the experiments were carried out to study the influence of carrot sowing dates on its yieldsand weed infestation. The experimental design included 4 vari-ants with different sowing dates: 1) May 22-25 -control; 2) May 15-18; 3) May 22-25; 4) May 29-31. The carrot sow-ing rate was 4 kg ha; the accounting area of the experi-mental plot was 22.4 m2; there were four replications; the placement of variants was systematic. The research target was the carrot variety Nantskaya released for the Republic of Sakha (Yakutia). The soil of the experimental plot was permafrost-taiga pale-yellow transitional old-arable soil, medium loamy in its particle-size distribution. The experi-ments showedthat early shoots and yield formation result-ed from early spring and under-winter sowing dates (by 6 and 9 days earlier than the control sowing dates, respec-tively); a significant yield gain of root crops as compared to the control variant resulted from the early spring sowing dates (May 15-18) -by 1.27 t ha, or 114% of the yield. The studies allowed concluding that the best sowing dates of carrots in permafrost soils of the cryolithic zone is the early spring period (May 15-18) which ensures the early tech-nical ripeness of root crops (by 9 days earlier than the con-trol), the least weed infestation and high yields (30.2 t ha

Yield and Sowing Qualities of Winter Bread Wheat Seeds Depending on the Preceding Crops and Sowing Dates in the Forest-Steppe of Ukraine

Wheat is one of the most important crops in the world due to its wide geographical adaptation and nutritional value. The use of high-quality seeds of the best varieties being adapted to local growing conditions is an important requirement for increasing wheat yields. The purpose of this research was to establish the influence of preceding crops and sowing dates on yield and seed sowing quality of winter bread wheat varieties. On average, maximum yield capacity in 2016–2018 was obtained in the variety Trudivnytsia myronivska (7.41 t/ha) when sowing on 15 September after green manure, the minimum yield was in the variety MIP Kniazhna (4.03 t/ha) when sowing on 15 October after soybean as preceding crop. Shifting the sowing dates to later ones led to decrease in yield capacity by 0.97 and 0.62 t/ha after the preceding crops green manure and soybean, respectively. After the preceding crop soybean, the maximum yield (5.77 t/ha) was formed by the variety MIP Valensiia when sowing on 25 September. By ANOVA it was found that the level of wheat yield was the most significantly affected by hydrothermal conditions of the year (63%), the interaction “preceding crop  conditions of the year” (12%) and preceding crop (11%). It was revealed that an increase in weight of 1000 seeds in the varieties on average was 3.9 g after the preceding crop green manure in comparison with the preceding crop soybean. There was a slight effect of preceding crops and sowing dates on seed vigor and laboratory germination. These rates were slightly higher for early and optimal sowing dates after green manure as compared with the soybean. Thus, it was confirmed that in the Right-Bank Forest-Steppe green manure is the best preceding crop for seed production, especially for growing pre-basic seeds, while 15 and 25 September are the best sowing dates. For the preceding crop soybean, when sowing on 25 September and 05 October, the yield of wheat varieties was the highest in comparison with sowing on 15 October. Locations of winter wheat seed crops after the best preceding crops in crop rotation and optimal sowing dates will promote the most efficient using of climatic and anthropogenic factors, increase grain yield per area unit, and improve seed sowing quality.

Adjusting the sowing date of spring maize did not mitigate against heat stress in the North China Plain

