Canopy Apparent Photosynthesis Research Articles

Improving Tuber Yield of Tiger Nut (Cyperus esculentus L.) through Nitrogen Fertilization in Sandy Farmland.

The cultivation of tiger nut (Cyperus esculentus L.) on marginal lands is a feasible and effective way to increase food production in Northern China. However, the specific influence of nitrogen fertilizer application on the growth dynamics, tuber expansion, overall yield, and nitrogen use efficiency (NUE) of tiger nuts cultivated on these sandy lands is yet to be fully elucidated. From 2021 to 2022, we conducted a study to determine the effect of N fertilizers on the leaf function morphology, canopy apparent photosynthesis (CAP), tuber yield, and NUE of tiger nut. The results indicate that the tuber yield and NUE are closely related to the specific leaf area (SLA), leaf area index (LAI), leaf nitrogen concentration per area (NA), CAP, and tuber expansion characteristics. Notably, significant enhancements in the SLA, LAI, NA, and CAP during the tuber expansion phase ranging from the 15th to the 45th day under the 300 kg N ha-1 treatment were observed, subsequently leading to increases in both the tuber yield and NUE. Moreover, a maximum average tuber filling rate was obtained under the N300 treatment. These improvements led to substantial increases in the tuber yield (32.1-35.5%), nitrogen agronomic efficiency (NAE, 2.1-5.3%), nitrogen partial factor productivity (NPP, 4.8-8.1%), and nitrogen recovery efficiency (NRE, 3.4-5.7%). Consequently, 300 kg N ha-1 of N fertilizers is the most effective dose for optimizing both the yield of tiger nut tubers and the NUE of tiger nut plants in marginal soils. Structural equation modeling reveals that N application affects the yield and NUE through its effects on leaf functional traits, the CAP, and the tuber filling characteristics. Modeling indicates that tuber expansion characteristics primarily impact the yield, while CAP predominantly governs the NUE. Above all, this study highlights the crucial role of N fertilizer in maximizing the tiger nut tuber yield potential on marginal lands, providing valuable insights into sustainable farming in dry areas.

Optimal row spacing configuration to improve cotton yield or quality is regulated by plant density and irrigation rate

ContextConventional high-density planting of machine-picked cotton in Xinjiang is associated with poor light distribution and low fiber quality. The objective of this study was to assess how different row spacing configurations, irrigation rates, and planting densities impact cotton photosynthetic production and fiber quality. MethodsWe conducted a 3-year field experiment in Shihezi, Xinjiang, China, to evaluate the impact of different row spacing configurations and irrigation amounts on cotton photosynthesis and fiber quality. The four row spacing configurations used were: RS66+10H (high-density with 66 +10 cm spacing), RS66+10L (low-density with 66 +10 cm spacing), RS76H (high-density with 76 cm spacing), and RS76L (low-density with 76 cm spacing). Additionally, two irrigation amounts were tested: MD-T3 (mulch drip irrigation with three tapes on one film) and MD-T2 (mulch drip irrigation with two tapes on one film). We measured and compared the distribution of cotton canopy leaves, light, canopy apparent photosynthesis, reproductive organs and fiber quality among these groups. ResultsThe results showed that RS66+10H had a higher lint yield than RS76L under MD-T2, with an increase of 5.4–7.1%. This can be attributed to the higher fraction of photosynthetically active radiation, canopy apparent photosynthesis (CAP), and boll biomass in RS66+10H between the full boll and boll opening stages. The maximum lint yield (3227–3580 kg ha−1) was obtained in RS66+10H under MD-T3. Interestingly, RS76L had a similar lint yield to RS66+10H under MD-T3, mainly due to the middle and lower canopy having higher leaf area index (LAI) values ranging from 1.8 to 2.1. This resulted in increased CAP and cotton boll biomass of the middle and lower canopy compared to RS66+10H during the full boll to boll opening stage. Under MD-T3, RS76L also exhibited longer fiber length in the middle and lower canopy (30.2–32.0 mm and 31.6–33.3 mm, respectively) compared to RS66+10H, with a difference of 3.2–3.8% and 5.6–6.5%. Furthermore, RS76L demonstrated higher fiber strength in the middle and lower canopy (31.4–32.7 cN tex−1 and 33.2–33.9 cN tex−1, respectively) compared to RS66+10H, with a difference of 2.6–6.2% and 5.9–6.8%. Maintaining an LAI of around 2.0 during the transition from full boll to boll opening stage optimized canopy architecture and enhanced photosynthetic productivity. ConclusionUnder adequate irrigation, RS76L could be a suitable replacement for RS66+10H in order to improve cotton fiber quality by optimizing leaf-boll spatial distribution. This study provides guidance for selecting the appropriate row spacing configuration under different water conditions. RS66+10H is recommended for increasing yield under water-deficient conditions, while RS76L is suitable for improving fiber quality under adequate irrigation.

