Experimental analysis of a nitrogen removal process simulation of wastewater land treatment under three different wheat planting densities

Nitrogen contaminant transport, transformation and uptake simulation experiments were conducted in green house under three different planting density of winter wheat. They were Group A, planting density of 0.0208 plants/cm 2, Group B, 0.1042 plants /cm 2, and Group C, 0.1415 plants/cm 2. The capacity and ratio of nitrogen removal were different on three kinds of conditions of wastewater land treatment. From analysis of wastewater treatment capacity, wastewater concentration and irrigation intensity for Group C were suitable and nitrogen quantity added was 2 times of that for Group B, 2.6 times for Group A while nitrogen residue was only 7.06%. Hence, wastewater irrigation and treatment design with purpose of waste water treatment should select the design with maximum capacity, optimal removal ratio and least residue in soil, which was closely related to crop planting density, crop growth status and also background nitrogen quantity in soil.

Environmental load of solid wood floor production from larch grown at different planting densities based on a life cycle assessment

As one of the main structural units in a building,a solid wood floor has significant strategic research value for low-carbon energy saving.Taking the production line of a solid larch wood floor as a case study,we assessed the environmental load during production based upon a life cycle assessment.Using GaBi 6.0 software,we analyzed the associated carbon sequestration during floor production,with the initial planting density serving as the disturbance factor in a modular analysis.The results indicated that the cutting and finishing steps have relatively intense,negative influences on the environment,whereas transportation,ripping,and trimming do not.Additionally,recycling biomass waste has the potential to reduce greenhouse gas emissions.When the initial planting density was 3.0×3.0 m,carbon sequestration was relatively high.Although the emissions of freshwater pollutants,volatile organic compounds,and fine particulate matter（matter with a 2.5-μm diameter） were comparatively high,the reduction of greenhouse gas emissions was still excellent at this planting density.

Alterations in Growth and Yield of Camelina Induced by Different Planting Densities under Water Deficit Stress

Camelina(Camelina sativa L.)is famous for its oil quality and unique fatty acid pattern.Growth and yield of crops reduced under water deficit conditions.Environmental threat such as drought or water deficit condition is the emerging problem which creates the negative impact on the growth of plants.Based upon the current situation a pot study was performed in rain out-shelter to explore the effect of different plant densities(15,10 and 5 plants per pot)on growth and seed yield of two camelina genotypes under normal(100%WHC)and water deficit(60%WHC)conditions by using completely randomized design with factorial arrangement having three replicates.Results indicated that individual effects of plant densities and water deficit stress levels considerably influenced the growth and seed yield of camelina but interaction effects did not indicate any significant variation.Maximum values of leaf area index(LAI)and crop growth rate(CGR)were recorded in P_(3) treatment(15 plants per pot).However,maximum values of leaf area duration(LAD),net assimilation rate(NAR),yield and yield components were observed in the treatment P_(1)(5 plants per pot).Water deficit condition(60%WHC)significantly minimized the growth,seed yield(0.82 g/m^(2))and yield components of camelina genotypes.Both camelina genotypes(611 and 618)did not differ significantly under water deficit conditions.

Leaf Photosynthetic Characteristics of High-Yield Soybean[Glycine max(L.)Merr.]Under Different Planting Densities,Different Fertilization Rates,and Single/Mixed Planting Patterns

Understanding the photosynthetic characteristics of high-yield soybean[Glycine max(L.)Merr]cultivar(HYC)would aid research aiming at investigating the soybean high yield formation mechanism and optimization of cultivation system.To assess the photosynthesis of HYC,a pot experiment was conducted to quantify the differences in photosynthetic characteristics between HYC and common-yield soybean cultivar(CC)under different planting densities,fertilization rates,and single/mixed planting patterns.The leaf greenness(Lg),net photosynthetic rate(Ph),stomatal conductance(St)and transpiration rate(Tr)were significantly higher in HYC than CC mainly in seed-filling stages.HYC was more tolerant to dense and mixed planting because the decreases of Ph and St under high planting density and those of Ph,St,and Tr under mixed planting were lower in HYC than CC.The Lg and Ph in HYC were more superior to those in CC at high fertilization rate.Thus,the HYC has a superior performance in photosynthetic characteristics under the varied cultivation practices,which may contribute to the greater seed yield in HYC than CC.