Heat stress due to increases in temperature reduces grain number and yield of spring maize in the North China Plain (NCP). To mitigate heat stress, previous research recommended that postponing the sowing date of spring maize to late May in the NCP. However, other field experiment indicated that early sowing could achieve high grain yield. To resolve the discrepancy in previous studies, a two-year sowing date experiment was conducted from 4 April to 13 June with 14-day interval without drought stress. It was found that high grain yields were obtained in early sowing dates (early and mid- April) in both years. The grain yield and kernel number had no significant relationships with the heat stress in the crucial period bracketing silking, when kernel number is determined (15 days pre- and post- silking). Moreover, the historical meteorological data elucidated that high temperature continued from mid-June to early-August, which contained the silking window of different sowing dates. Additionally, the heat stress risk around silking (>33°C) for different sowing dates was high throughout the past 30 years (>23%), except for 13 June (7%). Moreover, the simulated yields under full irrigation also indicated that adjusting the sowing date to late May did not increase grain yield. We concluded that adjusting sowing date did not mitigate the heat stress around silking, and other factors, such as drought, overcast and rainy stress, influenced the grain number and yield of spring maize in the NCP.

Milk thistle (Silybum marianum L. Gaertn.) achene yield had a positive response to nitrogen fertilization, row spacing, sowing date, and weed control methods

Knowledge of the response of milk thistle to different levels of agronomic inputs and interactions is essential for the elaboration of the best production technologies. Field trials in a fractional factorial design are helpful in selecting the optimal production technology for plants whose agronomic requirements have not been sufficiently studied under given agroecological conditions. The experiment was set up in a 2n-1 design with a half-replication. It was located on fields of the Agricultural Experiment Station in Bałcyny, Poland, and carried out in the years 2010-2012. The multifactorial experiments conducted under the same climatic and soil conditions helped to determine the optimal intensity of the main agronomic treatments.The experiment was designed to analyze the response of milk thistle to key yield-forming factors (nitrogen fertilization, potassium fertilization, sowing date, row spacing and weed control). The weather conditions during the experiment had a significant impact on most of the assessed parameters. Under the agroecological conditions of north-eastern Poland, a higher nitrogen fertilization dose (80 kg N ha-1) had a significant influence on the yield of milk thistle achenes (an increase of 7.1%), and the yield components improved significantly. An earlier sowing date also resulted in a higher yield of achenes (by 14.9%) and improved the yield structure elements. A positive influence on the yield was also produced by chemical weed control (a significant increase in the yield by 0.15 Mg ha-1 – 12.2%). The spacing between rows and potassium fertilization (100 kg K2O ha-1) applied in milk thistle cultivation did not significantly affect the growth, development plant yield.

The Study of temperature depression and its association with grain yield in six wheat cultivars under heat stress conditions and salicylic acid application

In order to evaluate canopy and organs temperature depression (TD) under heat stress conditions and the effects of plant morphology on organs temperature depression and their association with grain yield, two field experiments were conducted using six wheat cultivars (Behrang, Chamran, Kauz, Koohdasht, Karim and Montana) planted on three dates (early, optimum, late) in 2014-2015 and 2015 -2016 cropping seasons in Dashtestan, Bushehr, Iran. In addition, three concentrations of salicylic acid (0, 0.5 and 1 mM) were applied to alleviate the effects of heat stress. Canopy and organs (flag leaf, peduncle and spike) temperature were measured by a hand-held infra-red thermometer (IRT). Also, some morphological traits in addition to yield components were measured. Results showed that the effects of cultivars and heat conditions were significant for most of the studied traits but salicylic acid application showed no significant effects. Under late sowing date, canopy and organs temperature depression were significantly higher than those at early and optimum sowing dates. No significant differences were found between early and optimum sowing dates for all temperature depressions. Among cultivars, Behrang had higher canopy temperature reduction (CTD), flag leaf temperature depression (FLTD) and peduncle temperature depression (PTD). Spike temperature depression (STD) was higher in Chamran and Kauz cultivars. Among plant organs, peduncle had higher temperature depression followed by flag leaf and spike. Canopy and organs temperature depression had positive correlation with stomatal conductance and grain yield. This research suggests that temperature depression can be used as an important criterion for the selection of stable genotypes under late sowing conditions. This is very helpful to improve wheat productivity under terminal heat stress resulting from late sowing conditions.

