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.

Salinity Stress Deteriorates Grain Yield and Increases 2-Acetyl-1-Pyrroline Content in Rice

Salinity stress greatly impacts rice grain yield and quality, as well as the 2-acetyl-1-pyrroline(2-AP) content in grains. The present study was conducted with Nanjing 9108(NJ9108, conventional japonica rice) and Wenliangyou 669(WLY669, indica hybrid rice) in the fields with non-salinity(NS), low salinity(LS), and high salinity(HS) stresses in 2021 and 2022.

J-family genes redundantly regulate flowering time and increase yield in soybean

Soybean(Glycine max)is a short-day crop whose flowering time is regulated by photoperiod.The longjuvenile trait extends its vegetative phase and increases yield under short-day conditions.Natural variation in J,the major locus controlling this trait,modulates flowering time.We report that the three J-family genes influence soybean flowering time,with the triple mutant Guangzhou Mammoth-2 flowering late under short days by inhibiting transcription of E1-family genes.J-family genes offer promising allelic combinations for breeding.

Magnesium fertilizer application increases peanut growth and pod yield under reduced nitrogen application in southern China

This study investigated the effect of magnesium application on peanut growth and yield under two nitrogen(N)application rates in acidic soil in southern China.The chlorophyll content,net photosynthetic rate and dry matter accumulation of the N-sensitive cultivar decreased under reduced N treatments,whereas no effect was observed on the relevant indicators in the N-insensitive variety GH1026.Mg application increased the net photosynthetic rate by increasing the expression of genes involved in chlorophyll synthesis and Rubisco activity in the leaves during the pegging stage under 50%N treatment,while no effect on the net photosynthetic rate was observed under the 100%N treatment.The rate of dry matter accumulation at the early growth stage,total dry matter accumulation and pod yield at harvest increased after Mg application under 50%N treatment by increasing the transportation of assimilates from stems and leaves to pods in both peanut varieties,whereas no effect was found under 100%N treatment.Moreover,Mg application increased the NUE under 50%N treatment.No improvement of NUE in either peanut variety was found under 100%N treatment,while Mg application under the 50%N treatment can obtain a higher economic benefit than the 100%N treatment.In acidic soil,application of 307.5 kg ha^(-1)of Mg sulfate fertilizer under 50%reduced nitrogen application is a suitable fertilizer management measure for improving carbon assimilation,NUE and achieve high peanut yields in southern China.

Night warming increases wheat yield by improving pre-anthesis plant growth and post-anthesis grain starch biosynthesis

Global climate change is characterized by asymmetric warming,i.e.,greater temperature increases in winter,spring,and nighttime than in summer,autumn,and daytime.Field experiments were conducted using four wheat cultivars,namely‘Yangmai 18’(YM18),‘Sumai 188’(SM188),‘Yannong 19’(YN19),and‘Annong 0711’(AN0711),in the two growing seasons of 2019-2020 and 2020-2021,with passive night warming during different periods in the early growth stage.The treatments were night warming during the tillering-jointing(NW_(T-J)),jointing-booting(NWJ-B),and booting-anthesis(NWB-A)stages,with ambient temperature(NN)as the control.The effects of night warming during different stages on wheat yield formation were investigated by determining the characteristics of dry matter accumulation and translocation,as well as sucrose and starch accumulation in wheat grains.The wheat yields of all four cultivars were significantly higher in NW_(T-J)than in NN in the 2-year experiment.The yield increases of semi-winter cultivars YN19 and AN0711 were greater than those of spring cultivars YM18 and SM188.Treatment NW_(T-J)increased wheat yield mainly by increasing the 1,000-grain weight and the number of fertile spikelets,and it increased dry matter accumulation in various organs of wheat at the anthesis and maturity stages by increasing the growth rate at the vegetative growth stage.The flag leaf and spike showed the largest increases in dry matter accumulation.NW_(T-J)also increased the grain sucrose and starch contents in the early and middle grain-filling stages,promoting yield formation.Overall,night warming between the tillering and jointing stages increased the pre-anthesis growth rate,and thus,wheat dry matter production,which contributed to an increase in wheat yield.