Effects of Different Planting Densities on the Yield of Rice Developed from Seedlings Dry Raised in Plug Trays

[Objectives]This study was conducted to investigate the effects of different planting densities on rice tillering dynamics and yield. [Methods]The effects of different planting densities on rice yield were studied based on seedlings dry raised in plug trays. [Results]Planting density had obvious effects on tillering dynamics,number of panicles per unit area,number of grains per panicle and rice yield under the condition of seedlings dry raised in plug trays. Comprehensive analysis showed that the row spacing × hill spacing = 25 cm × 14 cm,that is,the planting density of 2. 85 × 10~5 hills/hm^2,achieved the highest yield,at 9 960 kg/hm^2. [Conclusions]This study provides a scientific basis for optimizing rice cultivation techniques and achieving high yield and high efficiency in rice production.

Effects of Variety and Planting Density on Mung Bean Eco-Physiology and Yield in the Southeastern US

Mung bean (Vigna radiata L. Wilczek.) is a warm-season, C3 pulse crop of the legume family that has been widely cultivated in Asian countries. As the demand for mung bean continues to increase in the United States, the ecophysiology, growth, and yield of mung bean varieties in the southeastern US need to be assessed. A field experiment was conducted at the Agricultural Research and Education Center of Tennessee State University to investigate the effects of four varieties (OK2000, Berken, TSU-1, AAMU-1) and three planting densities (5, 10, and 15 cm spacing) on the ecophysiology and yield of mung bean. Results showed that the relative chlorophyll content, plant height, pod dry biomass, pod number, crop yield, and harvest index significantly varied among the varieties. Density only influenced transpiration, relative chlorophyll content, and plant dry biomass. OK2000 had 101.0% more pods per plant and a 42.4% higher harvest index and produced a 45.3% higher yield than other varieties, but no significant difference in yield was found among the other three varieties. This study demonstrated that the mung bean variety OK2000 with a high yield would be ideal for commercial production in the southeastern US.

Increasing photosynthetic performance and post-silking N uptake by moderate decreasing leaf source of maize under high planting density

To date,little attention has been paid to the effects of leaf source reduction on photosynthetic matter production,root function and post-silking N uptake characteristics at different planting densities.In a 2-year field experiment,Xianyu 335,a widely released hybrid in China,was planted at 60 000 plants ha^(–1 )(conventional planting density,CD) and 90 000 plants ha^(–1) (high planting density,HD),respectively.Until all the filaments protruded from the ear,at which point the plants were subjected to the removal of 1/2 (T1),1/3 (T2) and 1/4 (T3) each leaf length per plant,no leaf removal served as the control(CK).We evaluated the leaf source reduction on canopy photosynthetic matter production and N accumulation of different planting densities.Under CD,decreasing leaf source markedly decreased photosynthetic rate (P_(n)),effective quantum yield of photosystem II (ΦPSII) and the maximal efficiency of photosystem II photochemistry (F_(v)/F_(m)) at grain filling stage,reduced post-silking dry matter accumulation,harvest index (HI),and the yield.Compared with the CK,the 2-year average yields of T1,T2 and T3 treatments decreased by 35.4,23.8 and 8.3%,respectively.Meanwhile,decreasing leaf source reduced the root bleeding sap intensity,the content of soluble sugar in the bleeding sap,post-silking N uptake,and N accumulation in grain.The grain N accumulation in T1,T2 and T3 decreased by 26.7,16.5 and 12.8% compared with CK,respectively.Under HD,compared to other treatments,excising T3 markedly improved the leaf P_(n),ΦPSII and F_(v)/F_(m) at late-grain filling stage,increased the post-silking dry matter accumulation,HI and the grain yield.The yield of T3 was 9.2,35.7 and 20.1% higher than that of CK,T1 and T2 on average,respectively.The T3 treatment also increased the root bleeding sap intensity,the content of soluble sugar in the bleeding sap and post-silking N uptake and N accumulation in grain.Compared with CK,T1 and T2 treatments,the grain N accumulation in T3 increased by 13.1,40.9 and 25.2% on average,respectively.In addition,under the same source reduction treatment,the maize yield of HD was significantly higher than that of CD.Therefore,planting density should be increased in maize production for higher grain yield.Under HD,moderate decreasing leaf source improved photosynthetic performance and increased the post-silking dry matter accumulation and HI,and thus the grain yield.In addition,the improvement of photosynthetic performance improved the root function and promoted postsilking N uptake,which led to the increase of N accumulation in grain.