Efficient cotton population photosynthetic production synergistically increases seedcotton yield and fiber quality through straw incorporation with appropriate nitrogen fertilization in wheat-cotton rotation system

ContextStraw incorporation with appropriate nitrogen (N) fertilization could increase seedcotton yield, but it is unknown whether and how straw incorporation with N fertilization can synergistically improve seedcotton yield and fiber quality. ObjectiveContinuous years of positioning field wheat-cotton double cropping experiments were conducted from 2015 to 2021 to investigate the effects of straw incorporation and N fertilization on seedcotton yield and fiber quality. MethodsFour N rates (0, 75, 150 and 300 kg N ha−1) and two straw managements (wheat-cotton straw incorporation and straw removal i.e. CK) were used as experimental treatments. The canopy photosyhthetic capacity, biomass, seedcotton yield and fiber quality were measured. Meanwhile, the dynamics of cotton square nuber and boll number during the efficient photo-thermal periods (approximately from 25th July to 30th August) were monitored. ResultsIn the study from 2019 to 2021, the canopy apparent photosynthesis rate, leaf area index and chlorophyll relative content increased with straw incorporation and increasing N rates. The maximum daily square appearance rate of 6.9 × 104 no. ha−1 and the maximum daily boll setting rate of 3.4 × 104 no. ha−1 during the efficient photo-thermal periods were obtained under straw incorporation with 150 kg N ha−1. Where the maximum boll setting ratio and boll weight ratio were observed. Straw incorporation with 150 kg N ha−1 also produced the maximum boll number (87.3–98.1 × 104 no. ha−1), seedcotton yield (3998–4544 kg ha−1) and the longest fiber length of 30.3–31.2 mm across from 2019 to 2021, and the strongest fiber strength and the lowest micronaire in 2019 and 2020. The results of 13CO2 feeding to cotton plants in 2019 and 2020 showed that straw incorporation promoted 13C allocation into cotton fiber and the maximum cotton fiber 13C proportion appeared under straw incorporation with 150 kg N ha−1. Besides, straw incorporation and increasing N rates increased seed hull 13C proportion for fiber development. In addition, long-term straw incorporation could reduce chemical N fertilizer by approximatly 30% from 150 kg N ha−1 to achieve the seedcotton yield under 150 kg N ha−1 without significant influence on fiber quality. ConclusionIn wheat-cotton rotation system, straw incorporation with a 30% reduction from 150 kg N ha−1 was appropriate to increasing seedcotton yield and fiber quality synergistically by improving canopy photosynthetic capacity, increasing cotton square and boll number during the efficient photo-thermal period, and optimizing photosynthate allocation in cotton boll.

Canopy Structure, Light Intensity, Temperature and Photosynthetic Performance of Winter Wheat under Different Irrigation Conditions.

A high-quality canopy architecture is central to obtaining high crop yields. A field experiment was carried out at the Wuqiao Experimental Station from 2015 to 2019 under four irrigation schemes (W0, no irrigation after sowing; W1, 75 mm irrigation at jointing stage; W2, 75 mm irrigation at jointing and anthesis stages, respectively; W3, 75 mm irrigation at tillering, jointing and anthesis stages, respectively) to investigate the canopy structure, canopy apparent photosynthesis (CAP), canopy temperature (CT), yield and water use efficiency (WUE). The results showed that increasing irrigation times improved the leaf area index (LAI), non-leaf area index (NLAI) and light interception (LI) of the spike and total canopy but decreased the canopy temperature (CT) after anthesis. The CAP in the W3 treatment was consistently lower than that in the W1 treatment, suggesting lower effective utilization of light energy under the W3 treatment. Increasing irrigation times improved wheat yield, but the W2 treatment had no significant difference in yield compared to the W3 treatment. In addition, the W1 and W2 treatments had higher WUEs. The CT, organ temperature and LI were closely positively associated with each other, but they were all strongly negatively related to the yield. Overall, the W2 treatment was the best irrigation scheme for constructing a reasonable canopy architecture for winter wheat, obtaining more efficient water use and yield in the North China Plain (NCP). CT and organ temperature can be used as proxy parameters to estimate the canopy structure.

