Early Tillering Research Articles

Effect of Irrigation and Nitrogen Application at Early Tillering, Panicle Initiation and Flowering Stages on the Yield and Yield Attributes of Boro Rice

The study aimed to evaluate the impact of irrigation scheduling and nitrogen splitting on the yield and yield attributes of boro rice, with particular emphasis on critical growth stages including early tillering, panicle initiation and flowering stages. The experiment was executed at the Agronomy Field Laboratory of the Department of Agronomy and Agricultural Extension, University of Rajshahi, from December 2022 to May 2023. The experiment setup was demonstrated using a split plot design, incorporating three replications. Two factors were determined for the experiment: the first included three different watering schedules aiming critical growth stages: early tillering (I1), early tillering and flowering (I2), and early tillering, panicle initiation and flowering panicle initiation (I3). The second factor was distinct nitrogen splitting techniques, which consisted of four levels: control (N0), 138 kg N ha-1 as basal (N1), 69 kg N ha-1 at early tillering and flowering stages (N2), and 46 kg N ha-1 at early tillering, panicle initiation and flowering stages (N3). The highest reading of chlorophyll content was noticed in I3 along with productive tillers (15.67), grains (115.25) and yield outcome (4.44 t ha-1). Regarding nitrogen application, the greatest chlorophyll content, number of functional tillers (13.32), productive grains (112.44) panicle-1 and grain yield (4.48 t ha-1) was recorded in treatment N3. Therefore, the research finding suggest that the application of water at early tillering, panicle initiation and flowering stages along with the application of 46 kg N ha-1 will be helpful to maximize the production of rice in drought prone areas. This approach not only maximizes yield but also helps to mitigate water wastages associated with excessive irrigation.

Impact of nitrogen and potassium management on growth, nutrient uptake and nutrient use efficiency of rice under semi dry condition

The current study was aimed to search effect of nitrogen doses and time of application on performance of semi dry rice. The field experiment was conducted at College of Agriculture,(V. C. Farm), Mandya, University of Agricultural Sciences, Bengaluru during kharif 2019 and 2020, which comes under Southern Dry Zone of Karnataka (Zone-VI) to study the response of semi dry rice on growth and nutrient use efficiency under two doses of nitrogen and potassium doses (100% RDNK, 125%RDNK) as main treatments and seven time of application as sub treatments.The result revealed that higher SPAD meter reading (37.77) and nutrient uptake (77.90, 27.98 and 24.14 kg ha-1)was seen in 125% RDNK and higher nitrogen and potassium use efficiency was observed in 100%RDNK (49.30, and 98.59 kg kg-1 nutrient applied respectively). Where as in split application, higher SPAD meter reading (38.90), nutrient uptake (81.82, 29.57 and 25.35kg ha-1)and nutrient use efficiency (49.86, 11.33 and 99.73 kg kg-1 nutrient applied respectively) was recorded in N at 4 splits as, 25% each at sowing, early tillering, tillering and panicle initiation, K at 2 splits (50% at basal and 50% at panicle initiation) compared to rest of the application. Hence application of application of 125% RDNK, N at 4 splits as, 25% each at sowing, early tillering, tillering and panicle initiation, K at 2 splits (50% at basal and 50% at panicle initiation) is the appropriate time for rice production Southern Dry Zone of Karnataka.

Spectral-based estimation of chlorophyll content and determination of background interference mechanisms in low-coverage rice

The chlorophyll content is a vital indicator of rice growth and nutritional status. However, estimating the rice chlorophyll content using spectral-based techniques at the early tillering stage is challenging because of background interference. Using the energy conservation principle, this study explained the spectral variation and background interference mechanisms of clear, muddy, and green algae-covered backgrounds. We developed mathematical interference models for the three types of backgrounds and determined their interference degree and influence mode. We developed rice chlorophyll content estimation models for unclassified and classified (clear, muddy, and green algae-covered) backgrounds using 12 preprocessing, four wavelength selection, and three modeling methods, and we explored the importance of background classification. Moreover, we found that the optimal chlorophyll content estimation model for the clear background was SS+UVE+CNN, with R2 and RMSE values of 0.786 and 13.191 in the training set and 0.741 and 15.327 in the test set, respectively; that for the muddy background was MSC+GA+CNN, with R2 and RMSE values of 0.914 and 10.425 in the training set and 0.660 and 16.844 in the test set, respectively; and that for the green algae-covered background was DC+GA+CNN, with R2 and RMSE values of 0.904 and 9.111 in the training set and 0.688 and 17.694 in the test set, respectively. Our study could provide valuable insights into reducing and correcting background interference during proximal remote sensing data collection.