Genotype and cytokinin effects on soybean yield and biological nitrogen fixation across soil temperatures

AbstractHigh nitrogen (N) supply is required for high‐yielding soybean, but low soil temperatures in either early production systems or cool environments delay nodulation and limit biological nitrogen fixation (BNF). Because cytokinins are key signalling hormones in mediating nodule formation and our initial controlled environment experiment indicated that seed cytokinin treatment increased early BNF and total nodule area, it was used in field trials. Cytokinin was applied (seed or foliar) to two commercial soybean genotypes (DM50I17 and DM40R16) in field trials with early (September and early November) and conventional (late November) sowing dates in Argentina. In the field, DMR50I7 achieved consistent yields across sowing dates because increased BNF compensated for limited soil N uptake in early sowing dates, also leading to 25% higher nitrogen use efficiency (NUE). Surprisingly, soil N uptake was more cold‐sensitive than BNF with greater and prolonged N fixation in early sowing, perhaps through delayed nodulation, leading to improved N harvest index. Cytokinin seed treatment increased BNF (26%) in DM40R16 especially in early sowing dates. Although cytokinin improved cold tolerance of BNF, this was not explained by altered nodulation and did not increase yield. Here we show genetic differences in N supply in commercial soybean genotypes and the importance of BNF to maintain yield in early sown soybean.

Combining Experimental and Modeling Approaches to Understand Genotype x Sowing Date x Environment Interaction Effects on Emergence Rates and Grain Yield of Soybean.

Soybean emergence and yield may be affected by many factors. A better understanding of the cultivar x sowing date x environment interactions could shed light into the competitiveness of soybean with other crops, notably, to help manage major biotic and abiotic factors that limit soybean production. We conducted a 2-year field experiments to measure emergence dynamics and final rates of three soybean cultivars from different maturity groups, with early and conventional sowing dates and across three locations. We also measured germination parameter values of the three soybean cultivars from different maturity groups under controlled experiments to parametrize the SIMPLE crop emergence model. This allowed us to assess the prediction quality of the model for emergence rates and to perform simulations. Final emergence rates under field conditions ranged from 62% to 92% and from 51% to 94% for early and conventional sowing, respectively. The model finely predicted emergence courses and final rates (root mean square error of prediction (RMSEP), efficiency (EF), and mean deviation (MD) ranging between 2% to 18%, 0.46% to 0.99%, and −10% to 15%, respectively) across a wide range of the sowing conditions tested. Differences in the final emergence rates were found, not only among cultivars but also among locations for the same cultivar, although no clear trend or consistent ranking was found in this regard. Modeling suggests that seedling mortality rates were dependent on the soil type with up to 35% and 14% of mortality in the silty loam soil, due to a soil surface crust and soil aggregates, respectively. Non-germination was the least important cause of seedling mortality in all soil types (up to 3% of emergence losses), while no seedling mortality due to drought was observed. The average grain yield ranged from 3.1 to 4.0 t ha−1, and it was significantly affected by the irrigation regime (p < 0.001) and year (p < 0.001) but not by locations, sowing date or cultivars. We conclude that early sowing is unlikely to affect soybean emergence in South-West of France and therefore may represent an important agronomic lever to escape summer drought that markedly limit soybean yield in this region.

Evaluating the integrative response of moringa leaf extract with synthetic growth promoting substances in maize under early spring conditions