Terminal removal at first square enhances vegetative branching to increase seedcotton yield at low plant density

ContextCotton has a complex branching pattern including sympodial and vegetative branching. Traditionally managed cotton mainly depends on sympodial branching for formation of yield-contributing fruit. Whether seedcotton yield based solely on vegetative branching is comparable with that based solely on sympodial or both types of branching is unclear. ObjectiveThe study determined how terminal removal at first square to avoid formation of sympodial branches (SBs) regulated vegetative branching and yield under different plant densities. MethodsA two-year split-plot design field experiment had main plots with plant density (4.5 and 9.0 plants m−2) and subplots with plant pruning mode. Pruning modes were terminal removal at first square (TRS) to avoid formation of sympodial branches but retain only vegetative branches (VBs), removal of VBs (RVB) to retain only SBs, and no pruning (CK), with both branch types remaining intact. Canopy photosynthesis, dry matter accumulation and partitioning, and seedcotton yield and yield components were examined. ResultsAt low plant density (4.5 plants m−2), compared with other pruning modes, TRS increased seedcotton yield and biological yield but did not affect harvest index. At high plant density (9.0 plants m−2), compared with other pruning modes, TRS decreased seedcotton yield and harvest index, although biological yield increased. The yield increase with TRS at low plant density was attributed to the increase in biological yield, which was due to significantly higher canopy photosynthesis with TRS than with other pruning modes. At high plant density, photosynthesis with TRS was higher than that with no pruning at peak boll-setting and boll-opening stages and higher than that with RVB from peak squaring to boll-opening. Compared with other pruning modes, TRS increased dry matter partitioning to vegetative organs but decreased partitioning to reproductive organs. Pearson correlation analysis revealed a significant positive correlation between canopy apparent photosynthesis and biological yield, biomass partitioning, and harvest index, irrespective of plant pruning and plant density. ConclusionPlant pruning and plant density interacted to affect seedcotton yield. With TRS, cotton yield at low plant density was higher than that with other pruning modes, which was attributed to an increase in biological yield associated with an increase in canopy photosynthesis. At high plant density, the yield decrease with TRS was attributed to low harvest index associated with reduced reproductive partitioning. ImplicationsCotton cultivation relying solely on vegetative branching can be an alternative to obtain moderate yields and economic benefits under conditions of low plant density.

Optimal planting pattern of cotton is regulated by irrigation amount under mulch drip irrigation.

It is of great importance to explore agronomic management measures for water conservation and cotton yield in arid areas. A four-year field experiment was conducted to evaluate cotton yield and soil water consumption under four row spacing configurations (high/low density with 66+10 cm wide, narrow row spacing, RS66+10H and RS66+10L; high/low density with 76 cm equal row spacing, RS76H and RS76L) and two irrigation amounts (CI:conventional drip irrigation; LI:limited drip irrigation) during the growing seasons in Shihezi, Xinjiang. A quadratic relationship was observed between the maximum LAI (LAImax) and seed yield. Canopy apparent transpiration rate(CAT), daily water consumption intensity (DWCI) and crop evapotranspiration (ETC) were positively and linearly correlated with LAI. The seed yields, lint yields, and ETC under CI were 6.6-18.3%,7.1-20.8% and 22.9-32.6%higher than those observed under LI, respectively. The RS66+10H under CI had the highest seed and lint yields. RS76L had an optimum LAImax range, which ensured a higher canopy apparent photosynthesis and daily dry matter accumulation and reached the same yield level as RS66+10H; however, soil water consumption in RS76L was reduced ETC by 51-60 mm at a depth of 20-60 cm at a radius of 19-38 cm from the cotton row,and water use efficiency increased by 5.6-8.3%compared to RS66+10H under CI. A 5.0<LAImax<5.5 is optimum for cotton production in northern Xinjiang, and RS76L under CI is recommended for high yield and can further reduce water consumption. Under LI, the seed and lint yield of RS66+10H were 3.7-6.0% and 4.6-6.9% higher than those of RS76L, respectively. In addition, high-density planting can exploit the potential of soil water to increase cotton yields under water shortage conditions.

Whole-Canopy Photosynthetic Characterization of Apple Tree and the Effects Induced by Grafting on Rootstocks with Different Vigor

Leaf photosynthesis is pivotal for the synthesis of carbohydrates; however, the growth and development of horticultural crops are more closely related to canopy photosynthetic capacity. Measurements of canopy photosynthesis allow a better evaluation of the fruit tree performance at the canopy scale. Therefore, an open chamber system to determine instantaneous canopy apparent photosynthesis (CAPi) was investigated. CAPi slightly overestimated the biomass accumulation by 5.9%, which revealed that the CAPi method is valuable for quantifying canopy photosynthesis. Further, many woody horticultural plants are usually grafted for propagation, such as apples, whereas the rootstocks always influence the canopy size and photosynthesis. In this study, the effect of dwarfing, semi-dwarfing, and vigorous apple rootstocks on canopy photosynthesis was studied. Compared to vigorous rootstock, dwarfing rootstock significantly reduced the leaf net photosynthetic rate and total leaf area by 20.8% and 53.1%, respectively, and resulted in a 59.7% reduction in CAPi. Throughout the study, CAPi was an effective method that should be considered for canopy photosynthesis measurement of horticultural crops in the future.