Alternating wet and dry irrigation cycles enhance the nitrogen “cache” function of duckweed in a rice-duckweed system

In continuously-flooded paddies, the small, fast-growing aquatic plant duckweed (Lemna minor L.) considered to compete with rice for nitrogen, thereby having a negative impact on early rice growth. While duckweed overpopulation was known can be effectively overcome through field water management, the influence of such management on the N fate and its use efficiency in rice-duckweed systems is poorly documented. Accordingly, a three-year (2020–2022) field experiment was conducted to examine the combined impact on rice yield, as well as N loss and utilization, of two water management approaches (flood irrigation, FI vs. alternate wetting and drying irrigation, AWD), factorially combined with two rice production systems (rice-duckweed, +D, vs. duckweed-free rice, -D). In AWD+D fields, the density of duckweed generally remained below 250 g m−2 (about 85 % coverage), whereas in FI+D fields it reached 100 % coverage (300 g m−2) within 5 days after transplanting, with individual duckweeds overlapping one another. Following AWD irrigation, duckweed performed as a nitrogen “cache,” akin to a split fertilizer application, with the first of several splits occurring at the rice crop's early tillering stage. Within the first 2 days of a specific wet-dry cycle, duckweed can store 0.5–1.5 g N m−2, and then, within a further 3 days, release 0.3–1.0 g N m−2. In contrast, in FI+D paddies, this caching function occurred once under mid-season drainage, with further N being stored in the duckweeds during the remaining rice production season. As a result, at harvest the 0–0.10 m soil layer's N level increased significantly (p<0.05) in both FI+D (8.5–16.8 %) and AWD+D (14.9–20.8 %) compared to FI-D and AWD-D, respectively. Due to the coverage and storage-release function of duckweed, apparent N loss decreased in rice-duckweed system by 1.4–12.5 % in the FI field and 22.1–31.3 % in the AWD field compared to their respective duckweed-free systems. In FI fields, except for a 10 % relative reduction in nitrogen recovery efficiency (NRE) in 2020, duckweed didn't significantly affect rice yield or NRE. The yield reduction (3.5–6.7 %) and the NRE increase (0.8–7.4 %) under AWD-D (vs. FI-D) was, in the presence of duckweed, compensated for and overrun, resulting in a greater yield (5.3–6.7 %) and NRE (5.4–28.9 %) in the AWD+D vs. AWD-D field. When duckweed was present, AWD irrigation improved the by-path nitrogen cycling through duckweed, making the AWD+D system more beneficial for rice cultivation and the agroecosystem's environment health. The AWD+D system offers a promising measure for building an efficient and sustainable rice-duckweed agroecosystem.

Temporary growth cessation of wheat roots following defoliation

Background and aimsDefoliation triggers the remobilisation of root reserves to generate new leaves which can affect root growth until the shoot resumes net assimilation. However, the duration of root growth cessation and its impact on resource uptake potential is uncertain.MethodsWinter wheat was established in a 4 m high outdoor rhizobox facility equipped with imaging panels, sensors, and access points for tracer-labelling. The wheat was defoliated in autumn at early tillering and roots were imaged at a high-time resolution and analyzed by deep learning segmentation. The water and nitrogen (N) uptake were measured using time-domain reflectometer (TDR) sensors and 2H and 15N isotopes.ResultsRoot penetration of wheat paused for 269 °C days (20 days) following defoliation after which it resumed at a similar rate to un-defoliated plants (1.8 mm °C days−1). This caused a substantial decrease in root density with an associated reduction in water and N uptake at maturity, especially from deeper soil layers (>2 m).ConclusionsOur results have significant implications for managing the grazing of dual-purpose crops to balance the interplay between canopy removal and the capacity of deep roots to provide water and N for yield recovery.

