Growth Stages Of Maize Research Articles

Combined effect of rock phosphate with single super phosphate on yield and phosphorus use efficiency under maize-groundnut cropping sequence in Alfisols of Odisha

Aim: The present study was conducted to investigate the effect of combined application of rock phosphate with water soluble phosphorus fertilizers on its efficiency in relation to soil and crop production. Methodology: Rock phosphate and single super phosphate were used as supplemental source of phosphorus and applied in variable combinations at graded doses, with maize and groundnut as test crop. Lime was applied in combination with 100% SSP to analyse its effect. The composite surface (0-15 cm) soil samples were collected at critical growth stages of maize and groundnut and further analyzed for different physical and physico-chemical characteristics. The plant samples were collected from each treatment at harvest stage for nutrient analyses. Results: Application of rock Phosphate increased the available phosphorus in soil. The combined treatment significantly influenced the yield attributes and nutrient uptake of both maize and groundnut crops. Among the combination, equal proportion of soluble single super phosphate and insoluble rock phosphate source of P outreached the other combination ratios. The highest agronomic phosphorus use efficiency and relative agronomic efficiency of the cropping sequence was obtained with the combined treatment of Single super phosphate along with lime. Interpretation: Combination of rock phosphate which has been reported to be farmer’s pocket friendly along with single super phosphate under acid soil conditions holds the potential to produce better results as compared to use of lone conventional water soluble phosphatic fertilizer like single super phosphate.

Diurnal and seasonal CO2 exchange and yield of maize cropland under different irrigation treatments in semiarid Inner Mongolia

Different irrigation treatments in plants significantly influence CO2 emissions. This study investigated the net ecosystem CO2 exchange (NEE) and yield of maize cropland under different irrigation treatments to determine the optimal irrigation treatment at different maize growth stages. Different degrees of water deficit irrigation were carried out in four fields: full irrigation, 100% evapotranspiration (ET); moderate deficit irrigation, 65% ET; and severe deficit irrigation, 40% ET. Automated static and dynamic chambers were used to measure CO2 fluxes. We found that NEE showed a “V” -shaped trend during the day and slowly declined at night. The light response parameters were calculated using the rectangular hyperbola model, and the leaf area index accounted for 85% of the light use efficiency. In the late vegetative stage, severe deficit irrigation led to a reduction in CO2 emissions but significantly reduced the crop growth rate (p < 0.05). In the reproductive stage, full irrigation not only reduced CO2 emissions but also significantly increased the crop growth rate. In the maturation stage, moderate deficit irrigation reduced CO2 emissions, and the crop growth rate decreased compared with full irrigation, but the decrease was not significant (p > 0.05). Compared with full irrigation throughout the growth period, full irrigation in the reproductive stage and moderate deficit irrigation in the late vegetative and reproductive stages both increased the maize carbon sink capacity and light use efficiency at higher leaf area index, and the harvest index did not decrease significantly. However, inadequate irrigation in the reproductive stage or severe deficit irrigation in the late vegetative and maturation stages significantly reduced the maize harvest index. Thus, full irrigation during the reproductive stage, and moderate deficit irrigation during the late vegetative and reproductive stages were the optimal irrigation strategies for saving water, reducing CO2 emissions and ensuring a satisfactory maize yield.

Unoccupied aerial systems discovered overlooked loci capturing the variation of entire growing period in maize.

Traditional phenotyping methods, coupled with genetic mapping in segregating populations, have identified loci governing complex traits in many crops. Unoccupied aerial systems (UAS)-based phenotyping has helped to reveal a more novel and dynamic relationship between time-specific associated loci with complex traits previously unable to be evaluated. Over 1,500 maize (Zea mays L.) hybrid row plots containing 280 different replicated maize hybrids from the Genomes to Fields (G2F) project were evaluated agronomically and using UAS in 2017. Weekly UAS flights captured variation in plant heights during the growing season under three different management conditions each year: optimal planting with irrigation (G2FI), optimal dryland planting without irrigation (G2FD), and a stressed late planting (G2LA). Plant height of different flights were ranked based on importance for yield using a random forest (RF) algorithm. Plant heights captured by early flights in G2FI trials had higher importance (based on Gini scores) for predicting maize grain yield (GY) but also higher accuracies in genomic predictions which fluctuated for G2FD (-0.06∼0.73), G2FI (0.33∼0.76), and G2LA (0.26∼0.78) trials. A genome-wide association analysis discovered 52 significant single nucleotide polymorphisms (SNPs), seven were found consistently in more than one flights or trial; 45 were flight or trial specific. Total cumulative marker effects for each chromosome's contributions to plant height also changed depending on flight. Using UAS phenotyping, this study showed that many candidate genes putatively play a role in the regulation of plant architecture even in relatively early stages of maize growth and development.