Wide belt sowing improves the grain yield of bread wheat by maintaining grain weight at the backdrop of increases in spike number.

Increasing the seeding belt width from 2 to 3 cm (conventional drilling sowing, CD) to 8–10 cm (wide belt sowing, WB) can markedly improve the grain yield of bread wheat. However, there are insufficient data to explain how WB affects dry matter (DM) remobilization, pre- and post-anthesis production, and ultimately grain weight and grain yield. In the present study, four bread wheat cultivars (Jimai44, Taishan27, Gaoyou5766, and Zhouyuan9369) with similar phenology characteristic were selected as experimental materials and two sowing patterns (CD and WB) were applied during the 2018–2019 and 2019–2020 growing seasons, to investigate the effects of sowing pattern on grain yield and its components of bread wheat. The results showed that WB increased the post-anthesis rate of canopy apparent photosynthesis (CAP) in comparison with CD, by 19.73–133.68%, across the two seasons and four bread wheat cultivars. Furthermore, WB significantly increased the activities of superoxide dismutase, peroxidase, and catalase, and decreased the malondialdehyde content of the flag and penultimate leaf, thereby extending the duration of the high-value CAP period by 1.95–2.51 days. The improved rate and duration of CAP in WB led to an increase in post-anthesis DM production of 13.33–23.58%, thus ensuring DM distribution to the grain of each bread wheat cultivar. Consequently, in WB, the grain weight was maintained, the grain yield was increased markedly by 9.65–15.80%, at the backdrop of increases in spike number and in turn grain number per unit area. In summary, WB could be applied widely to obtain a high yield of bread wheat.

Fertilizer Reduction Combined with Organic Liquid Fertilizer Improved Canopy Structure and Function and Increased Cotton Yield

The application of organic liquid fertilizer combined with chemical fertilizer is one of the key technologies used to simultaneously improve cotton yield and efficiently utilize resources. However, organic fertilizer is usually applied once as a base fertilizer during production, and few studies have been conducted on topdressing with water during the growth period. Therefore, in this study, Xinluzao 74 was used as the experimental material, and a single fertilizer application (CF) was used as a control in 2019–2020 under the conditions of integrated control of water and fertilizer with mulch drip irrigation. Five combinations of reduction in chemical fertilizer combined with organic fertilizer (OF1, OF2, OF3, OF4, and OF5) were used to investigate the influences of chemical fertilizer combined with organic liquid fertilizer on the leaf area index (LAI), canopy openness (DIFN), mean foliage tilt angle (MTA), photosynthetically active radiation (PAR), canopy apparent photosynthesis (CAP), and yield and quality of cotton. The results show that among the different fertilization treatments, the OF2 treatment had the best results, not only ensuring a suitable LAI (4.8) and maintaining a large DIFN (0.1) but also increasing the light transmittance of the middle and lower canopies (0.02–0.03). At the same time, CAP increased significantly compared with that in the CF treatment, with an average increase of 12.8%. The high value lasted for a long time, and the late decay stage remained at 8.9 μmol m−2 s−1. The ratio of the population respiration rate to total photosynthesis (CR/TCAP) decreased significantly, with an average decrease of 13.5%. Compared with that in CF, the lint yield increased by 27.0% in the other treatments. The correlation analysis showed that lint yield was positively correlated with the relative chlorophyll content (SPAD value), PAR transmittance (PARU) and CAP in the upper canopy (p &lt; 0.05) and significantly negatively correlated with PAR transmittance (PARM) in the middle canopy and PAR transmittance (PARD) and CR/TCAP in the lower canopy (p &lt; 0.05). Therefore, under mulch drip irrigation, the OF2 treatment (OF + 80% CF) improved the canopy structure of cotton at the late growth stage, increased the population photosynthetic rate, and increased lint yield significantly; thus, this approach can be used as an effective fertilization method to achieve the goal of decreasing costs and increasing efficiency in cotton production.