Integrating phosphorus management and cropping technology for sustainable maize production

Achieving high maize yields and efficient phosphorus(P)use with limited environmental impacts is one of the greatest challenges in sustainable maize production.Increasing plant density is considered an effective approach for achieving high maize yields.However,the low mobility of P in soils and the scarcity of natural P resources have hindered the development of methods that can simultaneously optimize P use and mitigate the P-related environmental footprint at high plant densities.In this study,meta-analysis and substance flow analysis were conducted to evaluate the effects of different types of mineral P fertilizer on maize yield at varying plant densities and assess the flow of P from rock phosphate mining to P fertilizer use for maize production in China.A significantly higher yield was obtained at higher plant densities than at lower plant densities.The application of single superphosphate,triple super-phosphate,and calcium magnesium phosphate at high plant densities resulted in higher yields and a smaller environmental footprint than the application of diammonium phosphate and monoammonium phosphate.Our scenario analyses suggest that combining the optimal P type and application rate with a high plant density could increase maize yield by 22%.Further,the P resource use efficiency throughout the P supply chain increased by 39%,whereas the P-related environmental footprint decreased by 33%.Thus,simultaneously optimizing the P type and application rate at high plant densities achieved multiple objectives during maize production,indicating that combining P management with cropping techniques is a practical approach to sustainable maize production.These findings offer strategic,synergistic options for achieving sustainable agricultural development.

Grain yield and N uptake of maize in response to increased plant density under reduced water and nitrogen supply conditions

The development of modern agriculture requires the reduction of water and chemical N fertilizer inputs.Increasing the planting density can maintain higher yields,but also consumes more of these restrictive resources.However,whether an increased maize density can compensate for the negative effects of reduced water and N supply on grain yield and N uptake in the arid irrigated areas remains unknown.This study is part of a long-term positioning trial that started in 2016.A split-split plot field experiment of maize was implemented in the arid irrigated area of northwestern China in 2020 to 2021.The treatments included two irrigation levels:local conventional irrigation reduced by 20%(W1,3,240 m^(3)ha^(-1))and local conventional irrigation(W2,4,050 m^(3)ha^(-1));two N application rates:local conventional N reduced by 25%(N1,270 kg ha^(-1))and local conventional N(360 kg ha^(-1));and three planting densities:local conventional density(D1,75,000 plants ha^(-1)),density increased by 30%(D2,97,500 plants ha-1),and density increased by 60%(D3,120,000 plants ha^(-1)).Our results showed that the grain yield and aboveground N accumulation of maize were lower under the reduced water and N inputs,but increasing the maize density by 30% can compensate for the reductions of grain yield and aboveground N accumulation caused by the reduced water and N supply.When water was reduced while the N application rate remained unchanged,increasing the planting density by 30% enhanced grain yield by 13.9% and aboveground N accumulation by 15.3%.Under reduced water and N inputs,increasing the maize density by 30% enhanced N uptake efficiency and N partial factor productivity,and it also compensated for the N harvest index and N metabolic related enzyme activities.Compared with W2N2D1,the N uptake efficiency and N partial factor productivity increased by 28.6 and 17.6%under W1N1D2.W1N2D2 had 8.4% higher N uptake efficiency and 13.9% higher N partial factor productivity than W2N2D1.W1N2D2 improved urease activity and nitrate reductase activity by 5.4% at the R2(blister)stage and 19.6% at the V6(6th leaf)stage,and increased net income and the benefit:cost ratio by 22.1 and 16.7%,respectively.W1N1D2 and W1N2D2 reduced the nitrate nitrogen and ammoniacal nitrogen contents at the R6 stage in the 40-100 cm soil layer,compared with W2N2D1.In summary,increasing the planting density by 30% can compensate for the loss of grain yield and aboveground N accumulation under reduced water and N inputs.Meanwhile,increasing the maize density by 30% improved grain yield and aboveground N accumulation when water was reduced by 20% while the N application rate remained constant in arid irrigation areas.