Direct and Residual Effect of Integrated Nitrogen Management on Physico-Chemical Properties of Soil

Aim: To find out the direct and residual effect of integrated nitrogen management on physico-chemical properties of soil under rice – maize cropping system.&#x0D; Study Design: The experiment was laid out in randomized block design during kharif season and in split plot design during rabi crop.&#x0D; Place and Duration of Study: At Agricultural college farm, Bapatla during 2018-19 and 2019-20 in Kharif and rabi seasons.&#x0D; Methodology: After the preliminary layout, paddy was sown in kharif and maize was sown in rabi season. Vermicompost and green leaf manure were applied two weeks before sowing of paddy. Treatments applied for paddy were considered as main plots and each one divided into two sub plots during rabi.&#x0D; Results: Applications of different treatments did not show any significant difference in physico-chemical properties of soil (pH and EC) at all the growth stages of rice and maize during both the years of study. Application of 75% RDN through green leaf manure + 25% RDN through inorganics (T5) to rice during kharif significantly improved organic carbon in both kharif and rabi seasons whereas different levels of fertilizers applied have not shown an significant influence on soil organic carbon content.&#x0D; Conclusion: Application of inorganic fertilizers, organic manures and their combination didn’t show marked difference on physico-chemical properties of soil like pH and EC. However substitution of 75% N through GLM in kharif season significantly improved OC content in soil during both kharif and rabi and organic carbon content was not influenced by the level of fertilizers from 50% RDF (S1) to100% RDF (S2).

Dynamics of Maize Vegetative Growth and Drought Adaptability Using Image-Based Phenotyping Under Controlled Conditions.

Changes in climate are likely to have a negative impact on water availability and soil fertility in many maize-growing agricultural areas. The development of high-throughput phenotyping platforms provides a new prospect for dissecting the dynamic complex plant traits such as abiotic stress tolerance into simple components. The growth phenotypes of 20 maize (Zea mays L.) inbred lines were monitored in a non-invasive way under control, nitrogen, and water limitation as well as under combined nitrogen and water stress using an automated phenotyping system in greenhouse conditions. Thirteen biomass-related and morphophysiological traits were extracted from RGB images acquired at 33 time points covering developmental stages from leaf count 5 at the first imaging date to leaf count 10–13 at the final harvest. For these traits, genetic differences were identified and dynamic developmental trends during different maize growth stages were analyzed. The difference between control and water stress was detectable 3–10 days after the beginning of stress depending on the genotype, while the effect of limited nitrogen supply only induced subtle phenotypic effects. Phenotypic traits showed different response dynamics as well as multiple and changing interaction patterns with stress progression. The estimated biovolume, leaf area index, and color ratios were found to be stress-responsive at different stages of drought stress progression and thereby represent valuable reference indicators in the selection of drought-adaptive genotypes. Furthermore, genotypes could be grouped according to two typical growth dynamic patterns in water stress treatments by c-means clustering analysis. Inbred lines with high drought adaptability across time and development were identified and could serve as a basis for designing novel genotypes with desired, stage-specific growth phenotypes under water stress through pyramiding. Drought recovery potential may play an equal role as drought tolerance in plant drought adaptation.