Increasing seeding density under limited irrigation improves crop yield and water productivity of winter wheat by constructing a reasonable population architecture

Favorable crop population architecture is the foundation for obtaining high crop yields and water productivity (WP) under limited irrigation. A field experiment was conducted at Wuqiao Experimental Station from 2015 to 2018 using the ‘Nongda399′ wheat variety under the four seeding density and three irrigation schemes to explore the population architecture, canopy apparent photosynthesis (CAP), organ contribution, yield, and WP of winter wheat (Triticum aestivum L.). Compared with conventional high-yield cultivation (SD1W3), the water-saving cultivation (SD3W1) obtained a comparable yield meanwhile improved the WP in the range of 14.2–39.2%. The non-significant change in the yield under SD3W1 was primarily due to the increasing seeding density under W1 irrigation treatment, which improved the spike number and grains per unit area, especially the main stem spike, and had no significant effect on the thousand kernel weight (TKW). Increases in grain yield was generally caused by increases in CAP by constructing a reasonable canopy architecture with higher leaf area index (LAI) and non-leaf area index (NLAI) of the total canopy and upper strata, especially the spike area index (SAI) of the upper strata. Therefore, more light was intercepted by spikes, which improved the contribution of spike photosynthesis to yield. Increasing the seeding density also improved the assimilate remobilization contribution (RC) of pre-anthesis and decreased the post-anthesis leaf photosynthesis contribution to yield. Increasing the seeding density under limited irrigation improved the root length density (RLD), especially in 120–200 cm soil layer, which increased the absorption and use of deep soil moisture and improved WP. Overall, when sowing time from October 10–20, the appropriate seeding density of approximately 525–600 plants m−2 with 75 mm of irrigation at the jointing stage was the best cultivation practice for saving water and obtaining a comparable yield and a high water productivity of winter wheat in the North China Plain (NCP).

Straw returning coupled with nitrogen fertilization increases canopy photosynthetic capacity, yield and nitrogen use efficiency in cotton

Nitrogen (N) fertilization plays a pivotal role in canopy photosynthetic capacity and yield formation of cotton (Gossypium hirsutum L.), but the interaction effects with consecutive straw returning remain poorly understood. A field experiment was conducted (2015–2018) to examine the effects of N fertilization (0, 75, 150, and 300 kg N ha−1) coupled with or without barley and cotton straw supplementation on soil nutrient status, cotton canopy photosynthetic capacity, seedcotton yield, and nitrogen use efficiency (NUE) in Yancheng, China. N fertilization coupled with straw addition enhanced most cotton growth traits, showing higher canopy apparent photosynthesis rate, leaf area index, leaf N content, specific leaf area, and boll density, and progressively increased seedcotton yield annually. In 2018, straw addition increased seedcotton yield by 7.5 %, 9.6 %, 12.1 %, and 4.1 % under 0, 75, 150, and 300 kg N ha−1, respectively, compared to corresponding treatments of straw removal. The highest increase in seedcotton yield and NUE under 150 kg N ha−1 combined with straw addition was due to the greatest improvements in soil fertility, canopy photosynthetic capacity, and N uptake by cotton. In addition, the results suggested that approx. 33–44 % of chemical N fertilizer reduction would not affect seedcotton yield with straw addition. Our results demonstrated that straw returning combined with 150 kg N ha−1 had benefits on improving soil nutrient status, canopy photosynthetic capacity, seedcotton yield, and NUE of cotton.

Genetic progress in grain yield and the associated physiological traits of popular wheat in southwestern China from 1969 to 2012

AbstractKnowledge about the key traits related to genetic gains in grain yield (GY) is necessary for understanding the main yield‐limiting factors and guiding future wheat (Triticum aestivum L.) breeding. The objective of this research was to investigate the genetic progress in GY and the associated physiological traits in popular wheat cultivars released from 1969 to 2012 in southwestern China. Field experiments included eight representative cultivars that were evaluated at three experimental sites for three growing seasons. Grain yield increased at a linear rate of 0.69% or 52.52 kg ha−1 yr−1, which was mainly attributed to the increases in dry matter (DM) accumulation at maturity, harvest index (HI), and thousand‐kernel weight (TKW). The soil and plant analyzer development (SPAD) values of flag and penultimate leaves at anthesis increased with the year of release and were significantly related to GY. Significant genetic gains were made in both nonstructural carbohydrate (NSC) translocation and NSC translocation efficiency from anthesis to maturity, and there was a trend over time towards a high net photosynthetic rate (Pn) of flag leaf and canopy apparent photosynthesis (CAP) at anthesis and at 30 d post‐anthesis (DPA). In addition, the linear increases in N uptake efficiency and N utilization efficiency were both significant and positive related to GY. Therefore, these key physiological traits can be used as selection criteria for further improving yield potential. Our results also reveal the potential for using synthetic hexaploid wheat in high‐yielding wheat breeding.