Strigolactone and abscisic acid synthesis and signaling pathways are enhanced in the wheat oligo-tillering mutant ot1

Tiller number greatly contributes to grain yield in wheat. Using ethylmethanesulfonate mutagenesis, we previously discovered the oligo-tillering mutant ot1. The tiller number was significantly lower in ot1 than in the corresponding wild type from the early tillering stage until the heading stage. Compared to the wild type, the thousand-grain weight and grain length were increased by 15.41% and 31.44%, respectively, whereas the plant height and spike length were decreased by 26.13% and 37.25%, respectively. Transcriptomic analysis was conducted at the regreening and jointing stages to identify differential expressed genes (DEGs). Functional enrichment analysis with the Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) databases showed differential expression of genes associated with ADP binding, transmembrane transport, and transcriptional regulation during tiller development. Differences in tiller number in ot1 led to the upregulation of genes in the strigolactone (SL) and abscisic acid (ABA) pathways. Specifically, the SL biosynthesis genes DWARF (D27), D17, D10, and MORE AXILLARY GROWTH 1 (MAX1) were upregulated by 3.37- to 8.23-fold; the SL signal transduction genes D14 and D53 were upregulated by 1.81- and 1.32-fold, respectively; the ABA biosynthesis genes 9-CIS-EPOXICAROTENOID DIOXIGENASE 3 (NCED3) and NCED5 were upregulated by 1.66- and 3.4-fold, respectively; and SNF1-REGULATED PROTEIN KINASE2 (SnRK2) and PROTEIN PHOSPHATASE 2C (PP2C) genes were upregulated by 1.30- to 4.79-fold. This suggested that the tiller number reduction in ot1 was due to alterations in plant hormone pathways. Genes known to promote tillering growth were upregulated, whereas those known to inhibit tillering growth were downregulated. For example, PIN-FORMED 9 (PIN9), which promotes tiller development, was upregulated by 8.23-fold in ot1; Ideal Plant Architecture 1 (IPA1), which inhibits tiller development, was downregulated by 1.74-fold. There were no significant differences in the expression levels of TILLER NUMBER 1 (TN1) or TEOSINTE BRANCHED 1 (TB1), indicating that the tiller reduction in ot1 was not controlled by known genes. Our findings provide valuable data for subsequent research into the genetic bases and regulatory mechanisms of wheat tillering.

The QTL and Candidate Genes Regulating the Early Tillering Vigor Traits of Late-Season Rice in Double-Cropping Systems.

Rice effective panicle is a major trait for grain yield and is affected by both the genetic tiller numbers and the early tillering vigor (ETV) traits to survive environmental adversities. The mechanism behind tiller bud formation has been well described, while the genes and the molecular mechanism underlying rice-regulating ETV traits are unclear. In this study, the candidate genes in regulating ETV traits have been sought by quantitative trait locus (QTL) mapping and bulk-segregation analysis by resequencing method (BSA-seq) conjoint analysis using rice backcross inbred line (BIL) populations, which were cultivated as late-season rice of double-cropping rice systems. By QTL mapping, seven QTLs were detected on chromosomes 1, 3, 4, and 9, with the logarithm of the odds (LOD) values ranging from 3.52 to 7.57 and explained 3.23% to 12.98% of the observed phenotypic variance. By BSA-seq analysis, seven QTLs on chromosomes 1, 2, 4, 5, 7, and 9 were identified using single-nucleotide polymorphism (SNP) and insertions/deletions (InDel) index algorithm and Euclidean distance (ED) algorithm. The overlapping QTL resulting from QTL mapping and BSA-seq analysis was shown in a 1.39 Mb interval on chromosome 4. In the overlap interval, six genes, including the functional unknown genes Os04g0455650, Os04g0470901, Os04g0500600, and ethylene-insensitive 3 (Os04g0456900), sialyltransferase family domain containing protein (Os04g0506800), and ATOZI1 (Os04g0497300), showed the differential expression between ETV rice lines and late tillering vigor (LTV) rice lines and have a missense base mutation in the genomic DNA sequences of the parents. We speculate that the six genes are the candidate genes regulating the ETV trait in rice, which provides a research basis for revealing the molecular mechanism behind the ETV traits in rice.