Optimized tillage methods increase mechanically transplanted rice yield and reduce the greenhouse gas emissions

Biaxia lrotary tillage in dryland(DBRT)can complete biaxial rotary tillage with straw incorporation,secondary suppression,and ditching,and it has been previously studied in direct-seeded rice and wheat.However,the effects of DBRT on the mechanically transplanted rice yield and greenhouse gas emissions remain unclear.To evaluate the effects of DBRT on improving the food security of mechanically transplanted rice and reducing the greenhouse gas emissions,we conducted an experiment for two years with wheat straw incorporation.Three tillage methods were set up:DBRT,uniaxial rotary tillage in dryland and paddy(DPURT),and uniaxial rotary tillage in paddy(PURT).The results showed that compared with DPURT and PURT,DBRT increased the yield of machine-transplanted rice by 7.5-11.0%and 13.3-26.7%,respectively,while the seasonal cumulative CH_(4) emissions were reduced by 13.9-21.2%and 30.2-37.0%,respectively,and the seasonal cumulative N_(2)O emissions were increased by 13.5-28.6%and 50.0-73.1%,respectively.Consequently,DBRT reduced the global warming potential by 10.7-15.5%and 23.7-28.6%,respectively,andtheyield-scaledglobalwarmingpotentialby18.2-21.8%and36.4-39.3%,respectively,compared to DPURT and PURT.These results were mainly related to the fact that DBRT significantly reduced soil bulk density and increased soil redox potential(Eh).Therefore,implementing DBRT in machine-transplanted rice fields is feasible,which cannot only increase the rice yield,but also reduce the greenhouse gas emissions.

Discussion on Green Development of Fenlong for Yield Increase, Quality Enhancing, Water Retaining and Multiple Use of Natural Resources

Fenlong green ecological agriculture technology （Fenlong technology）, a new smash ridging farming method developed by Guangxi Academy of Agdcultural Sciences, has been elected as the recommended cultivation technique by the Ministry of Agriculture of China. It replaces the traditional plowshare with spiral drill, and its tilth depth is twice deeper than that by tractor tilthing. It also extends soil nutrient, moisture, oxygen and microorganism, the so-called ＂Four pools＂. Soil nutrient, oxygen, microorganism, light and rainfall use ratio is increased by 10%-100%, creating a platform for natural increase of more than 10% of crop yield. Its application to over 20 kinds of crops in 21 provinces has proved that the yield increases 10-30% with quality enhancing 5% and double water retaining capacity but no more input. When the application area of Fenlong could reach 67 million hm2, the amount of fertilizer can be reduced by 40-50 billion kg, saving 120-150 billion Yuan. In this paper, we put forward the strategy of ＂4＋1＂ （arable, saline-alkali soil, grasslands, Sponge City ＋ rivers） green development in China, and deepened the Fenlong cultivated tilled layer from 16.5 cm to 35 cm for 67 million hm2 arable land, ridged 13.3 million hm2 of saline-alkali soil for 35 cm, and also 35 cm for 67 million hm2 degraded steppe, which could have the following 3 effects： first, the 147 million hm2 of land with Fenlong cultivation could increase loosing soil to 315.491 billion m3, in＊ creasing by 159.26% for 120 million hm2 of arable land with the average tilled layer of 16.5 cm, which has loosing soil of only 198.1 billion m3, that is, the space of the land increases 1.6 times. Second, every hectare of plowland could store up to 450 m3/hm2 of natural rainfall, and the unused 60 m3 of saline-alkali soil and grasslands could store water of 102 billion m3, showing an increase of over 88.89% for the current plowland storage of 54 billion m3 at now, that is, double the natural rainfall storage capacity. Third, the two multiple increase of natural resources application can bring trillions of resource activation, environmental cleaning, food security, citizens, health, economic, ecological and social benefits, and makes the Chinese nation move forward in green development. Its application in ＂big scientific research＂ and ＂One Belt And One Road＂ will contribute Chinese strength to the world.