The performance of spring maize is severely hampered by high temperature at reproductive phase, causing marked reduction in grain yield. Early sowing of spring maize can be a good adaptive approach however, due to low temperature causes adverse effect on germinating seeds and young seedlings, thus being detrimental to early planting. Exogenous application of natural and synthetic growth promoting substances may induce tolerance against temperature constraints. For this purpose, field experiment was conducted to explore the potential of moringa leaf extract (MLE, 3%), sorghum water extract (SWE, 10 ml L − 1), ascorbic acid (ASA, 50 mg L − 1), salicylic acid (SA, 50 mg L − 1) and hydrogen peroxide (H2O2, 2 µM) as priming agents on maize hybrid under early and optimum sowing dates. The performance of early planted maize crop was severely influenced by low temperature in comparison to optimum sown crop nevertheless exogenous application of growth promoting substances proved effective in improving stand establishment, phenotypic behavior, key physiological and biochemical attributes of maize crop. Low temperature persuaded inhibition in growth of maize was mainly ameliorated by seed priming with MLE + H2O2 and SWE + ASA. It can be concluded that application of growth promoting substances as priming agents proved to be the most successful strategy in conferring better thermotolerance at early sowing through improved antioxidant defense system and physiological mechanism of spring maize. Better crop performance with combined application of natural and synthetic growth enhancers was linked to improvement in crop stand establishment, better growth and development, dry matter partitioning and yield attributes.

Rules for grown soybean-maize cropping system in Midwestern Brazil: Food production and economic profits

Soybean-maize cropping system is highly dependent on climate condition, especially water deficit, across Brazil, affecting yield, food production and farmers profit. Based on that, the aim of this study was to evaluate the food production and economic viability for soybean and maize for single and soybean-maize off-season production system considering sowing dates, soil types and yield gaps in the Midwestern region. The yield was simulated using FAO-Zone agroecological model. Official yield statistics were used to validate the crop model and to estimate yield gap. We consider single soybean (SSc), single maize (SMc), and soybean-maize off-season systems (SMcs), simulating yield for 35 growing seasons (1981–2015) and six sowing dates (Oct. 01–Dec. 15 for single soybean and single maize; and Jan. 09–Mar. 26 for maize off-season, after soybean harvest). Total production was obtained in function of yield, yield gap, soil type and production intensity. Farmers profit was obtained based on net revenue using independent random function (5000 interactions) for yield, sales price and production costs. The SSc had the largest scenarios with positive net revenue, while SMcs had higher net revenue, reaching R$ 7400.00 ha−1, but with lowest risk for early sowing dates (soybean sowed in Oct. 01 and Oct. 15, and maize off-season in Jan. 09 and Jan. 24). The SMc had higher risk and lower food production in the region. The maximum gross energy production was 2663 billion MJ in SMcs sown soybean on Oct. 01. The SSc had a stable production of gross energy across the sowing dates, with values around 1900 billion MJ. The production of crude protein was similar among SMcs and SSc across sowing dates. The higher crude protein production occurred in the sowing date Oct. 15 for SMcs, with 33.9 billion kg, while SSc produced 32.9 billion kg. The highest net revenue was obtained for the SMcs in the early sowing dates. Nevertheless, the SMcs produced the highest amount of gross energy than single crop systems, but with a very similar crude protein level than SSc. Thus, farmers can be encouraged to grow SMcs to improve food production in early sowing dates. However, public incentive policies through insurance against water deficit can guarantee minimal economic returns and reduce production risks for maize off-season, especially when soybean was sowing late by delay at beginning of rain.

Millet forage yield and silage quality as affected by water and nitrogen application at different sowing dates

AbstractThis experiment was conducted to evaluate the effects of two irrigation regimes (control and water stress) and two nitrogen (N) levels (0 and 112.5 kg/ha) on forage yield and silage quality in millet. Bastan (Setaria italica (L.) P. Beauv) and Pishahang (Panicum miliaceum) were sown at two different dates during 2015 and 2016. Both cultivars exhibited reduced dry‐matter (DM) yields (45% and 51% in Bastan and Pishahang respectively) due to drought stress. Proline and phenolic contents increased as a result of drought and were significantly and negatively correlated with DM yield and digestibility. Moreover, Pishahang had a reduced acid detergent fibre (ADF) content but improved leaf/stem ratio, digestible dry matter (DDM), relative feed value (RFV), net energy for lactation (NEL), digestibility and silage quality as a result of drought stress, while no significant effects on these traits were observed in Bastan. Silage quality was greatly cultivar‐dependent. Both cultivars had higher levels of DDM, RFV and NEL at early sowing dates. Nitrogen supply had greater positive effects on increasing ash, crude protein (CP) content and DM yield under normal irrigation than under water‐stress conditions. In summary, given the importance of the energy received per unit of forage from an animal husbandry viewpoint and the significance of DM yield per unit area from an agricultural viewpoint, the obtained results might help farmers in choosing not only the best sowing dates but also proper irrigation and N management practices to achieve their quantitative and qualitative objectives in forage production.