Design and Development of Rice Pot-Seedling Transplanting Machinery Based on a Non-Circular Gear Mechanism

Transplanting rice pot seedlings without damaging the roots, which promotes early tillering, is an effective measure to enhance rice yield and quality. This study aimed to obtain the mechanized-transplanting trajectory and attitude of rice pot seedlings by utilizing non-circular planetary-gear trains, focusing on the three key actions of rice pot-seedling transplanting: seedling picking, conveying, and planting. A lightweight and simplified rice pot-seedling transplanting machinery was designed, referring to the motion characteristics of artificially transplanting rice pot seedlings by first pulling them out and then planting them. Key technologies such as non-circular gear trains, the rice seedling supply system, the transmission system, and the rice seedling-picking device were studied, and their key components were designed and manufactured, resulting in the creation of two physical model machines: an ordinary ride type and a high-speed type. The seedling-picking test and field-transplanting test showed that the rice pot-seedling transplanting mechanism can accomplish the rice pot-seedling picking, rice conveying, and planting actions. The designed operation efficiency yielded a planting-depth qualification rate of over 92%, a seedling injury rate of less than 1.2%, and a missed-transplanting rate of less than 2%.

Effect of Different Methods and Planting Density on the Growth and Yield of Spring Rice at Tikapur, Kailali

A field experiment was conducted at Agronomy farm, Far Western University, Tikapur-1 to study the effect of different planting methods and density on yield of spring rice variety (chaite-4), when sown a month earlier than normal time. The research was laid out in randomized complete block design (RCBD) with seven treatments and three replications during Feb-June, 2022. The treatments consisted of planting methods viz. early broadcasting (T1 ), early line sowing (T2 ) on the day of nursery bed (1st Feb), transplanting 20 hills m-2(T3 ), transplanting 30 hills m-2 (T4 ), transplanting 40 hills m-2 (T5 ), late broadcasting (T6 ) and late line sowing, (T7 ) on the day of transplanting (2nd Mar). The results showed that transplanting significantly outperformed broadcasting method of rice planting in terms of yield attributing traits and yield. Broadcasting method showed significant reduction in tiller number, biological yield and grain yield than line sowing. But performance of late line sown rice was better than early line sown rice. Similarly transplanting 30 hills m-2 showed significant effect in early tiller formation followed by 20 hills-2resulting in significant increase in grain yield of spring rice as compared to transplanting 40 hills m-2. There was no difference in tiller number between line sown rice either early or late. This study recommends sowing of 30 hills m-2 and suggests further research on line sowing of spring rice at different dates ranging from 1st February to 3rd March at same planting density to define appropriate time for preponing planting time under similar condition.

Genetic Basis of Grain Size and Weight in Rice, Wheat, and Barley

Grain size is a key component of grain yield in cereals. It is a complex quantitative trait controlled by multiple genes. Grain size is determined via several factors in different plant development stages, beginning with early tillering, spikelet formation, and assimilates accumulation during the pre-anthesis phase, up to grain filling and maturation. Understanding the genetic and molecular mechanisms that control grain size is a prerequisite for improving grain yield potential. The last decade has brought significant progress in genomic studies of grain size control. Several genes underlying grain size and weight were identified and characterized in rice, which is a model plant for cereal crops. A molecular function analysis revealed most genes are involved in different cell signaling pathways, including phytohormone signaling, transcriptional regulation, ubiquitin–proteasome pathway, and other physiological processes. Compared to rice, the genetic background of grain size in other important cereal crops, such as wheat and barley, remains largely unexplored. However, the high level of conservation of genomic structure and sequences between closely related cereal crops should facilitate the identification of functional orthologs in other species. This review provides a comprehensive overview of the genetic and molecular bases of grain size and weight in wheat, barley, and rice, focusing on the latest discoveries in the field. We also present possibly the most updated list of experimentally validated genes that have a strong effect on grain size and discuss their molecular function.

Aphanomyces macrosporus sp. nov. Causing Root Rot in Barley and Some Other Plants.