The Salt Reduction and Yield Increase Effects of Smashing Ridging Transforming Saline-alkali Land and Its Development Prospects

Using smashing ridging tillage machine and smashing ridging technology invented by the authors, transformation test of saline-alkali land by smashing ridging was conducted respectively in Xinjiang and Shaanxi during 2015 -2016. The results showed, in severe saline-alkali soil of Xin-jiang ,after growing cotton by smashing ridging, total salt in soil decreased by 31.31 %, cotton production increased by 48.80%, and salinity level declined from severe to moderate; in mild saline-alkali soil of Shaanxi, after growing summer corn by smashing ridging, total salt in soil decreased by 42.37%, corn yield increased by 34.83%, salinity degree changed from mild desalination to normal farmland ; in Ningxia, Inner Mongolia 7 Gansu ,Jilin, Henan, Hebei, and so on, smashing ridging tillage practice in different types of saline-alkali land was conducted ; according to the salt reduction and yield increase effects of saline-alkali land after smashing ridging, the development prospect of smashing ridging technique in improvement and application of saline-alkali land was proposed.

Slight shading after anthesis increases photosynthetic productivity and grain yield of winter wheat (Triticum aestivum L.) due to the delaying of leaf senescence

The solar radiation intensity and duration are continuously decreasing in the major wheat planting area of China. As a con- sequence, leaf senescence, photosynthesis, grain filling and thus wheat yield shall be affected by light deficiency. Therefore, two winter wheat （Triticum aestivum L.） cultivars, Tainong 18 （a large-spike cultivar） and Ji＇nan 17 （a multiple-spike cultivar）, were subjected to shading during anthesis and maturity under field condition in 2010-2011 and 2011-2012. Under the slight shading treatment （$1,88% of full sunshine）, leaf senescence was delayed, net photosynthesis rate （Po） and canopy apparent photosynthesis rate （CAP） were improved, and thus thousand-kernel weight （TKW） and grain yield were higher as compared with the control. However, mid and severe shading （S2 andS3, 67 and 35% of full sunshine, respectively） led to negative effects on these traits substantially. Moreover, superoxide dismutase （SOD）, peroxidase （POD） and cat- alase （CAT） activities in flag leaf were significantly greater under slight shading than those in other treatments, while the malondialdehyde （MDA） content was less than that under other treatments. In addition, the multiple-spike cultivar is more tolerant to shading than large-spike cultivar. In conclusion, slight shading after anthesis delayed leaf senescence, enhanced photosynthesis and grain filling, and thus resulted in higher grain yield.

Long-term inorganic plus organic fertilization increases yield and yield stability of winter wheat

An understanding of wheat yield and yield stability response to fertilization is important for sustainable wheat production. A 36-year long-term fertilization experiment was employed to evaluate the yield and yield stability of winter wheat. Five fertilization regimes were compared,including(1) CK, no fertilizer;(2) NPK, inorganic fertilizer only;(3) O, organic fertilizer only;(4)NPKO, 50% of NPK plus 50% of O, and(5) HNPKO, 80% of NPK plus 80% of O. The greatest yield increase was recorded in HNPKO, followed by NPKO, with O producing the lowest mean yield increase. Over the 36 years, the rate of wheat yield increase in fertilized plots ranged from95.31 kg ha-1 year-1 in the HNPKO to 138.65 kg ha-1 year-1 in the O. Yield stability analysis using the additive main effects and multiplicative interactions(AMMI) method assigned 62.3%, 26.3%,and 11.4% of sums of squares to fertilization effect, environmental effect, and fertilization ×environment interaction effect, respectively. The combination of inorganic and organic fertilization(NPKO and HNPKO) appeared to produce more stable yields than O or NPK, with lower coefficients of variation and AMMI stability value. However, wheat grown with O seemed to be the most susceptible to climate change and the least productive among the fertilized plots.Significant correlations of grain yield with soil properties and with mean air temperature were observed. These findings suggest that inorganic + organic fertilizer can increase wheat yield and its stability by improvement in soil fertility and reduction in variability to climate change.