Uticaj organskog i konvencionalnog sistema gajenja i datuma setve na prinos semena i sadržaj ulja i proteina u sortama uljane repice

Rapeseed is one of the major oil crops, grown in various agroecological conditions. Interest in organic rapeseed is rising, with increasing importance to breeders to determine the need for specific organic breeding programs. The objective of this study was to determine the adaptive value of rapeseed cultivars in organic farming environments. Five winter rapeseed cultivars were grown in conventional and organic plots, each with three sowing dates in four replications. The trials were organized using a randomized block design. The effect of cultivar and farming on emergence, percentage of harvested plants, yield, oil and protein content were investigated. Locally recommended agricultural practices were used to keep the fields free from weeds, insects and diseases. In organic field, weeds were removed mechanically while insects were treated using organic insecticide. The seed samples for analysis of oil and protein content were taken during harvest. Considering agricultural practices, it was found that rapeseed can be successfully grown in organic agriculture, but further improvements are needed to increase stability of production. Early sowing date provides enough time for rapeseed growth before the winter and good overwintering. The cultivars had higher oil content in the conventional farming, while there was no significant effect of farming system on protein content. For cultivar Slavica, higher yield was recorded in organic system, while cultivars Banacanka and Nena had high yield in both farming systems. The results suggest that the existing conventional breeding material can be used as a good starting point for further trait improvements in organic farming.

Analysis of soybean germination, emergence, and prediction of a possible northward establishment of the crop under climate change

Abstract Soybean (Glycine max (L.) Merr.) has the potential to improve sustainability of agricultural production systems. A higher focus on this crop is needed to re-launch its production in the EU. A better understanding of key determinants affecting soybean establishment represents a first step to facilitate its adoption in cropping systems. To this objective, we conducted laboratory and field experiments in order to better characterize seed germination and seedling growth in relation to temperatures, water content, and soil structure. We then used these data to parametrize the SIMPLE crop emergence model and to evaluate its prediction quality, by comparing observed field germination and emergence data with the predicted ones. Finally, we performed a simulation study over the 2020–2100 period, for three sowing dates, from mid-March to mid-April, in the northern climate of France to evaluate whether soybean will successfully establish in the Northern part of the country under future climate change. Experimental results showed that soybean germination was very fast, taking only 17 °C days to reach 50% germination at optimal conditions. The base, optimum and maximum temperatures were determined as 4, 30 and 40 °C, respectively while the base water potential was −0.67 MPa, indicating a high sensitivity to water stress. The SIMPLE model finely predicted germination and emergence courses and their final rates, compared with the observed field data. The simulation study showed average emergence rate ranging from 61 to 78% with little variability among sowing dates and periods, but a high variability between years. Main causes of non-emergence were: i) seedling mortality due to clods or soil surface crust, followed by ii) non-germination, and iii) seedling mortality due to drought. When sown in mid-April, seedling mortality due to drought was higher compared with earlier sowing dates. These results provide a better knowledge of soybean establishment that are encouraging to introduce soybean with early sowings to diversify current cropping systems.

ОПТИМІЗАЦІЯ КОНВЕЄРНОГО ВИРОБНИЦТВА ЗЕЛЕНИХ КОРМІВ

It was established that the use of the pasture complex from seeded bean- cereals and natural herbs, combined with the formation of mixtures of annual crops of early sowing dates with the participation of spring vetch, oat seed, spring rapeseed and radish oil and multiconious use of rare high-yielding phytocenoses of sylphia periannolystic, Jerusalem artichoke and garden burnet polygamous provides a stable conveyor production of cheap and high-grade grassy feed, it allows to optimize the necessary set of crops and increase the resource potential of the territory.