Cultivation of “Roxo de Valinhos” Fig Tree in Different Plant Densities for Production of Green Figs for Industry in the Region of Campo Das Vertentes-MG

The objective of this work was to study the effect of different planting densities on the development and production of “Roxo de Valinhos” green figs for industry, in the Campo das Vertentes-MG region. The experiment was installed at the Risoleta Neves Experimental Field—CERN/EPAMIG. The plants used were three years old and were arranged in three randomized blocks, subject to three different planting densities, with spacings ranging from 1 m (4000 plants·ha-1), 1.5 m (2666 plants·ha-1), and 2 m (2000 plants·ha-1) between plants in the planting line and 2.5 m between row for all planting densities. The average length of the branches (m), average number of fruits per branch, average number of fruits per plant, average weight of fruits, average yield per plant and the average yield per hectare (kg) were evaluated. It was verified that, there were no significant differences in the length of branch and in the average weight of fruit, in the three densities of fig tree planting. (4000 plants·ha-1), the average number of fruits per branch (7.5), per plant (55.87) and yield per plant (878.93 kg) were lower, however. The average yield per hectare (3515.73 kg) was higher than in other growing densities. It is concluded that, the higher density of plants (4000 plants·ha-1), provides the highest productivity per area, without damages to the quality of the fruits.

Improving grain yield, nitrogen use efficiency and radiation use efficiency by dense planting, with delayed and reduced nitrogen application, in double cropping rice in South China

Improving both grain yield and resource use efficiencies simultaneously is a major challenge in rice production.However,few studies have focused on integrating dense planting with delayed and reduced nitrogen application to enhance grain yield,nitrogen use efficiency (NUE) and radiation use efficiency (RUE) in rice (Oryza sativa L.) in the double rice cropping system in South China.A high-yielding indica hybrid rice cultivar (Yliangyou 143) was grown in field experiments in Guangxi,South China,with three cultivation managements:farmers’practice (FP),dense planting with equal N input and delayed N application (DPEN) and dense planting with reduced N input and delayed N application (DPRN).The grain yields of DPRN reached 10.6 and 9.78 t ha^(–1) in the early and late cropping seasons,respectively,which were significantly higher than the corresponding yields of FP by 23.9–29.9%.The grain yields in DPEN and DPRN were comparable.NUE in DPRN reached 65.2–72.9 kg kg^(–1),which was 61.2–74.1% higher than that in FP and 24.6–30.2% higher than that in DPEN.RUE in DPRN achieved 1.60–1.80 g MJ^(–1),which was 28.6–37.9% higher than that in FP.The productive tiller percentage in DPRN was 7.9–36.2% higher than that in DPEN.Increases in crop growth rate,leaf area duration,N uptake from panicle initiation to heading and enhancement of the apparent transformation ratio of dry weight from stems and leaf sheaths to panicles all contributed to higher grain yield and higher resource use efficiencies in DPRN.Correlation analysis revealed that the agronomic and physiological traits mentioned above were significantly and positively correlated with grain yield.Comparison trials carried out in Guangdong in 2018 and 2019 also showed that DPRN performed better than DPEN.We conclude that DPRN is a feasible approach for simultaneously increasing grain yield,NUE and RUE in the double rice cropping system in South China.