Delayed sowing can increase lodging resistance while maintaining grain yield and nitrogen use efficiency in winter wheat

Lodging resistance of winter wheat(Trnticum aestivum L.) can be increased by late sowing.However, whether grain yield and nitrogen use efficiency(NUE) can be maintained with delayed sowing remains unknown. During the 2013-2014 and 2014-2015 growing seasons, two winter wheat cultivars were sown on three dates(early sowing on October 1, normal so,wing on October8, and late sowing on October 15) to investigate the responses of lodging resistance, grain yield,and NUE to sowing date. No significant differences in lodging resistance, grain yield, or NUE between early and normal sowing were observed. Averaging over the two cultivars and years,postponing the sowing date significantly increased lodging resistance by 53.6% and 49.6%compared with that following early and normal sowing, respectively. Lodging resistance was improved mainly through a reduction in the culm height at the center of gravity and an increase in the tensile strength of the base internode. Late sowing resulted in similar grain yield as well as kernel weight and number of kernels per square meter, compared to early and normal sowing.Averaging over the two cultivars and years, delayed sowing resulted in a reduction in nitrogen uptake efficiency(UPE) by 11.0% and 9.9% compared to early and normal sowing, respectively,owing to reduced root length density and dry matter accumulation before anthesis. An average increase in nitrogen utilization efficiency(UTE) of 12.9% and 11.2% compared to early and normal sowing, respectively, was observed with late sowing owing to a reduction in the grain nitrogen concentration. The increase in UTE offset the reduction in UPE, resulting in equal NUEs among all sowing dates. Thus, sowing later than normal could increase lodging resistance while maintaining grain yield and NUE.

Increased plant density and reduced N rate lead to more grain yield and higher resource utilization in summer maize

Planting at an optimum density and supplying adequate nitrogen（N） to achieve higher yields is a common practice in crop production, especially for maize（Zea mays L.）; however, excessive N fertilizer supply in maize production results in reduced N use efficiency（NUE） and severe negative impacts on the environment. This research was conducted to determine the effects of increased plant density and reduced N rate on grain yield, total N uptake, NUE, leaf area index（LAI）, intercepted photosynthetically active radiation（IPAR）, and resource use efficiency in maize. Field experiments were conducted using a popular maize hybrid Zhengdan 958（ZD958） under different combinations of plant densities and N rates to determine an effective approach for maize production with high yield and high resource use efficiency. Increasing plant density was clearly able to promote N absorption and LAI during the entire growth stage, which allowed high total N uptake and interception of radiation to achieve high dry matter accumulation（DMA）, grain yield, NUE, and radiation use efficiency（RUE）. However, with an increase in plant density, the demand of N increased along with grain yield. Increasing N rate can significantly increase the DMA, grain yield, LAI, IPAR, and RUE. However, this increase was non-linear and due to the input of too much N fertilizers, the efficiency of N use at NCK（320 kg ha^（–1）） was low. An appropriate reduction in N rate can therefore lead to higher NUE despite a slight loss in grain production. Taking into account both the need for high grain yield and resource use efficiency, a 30% reduction in N supply, and an increase in plant density of 3 plants m^（–2）, compared to LD（5.25 plants m^（–2））, would lead to an optimal balance between yield and resource use efficiency.

Single-seed sowing increased pod yield at a reduced seeding rate by improving root physiological state of Arachis hypogaea

Double-seed sowing(two seeds per hole)is the dominant pattern of peanut sowing in China,but within-hole plant competition usually limits their growth and yield formation.Besides,the traditional double-seed sowing method does not facilitate mechanization during sowing.The objective of this study was to determine if single-seed sowing at a proper seeding rate yielded better than traditional double-seed sowing pattern and the differences of physiological metabolism of roots.A field experiment was conducted in two consecutive years to compare pod yields of single-seed sowing at 180000(S180),225000(S225),and 270000 seeds ha^-1(S270)with that of double-seed sowing at 270000 seeds ha^-1(D270)using a completely randomized block design with four replications.And the root bleeding sap rate,nutrient content,and the main hormone contents in root bleeding sap were also comparatively investigated.Although the pod yields of single-seed sowing at the three densities were higher than that of traditional double-seed sowing(D270),S225 yielded better than the other two single-seed sowing treatments(S180 and S270).The increased pod yield in single-seed sowing at 225000 seeds ha^-1 was mainly due to the higher pod dry weight per plant and harvest index.The improved pod dry weight and shoot growth had closely relationship with the enhanced root physiological traits such as the increased root bleeding sap rate,content of free amino acids,soluble sugars,K^+,Mg^2+,Zn^2+,and Ca^2+of the individual plant root.The improved activity of root reductive,nitrate reductase(NR)and ATPase and higher zeatin and zeatin riboside(Z+ZR)content of root bleeding sap were alsocrucial to the pod and shoot growth of peanut.Single-seed sowing at a moderate seeding rate(S225)is a potential practice to increase pod yield and to save seed cost.