Performance of Chia on Different Sowing Dates: Characteristics of Growth Rate, Leaf Area Index, Shoot Dry Matter Partitioning and Grain Yield

The objective of this study was to comparatively determine the characteristics of growth rate, leaf area index, shoot dry mass partitioning and grain yield of chia plants (Salvia hispanica L.) on different sowing dates. A field experiment was conducted in the crop year of 2016/2017 in five sowing dates (09/22/16, 10/28/16, 01/03/17, 02/08/17 and 03/24/17) with a randomized complete block design and four replicates. Plant growth was determined through field samplings to determine the dry matter mass and leaf area performed every 15 days. The following physiological indexes were calculated: relative growth rate, absolute growth rate, net assimilation rate, leaf area ratio, specific leaf area and leaf mass ratio. To weekly evaluate plant height, ten plants per plot were marked after emergence, and the final height was considered when plants reached physiological maturity. A useful area of 2.10 m&amp;sup2; per plot was collected for evaluating grain yield. The physiological indexes indicated that at earlier sowing dates there is a greater plant growth, either in shoot dry matter mass, height and leaf area index. The leaf area index of branches is progressively increased with plant development and contributes significantly to total leaf area index of chia plants in all studied sowing dates. The main stem represents between 60 and 70% of the shoot dry matter accumulated in the early sowing dates, and between 40 and 50% in late sowing. The best sowing date in terms of grain yield is 01/03/17.

Effect of Sowing Date and Harvest Schedule on Organic Spinach Grown during the Winter in High Tunnels

In a two-part study, we examined the effect of sowing date and harvest schedule on the yield of spinach (Spinacia oleracea) grown during the winter in 16 × 32-ft-high tunnels in northern New Mexico. Each part of the study was conducted for two growing seasons and took place between 2012 and 2015. In Study A (2012–13 and 2013–14), spinach was sown four times at roughly 2-week intervals (mid-October, early November, mid-November, and early December) and plant density (plants per square foot), plant height (centimeters), and yield (grams per square foot) were measured for three harvests in mid-January, mid-February, and mid-March. The earliest sowing date had the least-dense stands, and plant density increased with each subsequent sowing. The two earliest sowing dates had significantly higher season-long yield than the later two sowings. In Study B (2013–14 and 2014–15), all plots were sown in mid-October, but harvest schedule treatments were staggered such that harvests began at 9, 11, 13, or 15 weeks after sowing and continued at irregular intervals. Treatment 2, with harvests beginning after 11 weeks, had the greatest season-long yield, slightly greater than when harvests began at 9 weeks, and significantly more than when harvest began 13 weeks or later. More importantly, a staggered harvest schedule can provide spinach weekly for direct marketing opportunities.

A New Integrated Vegetation Index for the Estimation of Winter Wheat Leaf Chlorophyll Content