Dead level contour technical design parameters required for sustainable crop production in semi-arid areas of Zimbabwe

Smallholder farmers in sub-Saharan Africa are increasingly exposed to risks such as erratic rainfall, prolonged dry spells, and frequent droughts that threaten sustainable crop production. This study assessed the effectiveness of dead level contours with innovations (DLC INN), dead level contours with infiltration pits (DLC INFIL), dead level contours with open channels (DLC OPEN) and standard graded contours (SGCs) in harvesting and storing water in the channel, and improving crop conditions during the critical stages of maize growth on different soil textural groups in the Zvishavane District of Zimbabwe. The DLC INFIL, DLC OPEN and DLC INN outperformed the SGC under medium- and heavy-textured soils, with yields ranging between 1.7 and 2.36 t/ha compared to 0.9 t/ha for the SGC. For light textured soils, the DLC INN had the highest maize yield, averaging 0.8 t/ha. On heavy textured soils using DLC INN, DLC INFIL and DLC OPEN, smallholder farmers may use a spacing interval of 24–27 m. On medium textured soils, DLC INN and DLC INFIL can be used at a spacing interval of 18–21 m and 12 to 15 m with DLC OPEN. On light textured soils, farmers are advised to invest in DLC INN only, using a spacing interval of 12–15 m.

Potassium availability in soil amended with organic matter and phosphorous fertiliser under water stress during maize (Zea mays L) growth

Potassium can enhance plant to tolerate drought. The availability of potassium in the soil can increase with various amendments. Application organic manure to the soils increased potassium release and decrease potassium fixation in soils. Application of phosphorous fertilizer increased root biomass, photosynthesis rate and leaf water content under water stress. In this study, organic fertilizer and various sources of phosphorus were applied to the soil under the different quantity of water irrigation to evaluate potassium availability during different stages of Maize growth. The result showed that the addition of organic fertilizer increased the availability of potassium in soil at all plant stage growth. The higher quantity of water irrigation had a significantly higher concentration of potassium availability during the growth and flowering stage of Maize. However, different water quantity had no significantly effected potassium availability during the mature stage. The application of organic fertilizer and/or phosphorus fertilizer had significantly increased potassium availability as compared to the control treatment during all stage Maize growth. The interactions between treatments had significantly increased concentration of potassium availability during all stages of Maize. Therefore, organic matter and phosphorous can increased plant tolerate to drought.

An attempt to find a suitable place for soil moisture sensor in a drip irrigation system

Determination of an appropriate location for monitoring soil water content (SWC) is a key factor in efficient use of water in precision agriculture, however, the main challenge is the dynamic movement of water and root development in the soil profile. The objective of this study was investigating how SWC distribution in a loam soil profile at two growth stages of maize may impact the suitable location for SWC monitoring in a drip-tape irrigation system. A new concept, Average Moisture Representative Surface (AMRS) was proposed to determine the surface of the soil profile, which represent the average soil moisture of the wetted volume. SWC samples were taken during two irrigation intervals (48~52 days after planting (DAP) and 68~73 DAP) and root growth pattern was studied through root length density (RLD) at 50 and 100 DAP. The results revealed that a non-uniform wetting pattern after irrigation limits the appropriate locations for SWC monitoring to point measurements and with time, SWC depletion resulted in enlarging AMRS. At the end of growing season, an increase of root growth around the drippers increased the variation of root water uptake in different soil layers, and thus optimal place for soil sensors was limited to the upper layers, where the maximum root water uptake occurred. Overall, it is recommended to install soil sensors, such as tensiometers and TDRs at a horizontal distance of 5~20 cm from the crop and a depth of 10~20 cm from the soil surface while drip-tape is aligned close to the maize row.

Straw incorporation helps inhibit nitrogen leaching in maize season to increase yield and efficiency in the Loess Plateau of China

