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.

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.

Effects of Planting Density on Growth of New Clones in Populus tomentosa

Effects of seven planting densities on the growth and tree form of nine 5-year-old new clones in Populus tomentosa were studied. The plantations, arranged with completely random block design, were located in Wuzhi County, Henan Province. Results indicated that effects of planting density on the diameter at breast height (DBH), individual volume and growing stock increment of all new clones in P. tomentosa were significant at the 1% level of probability, effects of planting density on the tree height increment of new clones B2 and B31 and on the live branches height (LBH) increment of new clones B5 and B30 were significant at the 5% level of probability, while the interaction between planting density and clone was not significant at the 5% level of probability. It was concluded that the degree of differences among new clones within the same planting density was different with different planting densities and traits. For short rotation industrial timber, clones B1, B3, B4, B5, B7, B9, B31 were suitable with the density of 1 0002 500 trees per hectare, while for bigger diameter timber, clones B1, B3, B4, B7, B9, B31 could be used with the planting density of 660833 trees per hectare. Clonal repeatability was also different in different planting densities.

Genome-wide association study and metabolic pathway prediction of barrenness in maize as a response to high planting density

Increasing the planting density is one way to enhance grain production in maize.However,high planting density brings about growth and developmental defects such as barrenness,which is the major factor limiting grain yield.In this study,the barrenness was characterized in an association panel comprising 280 inbred lines under normal(67500 plants ha–1,ND)and high(120000 plants ha–1,HD)planting densities in 2017 and 2018.The population was genotyped using 776254 single nucleotide polymorphism(SNP)markers with criteria of minor allele frequency>5%and<20%missing data.A genome-wide association study(GWAS)was conducted for barrenness under ND and HD,as well as the barrenness ratio(HD/ND),by applying a Mixed Linear Model that controls both population structure and relative kinship(Q+K).In total,20 SNPs located in nine genes were significantly(P<6.44×10–8)associated with barrenness under the different planting densities.Among them,seven SNPs for barrenness at ND and HD were located in two genes,four of which were common under both ND and HD.In addition,13 SNPs for the barrenness ratio were located in seven genes.A complementary pathway analysis indicated that the metabolic pathways of amino acids,such as glutamate and arginine,and the mitogen-activated protein kinase(MAPK)signaling pathway might play important roles in tolerance to high planting density.These results provide insights into the genetic basis of high planting density tolerance and will facilitate high yield maize breeding.

Evidence of arrested silk growth in maize at high planting density using phenotypic and transcriptional analyses

Increasing the planting density is an effective way to increase the yield of maize(Zea mays L.),although it can also aggravate ovary apical abortion-induced bald tips of the ears,which might,in turn,reduce the yield.While the mechanism underlying the regulation of drought-related abortion in maize is well established,high planting density-related abortion in maize remains poorly understood.Therefore,the present study was designed to investigate the mechanism underlying the ovary apical abortion response to high density.This was achieved by evaluating the effects of four different plant densities(60000 plants ha^(–1)(60 k),90 k,120 k,and 150 k)on plant traits related to plant architecture,the plant ear,flowering time,and silk development in two inbred lines(Zheng58 and PH4CV)and two hybrid lines(Zhengdan958 and Xianyu335).The phenotypes of both inbred and hybrid plants were observed under different planting density treatments,and the high planting density was found to increase the phenotypic performance values of the evaluated traits.The anthesis–silking interval(ASI)was extended,and the amount of the silk extruded from husks was reduced upon increasing the planting density.Delayed silk emergence resulted in asynchronous flowering and ear bald tips.Observations of the silk cells revealed that the silk cells became smaller as planting density increased.The changes in transcript abundances in the silks involved the genes associated with expansive growth rather than carbon metabolism.These findings further our understanding of silk growth regulation under high planting density and provide a theoretical basis for further research on improving high planting density breeding in maize.

Effects of Planting Density and Cutting Time on Hay Yield and Nutritional Value of Forage Soybean HN389