In recent years, a new root rot disease in barley, which is caused by an Aphanomyces species, was found in field surveys in Southern Sweden and Denmark. Its symptoms occurred at the early tillering stage, around the BBCH 21 growth stage, and included the yellowing of leaves, brown coleoptiles, and the discolouration of roots. Prolonged soil wetness after rainfall favoured disease development, which sometimes advanced the yellowing patches to entire fields, resulting in lower yields. Oospores were found in the fine roots of diseased plants, and Aphanomyces isolates were obtained from these roots, as well as from the roots of barley plants grown in the greenhouse in soil samples from infected fields. Based on morphological analysis, we found that the new isolates were similar to those already obtained from barley and spinach roots in the 1990s in the same growing area. The morphological and molecular analyses performed in this study clearly separated and distinguished these barley isolates from other known Aphanomyces, and hereby Aphanomyces macrosporus sp. nov. is proposed as a new plant pathogenic species. It has larger oogonia and oospores than A. euteiches, A. cochlioides, and A. cladogamus, with one up to eight diclinous antheridia per oogonium. The phylogenetic analysis of the ITS rDNA region sequences grouped these new Aphanomyces isolates in a monophyletic clade, which was clearly distinguished from other plant pathogenic Aphanomyces species. The further pathogenicity of A. macrosporus on other plants is currently under investigation, but it is clear that it can at least infect barley, spinach, and sugar beet, indicating a wide host range for this species. The widespread presence and presumably broad host range of this new pathogenic Aphanomyces species must be considered in crop rotations.

Understanding the spatio-temporal behavior of crop yield, yield components and weed pressure using time series Sentinel-2-data in an organic farming system

ContextOrganic farming has begun to represent a practical alternative for reducing the environmental impact of crop production and increasing biodiversity. In agricultural systems, the growing demand for stable crop production requires the adoption of useful tools for the sustainable intensification of agriculture. While organic farming systems face various drawbacks, which affect crop yield. Among the limiting factors, weed management is one of the most difficult aspects of organic farming. ObjectiveThe aim of the study was (i) to evaluate the effect of weed pressure on yield spatial variability (ii) to analyze the spatial variability of yield and yield components based on hand-sampled yield data (iii) to evaluate the ability of the most commonly used vegetation index (NDVI) derived from Sentinel-2 satellite platforms to understand within-field spatial and temporal variability during the crop cycle (iv) to evaluate the ability of the cluster analysis procedures on NDVI satellite data to identify, discriminate and map sub-areas with different yield, yield components, and weed pressure at the farm level in an organic farming system. MethodsRemote sensing techniques (Sentinel-2 images), vegetation index (NDVI), cluster analysis (Hierarchical clustering Ward’s minimum variance approach) and hand-sampled data (georeferenced yield and yield components field data) were used for understanding the spatio-temporal behavior of crops. Results and conclusionsThe cluster analysis of NDVI data from Sentinel-2 collected at eight different stages detected the crop spatial and temporal variability at an early stage. In an open field of 24 ha, an area of about 9 ha, showed a high weed level with a yield average value 78 % lower than the most productive cluster area. The yield components, especially the spike number per square meter, also recorded very low values, mainly due to the negative effect of the high presence of weeds (in particular oats), which reached average values of 250 g m-2. An area of 7.3 ha showed the highest yield at harvest with a yield value 45 % higher than the mean harvest data. The study highlights that from the early tillering stage to the booting stage the NDVI maps derived from the Satellite Sentinel-2 and clustered by Ward’s method represent the weeds distribution impact on crop yield and yield components and an early warning for the assessment of one of the most important limiting factors in organic farming. SignificanceSentinel-2 data and cluster analysis can improve an efficient assessment and management strategies in an organic farming agricultural system. Furthermore, the use of precision agriculture tools in organic farming can lead to a site‐specific management at the farm level and therefore a sustainable intensification of agriculture systems.

Differential responses of soil bacterial communities to elevated CO2 between strongly CO2-responsive and weakly CO2-responsive rice cultivars

Effects of elevated CO2 (eCO2) on paddy soil microbial communities remain unclear, particularly when different rice cultivars exposed to eCO2. We thus compared responses of soil bacterial communities to ambient CO2 (aCO2) and eCO2 (aCO2 + 200 μmol CO2 mol−1) between two weakly CO2-responsive (Wuyunjing27, W27; Huaidao5, H5) and two strongly CO2-responsive rice cultivars (Yongyou1540, Y1540; LongIIyou1988, L1988) throughout six growth stages (early tillering, late tillering, jointing, heading, grain filling and ripening) in a paddy field in Jiangdu, China in 2018. No significant changes in soil bacterial diversities were observed between eCO2 and aCO2 or between cultivars for any single growth stage at the OTU level, but α diversity significantly changed at the phylum level except for the ripening stage. For a single cultivar, particularly two strongly CO2-responsive cultivars, over their whole growth stage, eCO2 enhanced differences in bacterial β diversity at both OTU and phylum levels under H5, Y1540 and L1988. Soil bacterial community complexity at the phylum level under eCO2 was weakened under W27, H5 and Y1540, but enhanced under L1988. eCO2-induced changes in soil DOC under these four cultivars had significantly positive impact on bacterial abundances. However, structural equation modeling illustrated that changes in soil DOC induced by eCO2 significantly decreased soil bacterial community richness. eCO2 did not significantly affect relationships between soil bacterial community diversities and rice yields, but displayed significantly negative correlations between strongly CO2-responsive rice cultivars' yields and relative abundances of Proteobacteria at the ripening stage. Dynamics that how soil microbial communities can differentiate their eCO2 responses between strongly- and weakly-responsive rice cultivars will provide a new insight into promoting rice productivity and soil health.