High nitrogen application rate and planting density reduce wheat grain yield by reducing filling rate of inferior grain in middle spikelets

Excessive use of nitrogen fertilizer and high planting density reduce grain weight in wheat.However,the effects of high nitrogen and planting density on the filling of grain located in different positions of the wheat spikelet are unknown.A two-year field experiment was conducted to investigate this question and the underlying mechanisms with respect to hormone and carbohydrate activity.Both high nitrogen application and planting density significantly increased spike density,while reducing kernel number per spike and 1000-kernel weight.However,the effects of high nitrogen and high plant density on kernel number per spike and 1000-kernel weight were different.The inhibitory effect of high nitrogen application and high planting density on kernel number per spike was achieved mainly by a reduction in kernel number per spikelet in the top and bottom spikelets.However,the decrease in 1000-kernel weight was contributed mainly by the reduced weight of grain in the middle spikelets.The grain-filling rate of inferior grain in the middle spikelets was significantly decreased under high nitrogen input and high planting density conditions,particularly during the early and middle grain-filling periods,leading to the suppression of grain filling and consequent decrease in grain weight.This effect resulted mainly from inhibited sucrose transport to and starch accumulation in inferior grain in the middle spikelets via reduction of the abscisic acid/ethylene ratio.This mechanism may explain how high nitrogen application and high planting density inhibit the grain filling of inferior wheat grain.

Planting density affected biomass and grain yield of maize for seed production in an arid region of Northwest China

Field experiments were conducted from 2012 to 2015 in an arid region of Northwest China to investigate the effects of planting density on plant growth, yield, and water use efficiency（WUE） of maize for seed production. Five planting densities of 6.75, 8.25, 9.75, 11.25 and 12.75 plants/m^2 were conducted in 2012, and a planting density of 14.25 plants/m^2 was added from 2013 to 2015. Through comparison with the Aqua Crop yield model, a modified model was developed to estimate the biomass accumulation and yield under different planting densities using adjustment coefficient for normalized biomass water productivity and harvest index. It was found that the modified yield model had a better performance and could generate results with higher determination coefficient and lower error. The results indicated that higher planting density increased the leaf area index and biomass accumulation, but decreased the biomass accumulation per plant. The total yield increased rapidly as planting density increased to 11.25 plants/m^2, but only a slight increase was observed when the density was greater than 11.25 plants/m^2. The WUE also reached the maximum when planting density was 11.25 plants/m^2, which was the recommended planting density of maize for seed production in Northwest China.

N, P and K use efficiency and maize yield responses to fertilization modes and densities

Optimal planting density and proper fertilization method are important factors to improve maize yield and nutrient utilization. A two-year(2016 and 2017) field experiment was conducted with three plant densities(6.0, 7.5 and 9.0 plants m^-2) and three fertilization modes(no fertilizer, 0 F;one-off application of slow-released fertilizer, SF;twice application of conventional fertilizer, CF). Results indicated that the grain yields and N, P and K use efficiencies under SF with the optimal planting density(7.5 plants m^-2) were the highest among all the treatments in 2016 and 2017. Compared with CF, SF could increase post-silking dry matter accumulation and promote N, P and K uptake at pre-and post-silking stages;this treatment increased grain N, P and K concentrations and resulted in high N, P and K use efficiencies. Nutrient(N, P and K) absorption efficiencies and partial productivity, and nutrient(N and P) recovery efficiency in SF treatment were significantly higher than those in CF treatments under the planting density of 7.5 plants m^-2. Under both SF and CF conditions, the grain yield, total N accumulation and nutrient use efficiencies initially increased, peaked at planting density of 7.5 plants m^-2, and then decreased with increasing plant density. Based on the yield and nutrient use efficiency in two years, plant density of 7.5 plants m^-2 with SF can improve both the grain yield and N, P and K use efficiency of spring maize in Jiangsu Province, China.

Multi-Location Investigation of Optimum Planting Density and Boll Distribution of High-Yielding Cotton (G.hirsutum L.) in Hubei Province,China