Forage soybean is an important source of high protein forage.Variety screening and breeding not only can solve the adjustment of agricultural planting structure,but also can provide a large amount of high-protein forage material,and effectively solve the problem of a serious shortage of high-protein forage in herbivorous animal husbandry in China.In this study,the feeding-type soybean strain HN389 was selected as experimental material,with three planting densities of 270000,405000 and 540000 plants•hm^(-2) and three cutting periods of the initial pod stage(R1),the initial grain stage(R2)and the early mature stage(R3)were set to determine the yield and feeding quality,in order to obtain the best planting density and harvest time of the variety.The results showed that in forage soybean strain HN389 at the R1 and R2 stages,plant height increased with increasing planting densities,while fresh and dry weight per plant decreased with increasing planting densities,and there was no significant difference at the R3 stage.The yield of hay at the R1,R2 and R3 stages increased firstly and then decreased with the increase of planting densities,and the yield per hectare was R3>R2>R1.The order of contents of crude protein(CP),neutral detergent fibers(NDF)and acid detergent fiber(ADF)in feeding quality of HN389 were R2>R1>R3,and ether extract(EE)content order was R3>R1>R2,and there was no significant difference among different groups.Two principal components were extracted from five forage indexes including CP,NDF,ADF,EE and fresh grass yield by principal component analysis.The cumulative contribution rate of principal components 1 and 2 was 90.053%,and their characteristic values were 3.617 and 0.885,respectively.After a comprehensive evaluation,harvested at the R3 stage and the density was 405000 plants•hm^(-2),HN389 had the highest comprehensive score of 0.344,yield of 38035.53 kg•hm^(-2),CP,NDF,ADF and EE contents of 17.61%,17.61%,21.54%and 3.81%,respectively.

Effect of Planting Density on Physiological Indexes, Agronomic Traits and Yield of Buckwheat ( Fagopyrum esculentum Moench.)

Ningqiao 1 was selected as the material to study the effects of planting density on physiological indices,agronomic traits and yield of buckwheat.The results showed that high density resulted in decreases of chlorophyll content,soluble protein content and activity of SOD,POD and CAT,and acceleration of MDA accumulation under drought conditions.Low density could effectively improve the grain number per plant,grain weight per plant,1000-grain weight and yield in drought conditions.

Effect of Fertilizing Amount and Planting Density on Yield and Qual-ity of Strong-gluten Wheat Taishan 27

To get the cultivation pattern featured by improved varieties and fine methods for strong-gluten and high-yielding wheat variety Taishan 27,this paper used Taishan 27 as material to study the effect of fertilizing amount and planting density on yield and quality of material.The results showed that Taishan 27 had high yield under fertilizing amount of 225 kg/ha pure nitrogen and planting density of 240 × 104-300× 10~4/ha; the yield was lowest under fertilizing amount of 300 kg/ha pure nitrogen and planting density of 360 × 10~4/ha. The suitable planting density for Taishan 27 was 240 × 104-300 × 10~4/ha,and the fertilizing amount of nitrogen should be based on different soil fertility conditions to avoid water and fertilizer stress and improve yield.

Effects of Planting Density of Quinoa on Agronomic Characters and Yield in Chengde

[Objectives]To study the optimum sowing density of quinoa in Chengde region.[Methods]Yanli No.2 cultivated by Institute of Millet Crops,Hebei Academy of Agriculture and Forestry Sciences was taken as test material.In Chengde region,single-factor density test design was used to study the effects of sowing on agronomic characters and yield of quinoa.[Results]Quinoa had the highest comprehensive yield when row spacing was 30 cm and plant spacing was 25 cm.[Conclusions]The research could provide theoretical basis for quinoa planting in Chengde region.

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.

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.

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.

Responses of radial growth, wood density and fiber traits to planting space in poplar plantations at a lowland site

Poplar is raw material for various panel, paper and fiber products. The 12 sample trees of clone Nanlin-895 from four spacings were destructively harvested after thirteen growing seasons to assess the influence of spacing on radial growth and wood properties. Spacing significantly affected tree-ring width and wood basic density (p < 0.05) but not fiber traits. The highest diameter and wood basic density at breast height (1.3 m) was in 6 m × 6 m and 3 m × 8 m spacings, respectively. However, no significant differences in tree-ring width, wood basic density and fiber traits were observed among the four sampling directions in discs taken at 1.3 m for each spacing. Growth rings from the pith and tree heights had significant effects on wood basic density and fiber anatomical characteristics, highlighting obvious temporal-spatial variations. Pearson correlation analysis showed a significantly negative relationship of tree-ring width to wood basic density, fiber length and fiber width, but a significantly positive relationship to hemicellulose. There was no relationship with cellulose and lignin contents. Based on a comprehensive assessment by the TOPSIS method, the 6 m × 6 m spacing is recommended for producing wood fiber at similar sites in the future.