Hormonal changes with uniconazole trigger canopy apparent photosynthesis and grain filling in wheat crop in a semi-arid climate.

Phytohormones are important for the growth and development of plants. The objective of the experiment was to investigate the effect of foliar application of uniconazole (UCZ) at the four-leaf stage on hormone crosstalk and production of winter wheat. An experiment was carried out during 2015-2016 and 2016-2017 growth season in a semi-arid region, where UCZ at a concentration of 0 (CK, distilled water), 15 (FU15), 30 (FU30), and 45 (FU45) mgL-1 were sprayed on wheat crop at the four-leaf stage at a rate of 138.8mLm-2. UCZ alters the endogenous hormone contents in flag leaves and in grains. UCZ inhibited gibberellic acid (GA) in flag leaves and in grains where the lower GA with UCZ improved the zeatin + zeatin riboside (Z + ZR) and abscisic acid (ABA) contents. The lower GA and higher Z + ZR and ABA contents with UCZ-treated plants improved the chlorophyll content and canopy apparent photosynthesis (CAP) as well as the grain-filling characteristics. The Z + ZR and ABA in flag leaves were positively correlated with chlorophyll content and CAP value while negatively with GA. Moreover, the Z + ZR and ABA were positively correlated with maximum grain weight, mean grain-filling rate, and maximum grain-filling rate, while negatively with GA level. Treatment FU30 significantly improved the chlorophyll content, CAP value, spike weight, grain-filling characteristics, and hormone contents of Z + ZR and ABA while it decreased the GA level. The hormone crosstalk with UCZ significantly increased the yield of wheat crop, where FU30 treatment performs better.

Crop residue incorporation combined with potassium fertilizer increased cotton canopy apparent photosynthesis and seed cotton yield in barley-cotton rotation system

ABSTRACT The field experiment was conducted to evaluate the effects of crop residue incorporation and K fertilizer on seed cotton yield, K uptake and canopy apparent photosynthesis. Without K fertilizer, barley residue incorporation and barley-cotton residue incorporation increased seed cotton yield, total biomass, K uptake, leaf K concentration, leaf area index and canopy apparent photosynthesis in 2017 and 2018, while cotton residue incorporation increased these factors in 2018 and with 150 kg ha−1 K2O, barley residue incorporation and barley-cotton residue incorporation increased K uptake and leaf K concentration in 2017 and 2018, while these factors were influenced by cotton residue incorporation in 2018. Thus, the effects of crop residue incorporation on cotton growth depended on K fertilizer rate. In addition, crop residue incorporation could reduce K fertilizer input to some extent. Based on yield, barley residue incorporation and barley-cotton residue incorporation could reduce 73.7 kg ha−1 K2O (49.1%) and 70.1 kg ha−1 K2O (46.7%) in 2017, 53.6 kg ha−1 K2O (35.7%) and 89.5 kg ha−1 K2O (59.6%) in 2018, while cotton residue incorporation could reduce 38.0 kg ha−1 K2O (25.4%) in 2018.

Mixed Cropping of Different Hybrids of Maize Optimizes Canopy Structure and Promotes Higher Grain Yield

Under high‐density planting, mixed cropping planting pattern can potentially optimize maize (Zea mays L.) canopy architecture and ultimately improve grain yield. The objectives of this study were to evaluate the effects of three plant patterns combined with three plant population densities (67,500, 82,500, and 97,500 plants·ha−1) on canopy architecture and grain yield. Zhengdan 958 (ZD958) and Denghai 605 (DH605) were used as experimental materials. Three different planting patterns were: mixture (M), random sowing after mixing seeds of the two hybrids in the same proportion; 1:1, one row of ZD958 and one row of DH605; and two monoculture systems, SZD958 and SDH605, as controls. A 3‐yr study demonstrated that the mixed cropping treatments (M and 1:1) at low density (LD) showed no significant difference on light transmission, leaf area index (LAI), canopy apparent photosynthesis (CAP), and canopy respiration (CR), compared with the two monocultures. However, at a medium and high density (MD and HD), mixed cropping was characterized with higher light transmission to the ear and lower layers of the canopy during grain filling than that of monoculture treatments, while no significant differences between M and 1:1 treatments. Moreover, mixed cropping treatments maintained a higher LAI, CAP, lower CR, and increased the whole and post‐silking dry matter accumulation. Grain yields were higher under mixed cropping at MD and high density (HD), while no significant differences between M and 1:1 treatments. Relative to SZD958 and SDH605, the grain yields in the M treatment were 10% and 8% higher at MD, and 7% and 5% higher at HD, respectively. Mixed cropping optimized the canopy structure, maintained higher LAI and CAP during the grain filling period, reduced respiration, and increased aboveground dry matter at maturity. These improvements also result in higher grain yield.Core Ideas Mixed cropping facilitated the formation of a high‐efficiency canopy structure. Mixed cropping delayed the rate of leaf senescence, maintained higher LAI and CAP during the grain filling period. Mixed cropping increased aboveground dry matter weight at physiological maturity, and ultimately led to higher grain yield, especially medium density.