Leaf chlorophyll content (LCC) provides valuable information about the nutrition and photosynthesis statuses of crops. Vegetation index-based methods have been widely used in crop management studies for the non-destructive estimation of LCC using remote sensing technology. However, many published vegetation indices are sensitive to crop canopy structure, especially the leaf area index (LAI), when crop canopy spectra are used. Herein, to address this issue, we propose four new spectral indices (The red-edge-chlorophyll absorption index (RECAI), the red-edge-chlorophyll absorption index/optimized soil-adjusted vegetation index (RECAI/OSAVI), the red-edge-chlorophyll absorption index/ the triangular vegetation index (RECAI/TVI), and the red-edge-chlorophyll absorption index/the modified triangular vegetation index(RECAI/MTVI2)) and evaluate their performance for LCC retrieval by comparing their results with those of eight published spectral indices that are commonly used to estimate LCC. A total of 456 winter wheat canopy spectral data corresponding to physiological parameters in a wide range of species, growth stages, stress treatments, and growing seasons were collected. Five regression models (linear, power, exponential, polynomial, and logarithmic) were built to estimate LCC in this study. The results indicated that the newly proposed integrated RECAI/TVI exhibited the highest LCC predictive accuracy among all indices, where R2 values increased by more than 13.09% and RMSE values reduced by more than 6.22%. While this index exhibited the best association with LCC (0.708** ≤ r ≤ 0.819**) among all indices, RECAI/TVI exhibited no significant relationship with LAI (0.029 ≤ r ≤ 0.167), making it largely insensitive to LAI changes. In terms of the effects of different field management measures, the LCC predictive accuracy by RECAI/TVI can be influenced by erective winter wheat varieties, low N fertilizer application density, no water application, and early sowing dates. In general, the newly developed integrated RECAI/TVI was sensitive to winter wheat LCC with a reduction in the influence of LAI. This index has strong potential for monitoring winter wheat nitrogen status and precision nitrogen management. However, further studies are required to test this index with more diverse datasets and different crops.

Effects of climate change and adaptation options on winter wheat yield under rainfed Mediterranean conditions in southern Portugal

Projected warming and drying trends over the Mediterranean region represent a substantial threat for wheat production. The present study assesses winter wheat yield response to potential climate change and estimates the quantitative effectiveness of using early flowering cultivars and early sowing dates as adaptation options for the major wheat production region of Portugal. A crop model (STICS) is used for this purpose, which is calibrated for yield simulations before projecting future yields. Climate projections over 2021–2050 and 2051–2080 under two emission scenarios (RCP4.5 and RCP8.5) are retrieved from bias-adjusted datasets, generated by a ten-member climate model ensemble. Projected intensification of water deficits and more frequent high-temperature events during late spring (April–June), coinciding with the sensitive grain filling stage, primarily result in continuous mean yield losses (relative to 1981–2010) by − 14% (both scenarios) during 2021–2050 and by − 17% (RCP4.5) or − 27% (RCP8.5) during 2051–2080, also accompanied by increased yield variabilities. Of evaluated adaptation options at various levels, using earlier flowering cultivars reveals higher yield gains (26–38%) than that of early sowings (6–10%), which are able to reverse the yield reductions. The adopted early flowering cultivars successfully advance the anthesis onset and grain filling period, which reduces or avoids the risks of exposure to enhanced drought and heat stresses in late spring. In contrast, winter warming during early sowing window could affect vernalization fulfillment by slowing effective chilling accumulation, thus increasing the pre-anthesis growth length with limited effects on advancing reproductive stage. Crop yield projections and explored adaptation options are essential to assess food security prospects (availability and stability) of dry Mediterranean areas, providing crucial insights for appropriate policymaking.

Determination of optimal sowing dates and densities of winter wheat under Quebec growing conditions

The objective of this project was to determine the optimal sowing dates and densities for winter wheat to increase winter survival and yield under Quebec growing conditions. The trials were carried out from 2014 to 2016 at four sites, representing three cereal production zones (zones 1, 2, and 3). Three cultivars were assessed using four sowing dates and four seeding densities (250, 350, 450, and 550 seeds m−2). In the first year, the wheat at two of the four sites survived (82%–100%), and in the second year, all the sites showed good survival rates (69%–99%). In zone 2, winter survival was higher for the early sowing dates compared with later dates. Sowing date and seeding density had no effect on survival in zones 1 and 3. Maximum yields were attained with sowing dates from mid- to late September in zone 1; from early to mid-September in zone 2; and from mid-August to mid-September in zone 3. An increase in seeding density from 250 to 550 seeds m−2led to an average yield gain of 9% in zones 2 and 3, but no gain in zone 1. Winter survival rates and yield differ between cultivars.