Nitrogen management improves lodging resistance and production in maize(Zea mays L.)at a high plant density

Lodging in maize leads to yield losses worldwide.In this study,we determined the effects of traditional and optimized nitrogen management strategies on culm morphological characteristics,culm mechanical strength,lignin content,root growth,lodging percentage and production in maize at a high plant density.We compared a traditional nitrogen(N)application rate of 300 kg ha–1(R)and an optimized N application rate of 225 kg ha^(–1)(O)under four N application modes:50%of N applied at sowing and 50%at the 10th-leaf stage(N1);100%of N applied at sowing(N2);40%of N applied at sowing,40%at the 10th-leaf stage and 20%at tasseling stage(N3);and 30%of N applied at sowing,30%at the 10th-leaf stage,20%at the tasseling stage,and 20%at the silking stage(N4).The optimized N rate(225 kg ha^(–1))significantly reduced internode lengths,plant height,ear height,center of gravity height and lodging percentage.The optimized N rate significantly increased internode diameters,filling degrees,culm mechanical strength,root growth and lignin content.The application of N in four split doses(N4)significantly improved culm morphological characteristics,culm mechanical strength,lignin content,and root growth,while it reduced internode lengths,plant height,ear height,center of gravity height and lodging percentage.Internode diameters,filling degrees,culm mechanical strength,lignin content,number and diameter of brace roots,root volume,root dry weight,bleeding safe and grain yield were significantly negatively correlated with plant height,ear height,center of gravity height,internode lengths and lodging percentage.In conclusion,treatment ON4 significantly reduced the lodging percentage by improving the culm morphological characteristics,culm mechanical strength,lignin content,and root growth,so it improved the production of the maize crop at a high plant density.

Effects of mepiquat chloride and plant population density on leaf photosynthesis and carbohydrate metabolism in upland cotton

Background Mepiquat chloride(MC)application and plant population density(PPD)increasing are required for modern cotton production.However,their interactive effects on leaf physiology and carbohydrate metabolism remain obscure.This study aimed to examine whether and how MC and PPD affect the leaf morpho-physiological characteristics,and thus final cotton yield.PPD of three levels(D1:2.25 plants·m^(-2),D2:4.5 plants·m^(-2),and D3:6.75 plants·m^(-2))and MC dosage of two levels(MC0:0 g·ha^(-2),MC1:82.5 g·ha^(-2))were combined to create six treatments.The dynamics of nonstructual carbohydrate concentration,carbon metabolism-related enzyme activity,and photosynthetic attributes in cotton leaves were examined during reproductive growth in 2019 and 2020.Results Among six treatments,the high PPD of 6.75 plants·m^(-2)combined with MC application(MC1D3)exhibited the greatest seed cotton yield and biological yield.The sucrose,hexose,starch,and total nonstructural carbohydrate(TNC)concentrations peaked at the first flowering(FF)stage and then declined to a minimum at the first boll opening(FBO)stage.Compared with other treatments,MC1D3 improved starch and TNC concentration by 5.4%~88.4%,7.8%~52.0% in 2019,and by 14.6%~55.9%,13.5%~39.7% in 2020 at the FF stage,respectively.Additionally,MC1D3 produced higher transformation rates of starch and TNC from the FF to FBO stages,indicating greater carbon production and utilization efficiency.MC1D3 displayed the maximal specific leaf weight(SLW)at the FBO stage,and the highest chlorophyll a(Chl a),Chl b,and Chl a+b concentration at the mid-late growth phase in both years.The Rubisco activity with MC1D3 was 2.6%~53.2% higher at the flowering and boll setting stages in both years,and 2.4%~52.7% higher at the FBO stage in 2020 than those in other treatments.These results provided a explanation of higher leaf senescence-resistant ability in MC1D3.Conclusion Increasing PPD coupled with MC application improves cotton yield by enhancing leaf carbohydrate production and utilization efficiency and delaying leaf senescence.

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.

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.

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.

Effect of Plant Density on Modern Soybean Cultivars Released from Ohio and Liaoning

Seeding rate is an important management practice for soybean production.Chinese and U.S.soybean growers use different seeding rates,and breeders in the two countries have developed cultivars adapted to respective plant densities.The objective of this study was to compare the effect of plant density on cultivars recently released in different breeding programs,using four cultivars developed in Liaoning,China and four in Ohio,USA.We used 3 plant density treatments(7.5,15.0,22.5 x 104 plants/hm2) and assessed yield and agronomic traits from 2004 to 2006 in Liaoning.There was no significant effect of plant density on yield for either group of the cultivars.The average yield of Ohio cultivars was higher than that of Liaoning cultivars,and there was no significant interaction between plant density and cultivar for all the assessed traits.The plant height of Liaoning cultivars was significantly higher than that of Ohio cultivars,and there was a significant effect of plant density on plant height.The average branch number of Ohio cultivars was larger than that of Liaoning cultivars;higher plant density reduced the branch number per plant greatly.Plant density had a signifi-cant effect on the node number and internode length,Liaoning cultivars generally had longer internode length.Plant density had a significant effect on seed yield:stem ratio,as the plant density increased the seed yield:stem ratio decreased for both groups of cultivars.However,100-seed weight was not affected by plant 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.