Nitrogen fertilization levels and timing affect the plasticity of yield components in bread wheat (Triticum aestivum L.)

The plasticity of grain yield components typically follows a hierarchy, with early-forming components having greater plasticity than late components (tiller number > spike number > grain number > grain weight). The first aim of this study was to assess the plasticity of two previously unexplored yield sub-components in wheat, i.e. spikelets per spike and grains per spikelet, and of other yield-related variables, i.e. straw mass, plant height, ovary mass and harvest index. The second aim was to test the potential limits of the phenotypic plasticity of yield components, and the relationships between them, by applying sudden strong changes in resource availability (via nitrogen fertilization)at different times during the crop cycle. Nitrogen (N) fertilization was applied only early (60 kg ha-1 of N, early tillering) or only late (120 kg ha-1, early stem elongation), very late (120 kg ha-1, late stem elongation) or extremely late (120 kg ha-1, pollination), never (N0) or multiple times (total of 300 kg ha-1) during the growth cycle of both a small-fruited (Bologna) and a large-fruited (Bora) bread wheat (Triticum aestivum L.) cultivar. Yield and grain number increased with fertilization levels in both cultivars, with the 300 kg N ha-1 treatment having the highest yield. Grain weight also increased with fertilization levels, but only when considering different N levels applied early.Delaying fertilization reduced yield, but increased grain weight, creating a tradeoff between yield (and grain number) and grain weight. Similarly, the relationships between other yield components and variables varied when considering N timing or levels. The plasticity of yield components, expressed as total variation of the trait over the trait value for the N0 (i.e. control) treatment, was 26.5%, 30.5%, 61%, 75% and 22%, respectively for tiller number, spike number, spikelets/spike, grains/spikelet and grain weight. The plasticity of grains/spike, grain number, yield, straw biomass, plant height, ovary mass and harvest index, was 174%, 236% and 268%, 417%, 54%, 54% and 36.5%, respectively. The results show that the plasticity of yield components (and other variables) may differ with different sources of environmental variation, explaining why, in the literature, two traits may be found to correlate both positively, negatively (tradeoff) or not at all. These results further our knowledge on the plasticity of, and the relationships among, yield components, and may be useful for further improvements of yield with agronomic intervention or breeding.

Rice demands higher nitrogen fertilizer during grain filling stage under elevated atmospheric CO2 condition

An experiment was conducted in open top chamber (OTC) to determine the response of rice to elevated carbon dioxide (eCO2) under varying time of nitrogen (N) application. Rice was grown in OTC with 500 ppm CO2 (eCO2), 450 ppm CO2 (intermediate CO2, iCO2), ambient CO2 (aCO2) and open field (OF, 380 ppm CO2). The timings of N application were N1 = 1/3rd N at early tillering (ET) + 1/3rd at active tillering (AT) + 1/3rd before panicle initiation (PI) stage, N2 = 1/3rd N at ET + 1/3rd before PI + 1/3rd at booting stage (BS), and N3 = 1/3rd N at ET + 1/3rd before PI + 1/3rd at flowering stage (FS). The results revealed that photosynthesis (Pn), shoot and root dry matter (SDM and RDM) production, yield and yield components were favored at eCO2 when N application scheduled from ET to FS of rice. Interestingly, the N application up to FS of rice showed significant improved grain fertility and reduced sterility under rising CO2. However, rice plant accumulated and translocated more nutrients from shoot to grain under elevated CO2 (eCO2) condition. Moreover, higher grain amylose and lower protein was obvious at eCO2. Collectively, rice yield increased by 18 to 20 % under eCO2 with the application of N at FS of rice. These results indicate that to maximize rice yield under eCO2, it is crucial to supply N at FS of rice in order to increase grain fertility and reduce spikelet sterility