Moderate wetting and drying increases rice yield and reduces water use, grain arsenic level, and methane emission

To meet the major challenge of increasing rice production to feed a growing population under increasing water scarcity,many water-saving regimes have been introduced in irrigated rice,such as an aerobic rice system,non-flooded mulching cultivation,and alternate wetting and drying(AWD).These regimes could substantially enhance water use efficiency(WUE) by reducing irrigation water.However,such enhancements greatly compromise grain yield.Recent work has shown that moderate AWD,in which photosynthesis is not severely inhibited and plants can rehydrate overnight during the soil drying period,or plants are rewatered at a soil water potential of-10 to-15 k Pa,or midday leaf potential is approximately-0.60 to-0.80 MPa,or the water table is maintained at 10 to 15 cm below the soil surface,could increase not only WUE but also grain yield.Increases in grain yield WUE under moderate AWD are due mainly to reduced redundant vegetative growth;improved canopy structure and root growth;elevated hormonal levels,in particular increases in abscisic acid levels during soil drying and cytokinin levels during rewatering;and enhanced carbon remobilization from vegetative tissues to grain.Moderate AWD could also improve rice quality,including reductions in grain arsenic accumulation,and reduce methane emissions from paddies.Adoption of moderate AWD with an appropriate nitrogen application rate may exert a synergistic effect on grain yield and result in higher WUE and nitrogen use efficiency.Further research is needed to understand root–soil interaction and evaluate the long-term effects of moderate AWD on sustainable agriculture.

Response of yield increase for dryland winter wheat to tillage practice during summer fallow and sowing method in the Loess Plateau of China

Soil moisture is the most critical limiting factor impacting yields of dryland winter wheat(Triticum aestivum L.) and it is strongly affected by tillage practice and sowing methods. This study was to assess the link between sowing method and tillage practice during summer fallow and their subsequent effect on soil moisture and grain yield. Furthermore, we sought to identify a more appropriate farming management practice for winter wheat production in Loess Plateau region of China. The experiment was conducted from 2011 to 2013, using a two-factor split plot design, including subsoiling(SS) or no tillage(NT) during summer fallow for main plots, and conventional drill sowing(DS) or plastic film drill sowing(FM) for subplots. Results showed that the maximum soil water storage(SWS) was under SS×FM treatment with values of 649.1 mm(2011–2012) and 499.4 mm(2012–2013). The SWS during the 2011–2012 growing season were 149.7 mm higher than that in the 2012–2013 growing season. And adoption of SS×FM significantly increased precipitation use efficiency(PUE) and water use efficiency(WUE) compared to other treatments for both seasons. Moreover, adoption of SS×FM significantly increased yield by 13.1, 14.4, 47.3% and 25.9, 39.1, 35.7% than other three treatments during the two growing seasons, respectively. In summary, combining subsoiling during summer fallow with plastic film drill sowing(SS×FM) increased SWS at sowing and effectively improved WUE, thus representing a feasible technology to improve grain yield of dryland winter wheat in the Loess Plateau of China.

Timing and splitting of nitrogen fertilizer supply to increase crop yield and efficiency of nitrogen utilization in a wheat–peanut relay intercropping system in China