Maize Canopy Apparent Photosynthesis and 13C-Photosynthate Reallocation in Response to Different Density and N Rate Combinations.

Appropriate planting density and nitrogen (N) supply are critical factors optimizing yield in crop cultivation. To advance the knowledge of maize plants under different density and N rate combinations, responses of canopy apparent photosynthesis (CAP), and assimilate redistribution characters (by 13CO2 stable isotope tracing) were investigated. In this study, two maize varieties DH618 and DH605 were grown at various planting densities (6.75, 8.25, 9.75, and 11.25 pl m−2) and N application rates (0, 180, 270, 360, and 540 kg ha−1) during 2013–2015. Maize grain yield (GY) was maximized at a density of 9.75 pl m−2 with 180–360 kg ha−1 N during the three study years. Maize GY, biomass, CAP, leaf area index (LAI), and 13C-photosynthate reallocation all responded more intensively to density than N rate, but the N response differed between varieties. We established links among CAP, LAI and biomass, and GY and kernel number per unit area (KNA). CAP depended on high LAI and enzyme activities for photosynthesis, yet both N deficiency and N excess had inhibitory effects. Besides, relations between 13C-photosynthate reallocation and yield components were executed. High density increased the 13C-photosynthate distribution in vegetative organs but reduced the allocation in ear, while N supply moderated the response. Based on our results, maize plants with greater CAP, more 13C-photosynthate distribution to ears, and less 13C-photosynthate distribution to stems under different density and N rate combinations could improve KNA and achieve a greater GY consequently.

Growth and yield of cotton as affected by different straw returning modes with an equivalent carbon input

Crop production is greatly affected by the applications of straw and straw-biochar. However, the responses of cotton (Gossypium hirsutum L.) growth and yield to different straw returning modes with an equivalent carbon (C) input are still unclear. A four-year field experiment was conducted to investigate the effects of different straw returning modes on the soil temperature, soil water content, soil nutrient availability, cotton root growth, cotton nutrient status, cotton canopy photosynthetic properties and seedcotton yield in a barley-cotton rotation system in Yancheng, China. Based on an equivalent C input, five treatments were set: straw-biochar incorporation (SB), straw incorporation with microbial inoculant (SI), straw incorporation (S), straw mulching (SM), and the control without straw or straw-biochar (CK). Treatments with straw and straw-biochar significantly enhanced most cotton growth parameters, and consequently increased the seedcotton yield from the second year to the fourth year. Such beneficial effects induced by the applications of straw and straw-biochar tended to progressively increase annually. In the fourth year, seedcotton yields in SB, SI, S and SM were significantly increased by 24.2%, 16.1%, 14.3% and 8.2%, respectively, compared with that of the control. The highest increase in seedcotton yield in SB was due to the greatest improvements in the contents of soil available nitrogen (N), phosphorus (P) and potassium (K); root biomass; NPK uptake by cotton; partitioning percentage of NPK to bolls; and canopy apparent photosynthesis rate. The lowest increase in seedcotton yield in SM was mainly ascribed to a reduction of 2.4–3.2 ℃ in the daily maximum temperature of topsoil at the early growth stage of cotton. Overall, compared with other crop straw returning modes, converting straw into biochar and incorporating it into fields could be an appropriate practice for sustaining high seedcotton yield in the barley-cotton rotation system.