Cotton yield per unit ground area has stagnated for a dozen years in Hubei Province, China, although a series of new high- yielding varieties have been commercialized. A multi-location investigation was carried out in 2008 and 2009 in 13 counties to determine if increased planting population density （PPD） would break the stagnant yield. The results showed that significant differences among the fields existed in theoretical yield, PPD, and bolls per square meter （BPM）. The lowest yield of 1 641.1 kg ha-I was resulted from the lowest PPD of 1.7 plants m-2 and the lowest BPM of 71.8 bolls m-2, while the highest yield of 2 779.7 kg ha-~ was resulted from the highest PPD of 2.5 plants m-2, and the highest BPM of 129.4 bolls m-z. Plant mapping revealed that boll retention rate （BRR） was maintained over 30 or 40% for the first 17-18 fruiting branches （FBs） and decreased dramatically thereafter, rotten boll rate （RBR） decreased, but open boll rate （OBR） rose first and dropped later with rising FB from the bottom to the top. But BRR, RBR, and OBR were all dropped with the fruiting positions （FPs） extending outwards. The optimum range of plant density would be 2-3 plants m-2 and the proper individual plant structure would be 16-19 FBs with 5-7 FPs for cotton production in Hubei Province.

Root characteristics and yield of rice as affected by the cultivation pattern of strong seedlings with increased planting density and reduced nitrogen application

To address the relationships between the amount of nitrogen fertilizer application and the yield of double cropping rice systems,we investigated the effects of a cultivation pattern of strong seedlings with increased planting density and reduced nitrogen application(SDN)on the morphological and physiological characteristics of double cropping rice.Our results indicated that the effects of SDN on the morphological characteristics of the single plant roots of double cropping rice were not significant,but the morphological characteristics of the population roots were largely different.Specifically,SDN significantly increased the morphological indexes of the root population such as root fresh weight,root volume,root number,root length and root dry weight.The effects of SDN on the total root absorption areas and root active absorption areas of the single plants were non-significant,but it dramatically enhanced the total root absorption areas and root active absorption areas of the plant population during the tillering,heading and mature stages.In addition,SDN significantly increased the root bleeding intensity and elevated the soluble sugar and free amino acid contents of root bleeding sap.Compared to the traditional cultivation pattern(CK),SDN significantly increased root bleeding intensity at the heading stage by 4.37 and 8.90% for early and late rice,respectively.Meanwhile,SDN profoundly enhanced the soluble sugar contents of root bleeding sap by 12.85 and 10.41% for early and late rice,respectively.In addition,SDN also significantly enhanced free amino acid content of root bleeding sap by 43.25% for early rice and by 37.50% for late rice systems compared to CK.Furthermore,SDN increased the actual yield of double cropping rice mainly due to the higher effective panicle number and the larger seedsetting rate.The actual yields of early rice under SDN were higher than CK by 9.37 and 5.98% in 2016 and 2017,and the actual yields of late rice under SDN were higher than CK by 0.20 and 1.41% in 2016 and 2017,respectively.Correlation analysis indicated that the significant positive correlations were observed between the majority of the root indexes and the actual yield across the four different growth stages.

Reducing nitrogen application with dense planting increases nitrogen use efficiency by maintaining root growth in a double-rice cropping system

Rational nitrogen(N) application can greatly increase rice(Oryza sativa L.) yield. However, excessive N input can lead not only to low N use efficiency(NUE) but also to severe environmental pollution.Reducing N application rate with a higher planting density(RNHD) is recommended to maintain rice yield and improve NUE. The effects of RNHD on fertilizer N fate and rice root growth traits remain unclear. We accordingly conducted a two-year field experiment to investigate the influence of RNHD on rice yield, fertilizer 15N fate, and root growth in a double-rice cropping system in China. In comparison with the conventional practice of high N application with sparse planting, RNHD resulted in similar yield and biomass production as well as plant N uptake. RNHD increased agronomic NUEs by 23.3%–31.9%(P < 0.05) and N recovery efficiency by 17.4%–24.1%(P < 0.05). RNHD increased fertilizer 15N recovery rate by 14.5%–34.7%(P < 0.05), but reduced15 N retention rate by 9.2%–12.0%(P < 0.05). Although a reduced N rate led to significantly reduced root length, surface area, volume, and biomass, these root traits were significantly increased by higher planting density. RNHD did not affect these root morphological traits and reduced activities of nitrate reductase(NR) and glutamine synthetase(GS) only at tillering stage. Plant N uptake was significantly positively correlated with these root traits, but not correlated with NR and GS activities. Together, these findings show that reducing N application with dense planting can lead to high plant N uptake by maintaining rice root growth and thus increase NUE.