Straw incorporation and nitrogen (N) fertilization are the two important strategies to increase soil fertility and crops productivity, however their improper utilization reduces yield results in environmental pollution and wasting resources. The objective of the experiment was to evaluate the effects of straw incorporation and N fertilization and their interaction on the grain yield, nitrogen resource utilization, nitrate nitrogen (NO3−-N) dynamic changes and leaching from 2017 to 2019 in a wheat/maize rotation system in the Loess Plateau region. The experiment consists of two factors; one factor was N rates; 0 (F0), 150 (F150), 225 (F225), 300 (F300) kg ha-1, and the other factor was straw management; no straw incorporation (–S) and straw incorporation (+S). As a whole there were eight treatments in the experiment. Our results suggested that straw incorporation increased grain and nitrogen uptake, and 150 and 225 kg ha-1 increased grain and nitrogen uptake by 43.6 % and 61.8 % compared with no N fertilization. Increasing N rates gradually decreased the nitrogen recovery efficiency (NRE) and nitrogen agricultural efficiency (NAE). The unutilized N was mainly retained in the soil in the form of nitrate N, and some of the N infiltrates to 100−200 cm soil layer, showing a high N application and high leaching phenomenon, and straw incorporation effectively prevented nitrate N infiltration, and increased the nitrate N content of 0−100 cm in the middle and late stages of maize growth. Based on normalization and fitting results of yield and nitrate N accumulation in 100−200 cm soil layer, we also comprehensively evaluated the effects of N application and straw management on grain yield and environmental benefits.

SPAD Leaf Greenness Index: Green Mass Yield Indicator of Maize (Zea mays L.), Genetic and Agriculture Practice Relationship.

The study presents the results of two field studies (Experiment I, Experiment II), whose aim was to assess the impact of agriculture factors on maize green mass and leaf greenness index (Soil and Plant Analysis Development, SPAD) in critical growth stages, as well as to determine the relationship between the SPAD index and the yield of green maize for ensiling. It was shown that thermal and humidity conditions in maize growing seasons determined the value of the SPAD leaf greenness index and the yield of maize harvested for silage. Row application of mineral fertilizer (N, NP) and selection of “stay-green” varieties guarantee a higher yield of maize green mass. Growing maize in direct sowing reduces chlorophyll content expressed in SPAD units, thereby reducing plant nitrogen condition, which significantly decreases the yield of biomass intended for silage. The SPAD leaf greenness index determined in critical stages of maize growth can be considered as a yield predictor of green mass for ensiling. The examined maize cultivars were divided into two groups on the basis of hierarchically grouping using the unweighted pair group method of arithmetic means. The first group comprised cultivars SY Cooky and Drim “stay-green,” while the second one included cultivars ES Paroli “stay-green” and ES Palazzo.

Improved Aflatoxins and Fumonisins Forecasting Models for Maize (PREMA and PREFUM), Using Combined Mechanistic and Bayesian Network Modeling-Serbia as a Case Study.

Contamination of maize with aflatoxins and fumonisins is one of the major food safety concerns worldwide. Knowing the contamination in advance can help to reduce food safety risks and related health issues and economic losses. The current study aimed to develop forecasting models for the contamination of maize grown in Serbia with aflatoxins and fumonisins. An integrated modeling approach was used, linking mechanistic modeling with artificial intelligence, in particular Bayesian network (BN) modeling. Two of such combined models, i.e., the prediction model for aflatoxins (PREMA) and for fumonisins (PREFUM) in maize, were developed. Data used for developing PREMA were from 867 maize samples, collected in Serbia during the period from 2012 to 2018, of which 190 were also used for developing PREFUM. Both datasets were split randomly in a model training set and a model validation set. With corresponding geographical and meteorological data, the so-called risk indices for total aflatoxins and total fumonisins were calculated using existing mechanistic models. Subsequently, these risk indices were used as input variables for developing the BN models, together with the longitudes and latitudes of the sites at which the samples were collected and related weather data. PREMA and PREFUM were internally and externally validated, resulting in a prediction accuracy of PREMA of, respectively, 83 and 70%, and of PREFUM of 76% and 80%. The capability of PREMA and PREFUM for predicting aflatoxins and fumonisins contamination using data from the early maize growth stages only was explored as well, and promising results were obtained. The integrated approach combining two different modeling techniques, as developed in the current study, was able to overcome the obstacles of unbalanced data and deficiency of the datasets, which are often seen in historical observational data from the food safety domain. The models provide predictions for mycotoxin contamination at the field level; this information can assist stakeholders of the maize supply chain, including farmers, buyers/collectors, and food safety authorities, to take timely decisions for improved mycotoxin control. The developed models can be further validated by applying them into practice, and they can be extended to other European maize growing areas.

Factors Affecting the Establishment and Growth of Cover Crops Intersown into Maize (Zea mays L.)