Agronomically optimizing the timing and rates of nitrogen(N) fertilizer application can increase crop yield and decrease N loss to the environment. Wheat(Triticum aestivum L.)–peanut(Arachis hypogaea L.) relay intercropping systems are a mainstay of economic and food security in China. We performed a field experiment to investigate the effects of N fertilizer on N recovery efficiency, crop yield, and N loss rate in wheat–peanut relay intercropping systems in the Huang-Huai-Hai Plain, China during 2015–2017. The N was applied on the day before sowing, the jointing stage(G30) or the booting stage(G40) of winter wheat, and the anthesis stage(R1) of peanut in the following percentage splits: 50-50-0-0(N1), 35-35-0-30(N2), and 35-0-35-30(N3), using 300 kg N ha-1, with 0 kg N ha-1(N0) as control. ^(15)N-labeled(20.14 atom %) urea was used to trace the fate of N in microplots. The yields of wheat and peanut increased by 12.4% and 15.4% under the N2 and N3 treatments, relative to those under the N1 treatment. The ^(15)N recovery efficiencies( ^(15)NRE) were 64.9% and 58.1% for treatments N2 and N3, significantly greater than that for the N1 treatment(45.3%). The potential N loss rates for the treatments N2 and N3 were23.7% and 7.0%, significantly lower than that for treatment N1(30.1%). Withholding N supply until the booting stage(N3) did not reduce the wheat grain yield; however, it increased the N content derived from ^(15)N-labeled urea in peanuts, promoted the distribution of ^(15)N to pods, and ultimately increased pod yields in comparison with those obtained by topdressing N at jointing stage(N2). In comparison with N2, the N uptake and N recovery efficiency(NRE) of N3 was increased by 12.0% and 24.1%,respectively, while the apparent N loss decreased by 16.7%. In conclusion, applying N fertilizer with three splits and delaying topdressing fertilization until G40 of winter wheat increased total grain yields and NRE and reduced N loss. This practice could be an environment-friendly N management strategy for wheat–peanut relay intercropping systems in China.

Integrated agronomic practice increases maize grain yield and nitrogen use efficiency under various soil fertility conditions

Crop yield potential can be increased through the use of appropriate agronomic practices. Integrated agronomic practice (IAP) is an effective way to increase maize (Zea mays L.) grain yield and nitrogen use efficiency (NUE);however, the physiological processes associated with gains in yield potential obtained from IAP, particularly the different under various soil fertility conditions, remain poorly understood. An IAP strategy including optimal planting density, split fertilizer application, and subsoiling tillage was evaluated over two growing seasons to determine whether the effects of IAP on maize yield and NUE differ under different levels of soil fertility. Compared to farmers' practices (FP), IAP increased maize grain yield in 2013 and 2014 by 25% and 28%, respectively, in low soil fertility (LSF) fields and by 36% and 37%, respectively, in high soil fertility (HSF) fields. The large yield gap was attributed mainly to greater dry matter (DM) and N accumulation with IAP than with FP owing to increased leaf area index (LAI) and DM accumulation rate, which were promoted by greater soil mineral N content (Nmin) and root length. Post-silking DM and N accumulation were also greater with IAP than with FP under HSF conditions, accounting for 60% and 43%, respectively, of total biomass and N accumulation;however, no significant differences were found for post-silking DM and N accumulation between IAP and FP under LSF conditions. Thus, the increase in grain yield with IAP was greater under HSF than under LSF. Because of greater grain yield and N uptake, IAP significantly increased N partial factor productivity, agronomic N efficiency, N recovery efficiency, and physiological efficiency of applied N compared to FP, particularly in the HSF fields. These results indicate that considerable further increases in yield and NUE can be obtained by increasing effective soil N content and maize root length to promote post-silking N and DM accumulation in maize planted at high plant density, especially in fields with low soil fertility.

Increased grain yield with improved photosynthetic characters in modern maize parental lines

The grain yield of maize has increased continuously in past decades, largely through hybrid innovation, cultivation tech-nology, and in particular, recent genetic improvements in photosynthesis. Elite inbred lines are crucial for innovating new germplasm. Here, we analyzed variations in grain yield and a series of eco-physiological photosynthetic traits after anthesis in sixteen parental lines of maize (Zea mays L.) released during three different eras (1960s, 1980s, 2000s). We found that grain yield and biomass signiifcantly increased in the 2000s than those in the 1980s and 1960s. Leaf area, chlorophyl , and soluble protein content slowly decreased, and maintained a higher net photosynthesis rate (Pn) and improved stomatal conductance (Gs) after anthesis in the 2000s. In addition, the parental lines in the 2000s obtained higher actual photo-chemistry efifciency (ФPSI ) and the maximum PSII photochemistry efifciency (Fv/Fm), which largely improved light partition-ing and chlorophyl lfuorescence characteristic, including higher photochemical and photosystem II (PSII) reaction center activity, lower thermal energy dissipation in antenna proteins. Meanwhile, more lamel ae per granum within chloroplasts were observed in the parental lines of the 2000s, with a clear and complete chloroplast membrane, which wil greatly help to improve photosynthetic capacity and energy efifciency of ear leaf in maize parental lines. It is concluded that grain yield increase in modern maize parental lines is mainly attributed to the improved chloroplast structure and more light energy catched for the photochemical reaction, thus having a better stay-green characteristic and stronger photosynthetic capac-ity after anthesis. Our direct physiological evaluation of these inbred lines provides important information for the further development of promising maize cultivars.