Carbon cycle in response to residue management and fertilizer application in a cotton field in arid Northwest China

Understanding the influence of farming practices on carbon (C) cycling is important for maintaining soil quality and mitigating climate change, especially in arid regions where soil infertility, water deficiency, and climate change had significantly influenced on agroecosystem. A field experiment was set up in 2009 to examine the influence of residue management and fertilizer application on the C cycle in a cotton field in the Xinjiang Uygur Autonomous Region of Northwest China. The study included two residue management practices (residue incorporation (S) and residue removal (NS)) and four fertilizer treatments (no fertilizer (CK), organic manure (OM), chemical fertilizer (NPK), chemical fertilizer plus organic manure (NPK+OM)). Soil organic carbon (SOC) and some of its labile fractions, soil CO2 flux, and canopy apparent photosynthesis were measured during the cotton growing seasons in 2015 and 2016. The results showed that SOC, labile SOC fractions, canopy apparent photosynthesis, and soil CO2 emission were significantly greater in S+NPK+OM (residue incorporation+chemical fertilizer) than in the other treatments. Analysis of all data showed that canopy apparent photosynthesis and soil CO2 emission increased as SOC increased. The S+OM (residue incorporation+organic manure) and S+NPK+OM treatments were greater for soil C sequestration, whereas the other treatments resulted in soil C loss. The S+NPK treatment is currently the standard management practice in Xinjiang. The results of this study indicate that S+NPK cannot offset soil C losses due to organic matter decomposition and autotrophic respiration. Residue return combined with NPK fertilizer and organic manure application is the preferred strategy in arid regions for increasing soil C sequestration.

Comparison of Growth, Development, and Photosynthesis of Petunia Grown Under White or Red-blue LED lights

Red-blue (RB) LED lighting systems are widely used for plant cultivation because red and blue light are effectively absorbed by photosynthetic pigments. However, numerous studies have shown that RB LED light is either comparable to or less effective than white light in supporting plant growth. In this study, we compared the effects of RB or white LED light on growth, development, and photosynthesis of petunia (Petunia × hybrida Vilm.) plants. The plants in both treatments had similar shoot fresh weights, but the plants grown under white LED light had significantly higher shoot dry weight than those grown under RB LED light. Petunia plants grown continuously under RB light exhibited the higher single-leaf CO2 assimilation rate at 9 weeks after sowing but the lower maximum quantum efficiency and operating efficiency of PSII than those grown under white LED light. In another experiment, petunia plants were grown continuously under white LED light before measurements of single leaf CO2 assimilation rate and canopy apparent photosynthesis (CAP) under RB or white LED light. It was found that single leaf CO2 assimilation rates under RB light were higher than those under white light. However, CAP measured under RB light was either similar to or lower than that in plants measured under white LED light. White LED light had higher percentages of light transmission through the leaves than RB LED light. Results from this study suggest that white LED light could be more effective at supporting petunia plant growth than RB LED light because of its greater ability to transmit through leaves and drive photosynthesis at the canopy level.

Yield, growth, canopy traits and photosynthesis in high-yielding, synthetic hexaploid-derived wheats cultivars compared with non-synthetic wheats

Continuous improvement of potential yield is one of the most important goals of wheat breeding. The introduction of synthetic hexaploid wheat (SHW) germplasm has broken the bottleneck in potential yield, taking wheat breeding in China’s Sichuan Basin to a new level. However, systematic research on the physiological basis of high-yielding, SHW-derived cultivars has lagged behind. In the present study, three SHW-derived, high-yielding cultivars and three typical, non-synthetic cultivars widely used in wheat production were chosen for a 5-year study. Post-anthesis canopy structure, rates of canopy apparent photosynthesis (CAP), attenuation during grain filling, dry matter partitioning and other physiological parameters were studied. The average yield of the SHW-derived cultivars was 9154 kg ha–1, which was 13.5% higher than that of the non-synthetic cultivars. The increased yield was due to increased biomass and/or increased harvest index (HI). SHW-derived cultivars had shorter but wider flag leaves, with length : width ratio &lt;10. The basal angle and open angle were small at the beginning of anthesis, which gradually increased as grain-filling progressed; the SPAD readings of the flag leaf and penultimate leaf of the SHW-derived cultivars was significantly higher than that of the non-synthetic cultivars from anthesis to mid–late grainfill. The CAP values at anthesis and 20 days post-anthesis were significantly higher in the SHW-derived cultivars than in non-synthetic cultivars, in which the difference was most significant between 10 : 00 and 12 : 00. The dry matter partitioning at anthesis varied significantly among cultivars, and the stem and sheath proportion of the SHW-derived cultivars was larger than that of the non-synthetic cultivars. At maturation, the spike rachis and leaves of the SHW-derived cultivars accounted for significantly smaller proportions of the total aboveground dry weight. Accordingly, the grain proportion was increased by 1–4 percentage points. Yield components were closely related to measured physiological parameters; e.g. grain yield correlated positively with SPAD values (r = 0.960**) and negatively with the proportion of spike rachis at maturation (r = –0.946**). This indicated that a semi-compact plant morphology, with high SPAD readings and high CAP and greater HI, was the physiological basis of high yield in SHW-derived cultivars.