In the North Central USA, intersowing cover crops into standing maize (Zea mays L.) is required to establish plants large enough to afford the benefits of a cover since there is limited favorable weather for cover crop growth after maize harvest. The objective of this study was to quantify the impacts of the planting method and time of planting of three cover crop species when grown with or without maize competition on their establishment. Experiments were conducted in three environments during 2018 and 2019. Experiments consisted of a factorial combination of timing of cover crop planting (V7 and R4 growth stage of maize), cover crop species (camelina (Camelina sativa (L.) Crantz), rye (Secale cereale L.), or radish (Raphanus sativus L.), method of sowing (drilled or broadcast), and maize removal. Initial cover crop populations were similar regardless of maize removal or stage of maize when sown, but intersown cover crops produced only 3% of the fall biomass, compared with treatments with maize-removed when sown at the V7 stage of maize and 14% when sown at the R4 stage. Limited light intensity (less than 20%) under the maize canopy was the main factor affecting interseeded cover crop development. Radish was more sensitive to shading than the other cover crops. Camelina and rye sown at the R4 stage of corn produced similar spring biomass as earlier-sown cover crops. Intersown cover crops had no negative effect on maize grain yield.

Effect of weather parameters on growth stages of winter maize explain the grain yield

A study was conducted on research farm of National Maize Research Program (NMRP), Rampur, Chitwan, Nepal during winter season of 2015/16 laid out in split-split plot design with three replications consisting of two FYM levels (FYM at 10 t ha-1 and no FYM application), three nitrogen levels (100, 75 and 50% N of recommended dose P and K remaining constant) and two levels of seed inoculation (Azotobacter chrococcum seed inoculation and no inoculation) with Rampur-2 maize hybrid in Nepal. One of the major factor affecting maize production is weather and this paper is prepared to assess the suitability of weather condition at different growth stages of winter season hybrid maize in condition of western Chitwan, Nepal at NMRP. The result shows that the requirement of the maize crop during different growth stages i.e. temperature, rainfall, relative humidity were fulfilled which helped to obtain remarkably higher grain yield (4.26 t ha-1) in the experiment compared to average national grain yield (2.84 t ha-1) of maize

Slow-release nitrogen fertiliser suitable for one-time fertilisation of spring maize in Northeast China

Slow-release nitrogen fertiliser can potentially increase crop production and improve fertiliser nitrogen use efficiency. However, it is unclear that are suitable for different regions and crops in the northeast of China. Therefore, according to different soil and climate characteristics, we investigated the synchronised relationships between nitrogen slow release fertiliser and nitrogen maize requirements. Experiments were conducted at Shenyang Agricultural University, Liaoning province, Northeast China, from 2016 to 2017. Stabilised fertiliser treatments increased grain yield, nitrogen use efficiency and nitrogen accumulation at each maize growth stage. Grain yield increased by 2.32% and 11.33% (2016), and 1.55% and 7.87% (2017), respectively, when compared with the urea CK1 (233 kg N/ha) and CK2 (210 kg N/ha) treatments. Additionally, during the growth period of the stabilised fertiliser treatment, the stability of the synchronisation relationship between nitrogen absorption and absorption of spring maize was significantly higher than other treatments, and the effect was the best. Therefore, we conclude that the stabilised fertiliser is the most suitable option for promotion and application in spring maize in Northeast China.

Varietal response of maize to nitrogen and zinc fertilizer in Minna Southern Guinea Savanna of Nigeria