An Essential Oil Blend Decreases Methane Emissions and Increases Milk Yield in Dairy Cows

This study was conducted to investigate the effect of a commercial essential oil (EO) additive on milk production and methane (CH4) emissions from dairy cows. Early lactation Holstein-Friesian dairy cows were fed grass, whole crop wheat and corn silage total mixed ration. Cows were allocated to one of two experimental treatments: Control (no additive, CON) or 1 g/head/day of EO. Cows were housed in a free stall barn, split into two pens for the duration of the experiment. Two gas data loggers units used to measure CH4 emissions were provided per pen for the duration of the 22 week-long study. Milk yield was determined daily, and milk components were analyzed every two weeks. CH4 was recorded continuously, and daily values were tabulated. Body weight and body condition score were determined at the start and bi-weekly. Results were analyzed as a randomized complete block trial. In total, 149 cows participated in the study (76 CON, 73 EO). Milk yields were greater (P < 0.05) for the test treatment (28.3 CON, 31.2 EO) with no change in milk component concentrations. Milk component concentrations were unaffected (P > 0.05) by treatment. Yields of fat, protein, lactose, and solids were higher for EO fed cows (P 4 output was reduced with the EO compared to the CON treatment (411 g/day vs 438 g/day;13.8 g/L of milk vs 17.2 g/L of milk, P < 0.05) over the duration of the trial. There were no effects of treatment on reproductive performance or the occurrence of mastitis. Feeding EO to dairy cows reduced CH4 emissions whilst also increasing performance.

Effects of straw addition on increased greenhouse vegetable yield and reduced antibiotic residue in fluvo-aquic soil

Organic manure application is an important measure for high yield and good quality vegetable production, whereas organic manure is also a main source of residual antibiotic in soils. A 3-yr experiment was conducted on a fluvo-aguic soil in Tianjin of northern China. The objective of this study was to investigate the effects of different fertilization patterns on yield of six-sea- son vegetables with celery and tomato rotation, and dynamic change of tetracyclines residues in the soil during the sixth growing season （tomato season）. The field experiment comprised six treatments depending on the proportion of nitrogen of each type of fertilizer： 4/4 CN （CN, nitrogen in chemical fertilizer）, 3/4 CN＋1/4 MN （MN, nitrogen in pig manure）, 2/4 CN＋2/4 MN, 1/4 CN＋3/4 MN, 2/4 CN＋1/4 MN＋I/4 SN （SN, nitrogen in corn straw）, and CF （conventional fertilization, the amounts of nitrogen application were 943 and 912 kg N ha-1 for celery and tomato season, respectively）. In addition to CF treatment, the amount of nitrogen application in other treatments was greatly reduced and equal （450 and 450 kg N ha-1 for celery and tomato season, respectively）. Results showed that the combined application of 3/4 CN＋1/4 MN achieved the highest yield and economic benefit in the first four seasons, but addition of straw （2/4 CN＋1/4 MN＋I/4 SN treatment） performed better in the subsequent two seasons, and the average yields of 2/4 CN＋1/4 MN＋I/4 SN treatment were respectively higher by 9.9 and 12.8% than those of 4/4 CN treatment, and by 5.6 and 10.5% than those of CF treatment. The residual chlortet- racycline （CTC） in manure-amended soil for three consecutive years increased along with the increase of applied amount of pig manure. Under the same amount of pig manure application, content of CTC in straw-amended soil was obviously decreased compared with no straw-amended soil （3/4 CN＋1/4 MN treatment）, and averagely decreased by 41.9% for four sampling periods in the sixth season. Addition of crop straw facilitated the degradation of CTC in manure-amended soil. As a whole, the conventional fertilization was not the desirable pattern based on yield, economic benefit and environment, the optimal fertilization pattern with the highest yield and profit and the least soil chlortetracycline residue was the treatment of 2/4 CN＋1/4 MN＋I/4 SN under this experimental condition.