Mapping QTL for flowering time-related traits under three plant densities in maize

Flowering time is an indicator of adaptation in maize and a key trait for selection in breeding.The genetic basis of flowering time in maize,especially in response to plant density,remains unclear.The objective of this study was to identify maize quantitative trait loci(QTL)associated with flowering time-related traits that are stably expressed under several plant densities and show additive effects that vary with plant density.Three hundred recombinant inbred lines(RIL)derived from a cross between Ye 478 and Qi 319,together with their parents,were planted at three plant densities(90,000,120,000,and 150,000 plants ha^(-1))in four environments.The five traits investigated were days to tasseling(DTT),days to silking(DTS),days to pollen shed(DTP),interval between anthesis and silking(ASI),and interval between tasseling and anthesis(TAI).A high-resolution bin map was used for QTL mapping.In the RIL population,the DTT,DTS,and DTP values increased with plant density,whereas the ASI and TAI values showed negligible response to plant density.A total of 72 QTL were identified for flowering time-related traits,including 15 stably expressed across environments.Maize flowering time under different densities seems to be regulated by complex pathways rather than by several major genes or an independent pathway.The effects of some stable QTL,especially qDTT8-1 and qDTT10-4,varied with plant density.Fine mapping and cloning of these QTL will shed light on the mechanism of flowering time and assist in breeding earlymaturing maize inbred lines and hybrids.

Yield photosynthesis and leaf anatomy of maize in inter-and mono-cropping systems at varying plant densities

Increasing plant density can increase cereal crop yields. However, the physiological and anatomical mechanisms of grain yield increase at high plant densities in maize-based intercropping systems are not well understood. A two-year field experiment was conducted in 2018 and 2019 to investigate grain yield, photosynthetic characteristics, stomatal traits, and leaf anatomy of maize plants in an intercropping system with high plant densities. Two cropping patterns(monocropping and intercropping) and three plant densities(D1, 78,000 plants ha^(-1);D2, 103,500 plants ha^(-1);D3, 129,000 plants ha;were arranged in a randomized block design. Increasing maize plant density significantly increased maize yield, and intercropping gave a significant yield advantage over monocropping under the same plant density. Intercropping combined with high plant density increased the leaf area and SPAD value of maize,increasing the photosynthesis rates after the harvest of pea. At the twelfth leaf stage, the stomatal density and stomatal area of intercrops combined with medium plant density increased by respectively 10.5%and 18.4% relative to their values for the corresponding density of monocrops. Although leaf thickness of maize was reduced by increasing plant density, the chloroplast number and grana lamella number were higher in intercropping than in monocropping under different plant densities. These positive changes in leaf anatomy resulted in increased photosynthesis, suggesting a physiological basis for the increase in grain yield.

Evaluation of Plant Densities and Various Irrigation Regimes of Sorghum (Sorghum bicolor L.) under Low Water Supply

Drought stress, during growth season along with plant density, is an important problem that needs attention. In order to investigate the influence of both factors in increasing the water use efficiency, field experiments were laid out in split-plot design at Agriculture Research Station, Collage of Food and Agriculture Sciences, King Saud University, to investigate the effects of irrigation intervals viz., irrigation every (6, 9 and 12 days) under different plant densities i.e., (6, 8 and 10 plants/m2) on growth, yield and yield component parameters as well as grain quality of sorghum local variety (Gizani). Results revealed that almost all growth, yield and yield component parameters were significantly influenced by both factors as well as their interaction. Chemical composition of seeds, leaf proline content and WUE were also considered. Severe drought stress condition caused gradual decrease in most of the growth characters as compared to watered treatment and reflected in decreasing yield and yield component characters. Increasing plant densities led to raise biomass production and seed yield per unit area and not able to compensated the low number and weight of grains per panicle. Contrary, low plant density, under adequate irrigation conditions, can be compensated by a high number of grains per panicle and high weight of the grain. Maximum seed yield per hectare was recorded by the interactional effects of most watered treatments (irrigation every 6 days) and plant density of 10 plants per square meter.