Delaying tillering nitrogen topdressing until the midtillering phase improves nitrogen use efficiency and reduces ammonia emission via rice canopy recapture

Tillering nitrogen (N) topdressing is commonly employed to enhance primary-tiller number and achieve a high grain yield for wetland rice. Unfortunately, farmers typically apply N fertiliser shortly at tillering initiation following basal fertilisation, and substantial soil ammonia (NH3) volatilisation occurs due to the low N demand of small plants. Herein, we hypothesised that delaying topdressing N until the midtillering phase could increase canopy recapture of soil NH3 emission and better synchronise N supply with crop N demand, leading to reduced NH3 losses and increased fertiliser N use efficiency. A field experiment was conducted to investigate the effect of conventional tillering N topdressing (CT) at the early tillering stage (2 weeks after basal N application) and delayed tillering N topdressing (DT) until the midtillering phase (∼4 weeks after basal N application) on NH3 emission from soil and the soil-plant system, as well as N uptake, N use efficiency and yield. The 2-year field results showed that DT did not hinder effective tiller production or above-ground dry biomass compared with CT, but improved plant N uptake and total N accumulation after midtillering, leading to 18–27 % higher agronomic efficiency. Correspondingly, 8.9–15 % increases in grain yield were observed for DT compared with CT, mainly attributable to increased panicle number per area and filled grain number per panicle. Following tillering N application, NH3 loss from the soil-plant system under CT accounted for 22 % of top-dressed N, showing only a slight decline compared with that of soil emission. For DT, NH3 loss from the soil-plant system was reduced to 6 %, even though 15 % soil NH3 emission was observed, indicating a more than two-fold increase for in-canopy NH3 recapture. Correspondingly, cumulative net NH3 losses for the entire rice season were decreased by 31% under DT relative to CT. These results provide evidence that delaying tillering N topdressing until the midtillering phase when rice canopy formation is enhanced, can better synchronise fertiliser N supply with crop demand and increase in-canopy NH3 recapture. A large discrepancy remains between NH3 emission from soil and the soil-plant system at midtillering and panicle initiation stages, highlighting the overestimation by the soil dynamic chamber method when quantifying NH3 losses due to overlooking the contribution of canopy recapture of soil-emitted NH3.

Simulation of winter wheat response to variable sowing dates and densities in a high-yielding environment.

Crop multi-model ensembles (MME) have proven to be effective in increasing the accuracy of simulations in modelling experiments. However, the ability of MME to capture crop responses to changes in sowing dates and densities has not yet been investigated. These management interventions are some of the main levers for adapting cropping systems to climate change. Here, we explore the performance of a MME of 29 wheat crop models to predict the effect of changing sowing dates and rates on yield and yield components, on two sites located in a high-yielding environment in New Zealand. The experiment was conducted for 6 years and provided 50 combinations of sowing date, sowing density and growing season. We show that the MME simulates seasonal growth of wheat well under standard sowing conditions, but fails under early sowing and high sowing rates. The comparison between observed and simulated in-season fraction of intercepted photosynthetically active radiation (FIPAR) for early sown wheat shows that the MME does not capture the decrease of crop above ground biomass during winter months due to senescence. Models need to better account for tiller competition for light, nutrients, and water during vegetative growth, and early tiller senescence and tiller mortality, which are exacerbated by early sowing, high sowing densities, and warmer winter temperatures.

Grain yield and kernel setting of multiple-shoot and/or multiple-ear maize hybrids

Rainfed maize ( Zea mays L.) crops in low-rainfall regions are cultivated at very low plant population densities that favor the production of fertile tillers or multiple ears in the main shoot. Little information exists regarding the functional processes governing grain yield and kernel setting on ears of different order of shoots of maize crops. To study these functional processes, field experiments were conducted cultivating two commercial maize hybrids (AX7784 and DM2738) under supplementary irrigation using different plant densities, N rates at sowing, shading around female flowering (silking) and tiller removal treatments. Hybrids differed in the number of tillers per plant at R 1 (AX7784 > DM2738). Early tiller removal increased main shoot growth rate around silking, suggesting competition for light among shoots. Kernel number per plant was positively and curvilinearly related with plant growth rate around silking, i.e. critical period (PGR CP ), in tillered and non-tillered plants of both hybrids. Tillered plants set higher kernel numbers than non-tillered plants at PGR CP > 9 g pl -1 d -1 (AX7784) or 11 g pl -1 d -1 (DM2738), while the opposite trend occurred at PGR CP values < 9 g pl -1 d -1 (both hybrids). In both hybrids, the combination of a higher biomass partitioning to but a lower reproductive efficiency of ears of tillers than of main shoots resulted in a lower kernel number for tillers than for main shoots. Genotypic differences were evident in kernel setting between main shoots (DM2738 > AX7784) and tillers (AX7784 > DM2738). The different pattern of kernel setting between hybrids was explained by differences in the biomass partitioning to tiller ears and the reproductive efficiency of ears of tillers (AX7784 > DM2738), and both the biomass partitioning to and the reproductive efficiency of second and third order ears of main shoots (DM2738 > AX7784). Kernel number per plant was higher for DM2738 due to a higher kernel setting on multiple ears of main shoot plus tillers (more prolific and with lower tiller fertility) than for AX7784 (less prolific and with higher tiller fertility). However, grain yield did not differ between hybrids, because of the higher kernel weight of AX7784. Therefore, this work opens avenues for exploiting higher grain yields in maize crops with low plant population densities through the combination of prolificacy and tillering. Further studies should analyze the impact of reproductive plasticity on kernel weight determination in low-density maize crops. • We studied maize tiller and main shoot grain yield and kernel set determinants. • Tillered plants set more kernels than non-tillered ones at high plant growth rates. • Tillers featured higher biomass partitioning to first order ears than main shoots. • Ears of tillers featured lower reproductive efficiency than ears of main shoots. • The tillering and prolific hybrid featured the highest plasticity, without grain yield differences between hybrids.

Assessing the product quality and biological activities of barley (Hordeum vulgare L.) grasses at different harvest times

Barley (Hordeum vulgare L.) grasses (BG) have attracted considerable interest due to their multiple physiological activities and health benefits. In this paper, eight BG at four different growth stages were collected: seedling, tillering, stem elongation, and heading, and their product qualities and biological activities were examined and studied. Results demonstrated that harvest time obviously influenced proximate composition, surface color, and amino acid profile. Z21 and Z23 harvested at the seedling and early tillering stages, respectively, had higher total phenolic content (TPC) and total flavonoid content (TFC) than the other BG. Moreover, Z21 and Z23 possessed better DPPH radical-scavenging ability, antioxidant capacity, and α-glucosidase inhibitory activity, which were positively correlated with TPC, TFC, and protein and total amino acid contents. Our findings suggested that the early tillering stages were the preferable harvest times for BG with good product quality and biological properties.

Linking grain yield and lodging resistance with growth patterns in rice

Abstract Improving grain yield and lodging resistance are two important targets for improving rice production. The aim of this study was to link grain yield and lodging resistance with growth patterns in rice. A nitrogen (N) fertilization experiment was conducted in 2020 and 2021, which consisted of two N rates (150 and 225 kg ha–1) and three N split-application ratios among the basal, early tillering, and panicle initiation stages (6:3:1, 5:3:2, and 4:3:3). The results demonstrated that increasing the N rate from 150 to 225 kg ha–1 did not affect grain yield but increased the plant lodging index by 16%. This increase in the plant lodging index was attributable to a higher plant fresh weight resulting from improved post-heading growth and a lower plant lodging load, which was partially due to a higher leaf area index. Altering the N split-application ratio from 6:3:1 to 4:3:3 increased grain yield by 4% but did not affect the plant lodging index in rice. The increase in grain yield was due to improved post-heading growth mainly resulting from increased radiation use efficiency during the post-heading period, which was partially attributable to increased specific leaf weight. An improvement in pre-heading growth in 2021 did not affect grain yield but increased the plant lodging load and decreased the plant lodging index by 36% compared to 2020. The improvement in pre-heading growth was due to a higher intercepted solar radiation resulting from higher leaf area index and incident solar radiation during the pre-heading period. The results of this study indicate that improving pre-heading growth can maintain grain yield and increase lodging resistance, while improving post-heading growth by increasing canopy radiation use efficiency (but not the leaf area index) can increase grain yield and maintain lodging resistance.