A field experiment was conducted in 2018 and 2019 seasons at the Teaching and Research Farm of the Federal University of Technology, Minna to determine the varietal response of maize to nitrogen and zinc fertilizer in Minna. The treatments included four levels of N: 0, 30, 60 and 90 kg ha-1, three levels of Zn: 0, 2.5 and 5 kg ha-1 and two varieties of maize (Oba Super 2 and Suwan-1-SR). The experimental design was a 4×3×2 factorial design fitted in a randomized complete block design with three replications. The data collected were, plant height, number of leaves, cob weight, cob length, stover yield, grain yield and 1000 grain weight. All data collected were subjected to analysis of variance and the means were separated using Duncan Multiple Range Test. Highest plant height (43.69 and 44.37 cm) were obtained in 60 and 90 kg N ha-1 treatment application respectively in year 2018 at 3 Week After Sowing (WAS), these heights were significantly different from that of control (0 kg N ha-1). Zinc (Zn) fertilization has no significant effect on maize height at all growth stage of maize in year 2018. Application of Zn produced significantly taller plants than those without Zn application at 3 and 9 WAS in 2019. The treatment 60 kg N ha-1 had significantly higher yield (27873.7 kg ha-1) than others but similar to 90 kg N ha-1 (2512.4 kg ha-1). Application of 60 kg N ha-1 increased with 12 % than the 0 kg N ha-1 on maize yield in 2019. There was response to Zn fertilization on stover and grain yields. The interaction effects were significant on stover yield. The nitrogen rate of 60 kg N ha-1 and the zinc rate of 2.5 kg were optimum for maize grain yield in Minna, both Oba Super 2 and Suwan-1-SR performed better in the study.

Co-designing Indices for Tailored Seasonal Climate Forecasts in Malawi

In central and southern Malawi, climate variability significantly impacts agricultural production and food availability owing to a high dependence on rain-fed maize production. Seasonal climate forecast information has the potential to inform farmers' agricultural planning, thereby improving preparedness to extreme events. In this paper we describe and evaluate an approach to co-designing and testing agro-climatic indices for use in seasonal forecasts that are tailored to farmer-defined decision-making needs in three districts of central and southern Malawi. Specifically, we aim to (a) identify critical maize specific agro-climatic indices by engaging key stakeholders and farmers; (b) compare and triangulate these indices with the historical climate record in study districts; and (c) analyze empirical relationships between seasonal total rainfall and maize specific indices in order to assess the potential for forecasting them at appropriate seasonal timescales. The identified agro-climatic indices include critical temperature/rainfall thresholds that are directly associated with phenological stages of maize growth with direct implications for maize yield and quality. While there are statistically significant relationships between observed wet season rainfall totals and several agro-climatic indices (e.g., heavy rainfall days and dry spell), the forecast skill of the UK Met Office's coupled initialized global seasonal forecasting system (GloSea5) over Malawi is currently low to provide confident predictions of total wet season rainfall and the agro-climatic indices correlated with it. We reflect on some of the opportunities and challenges associated with integrating farmers' information needs into a seasonal forecast process, through the use of agro-climatic indices.

Low soil phosphorus availability triggers maize growth stage specific rhizosphere processes leading to mineralization of organic P

In this study, we examine the rhizosphere processes influencing organic P (Po) utilization in soil with low inorganic P (Pi) availability and how they change with plant development. Interactions between plants and the rhizosphere microbial community triggered by P deficiency may provide insights into the role of P availability on degradation of soil organic matter (SOM). Maize (Zea mays) plants were grown in low P containing soil. Soil pH, potential acid phosphatase activities, soil C and P pools, microbial biomass C and P, microbial community structure, and plant P content were analyzed at different vegetative growth stages (VGS). At early VGS, the plants were P deficient which correlated with greater rhizosphere potential acid phosphatase activity, degradation of SOM and a reduction in the Po pool. At late VGS, the plants appeared to recover which correlated with a decrease in Meh (III) extractable P, an increase in microbial biomass C and P, change in microbial community structure, and greater total P (TP) in the plant biomass. The mineralization of organic C and Po are coupled in low P soil where N is not limited. The overall findings from this study advance our understanding of the coupled biogeochemical rhizosphere processes controlling P cycling at different plant growth stages and notably the importance of Po to the overall P needs of plants in soil with low Pi availability.

Evaluation of furrow fertigation on nitrogen supply and losses as a function of maize growth stages

The purpose of this study was to evaluate the effects of furrow fertigation on nitrate deep leaching, nitrate runoff losses, and plant nitrogen supply in various growth stages of maize (Zea mays L.). Furrow fertigation experiment was conducted in 120 (W1), 100 (W2), 80 (W3), and 60% (W4) levels of required water (560 mm) and 100 (N1), 80 (N2), 60 (N3), and 0% (N4) levels of required nitrogen fertilizer (184 kg N ha−1). N-fertilizer was applied in four split applications (before planting, at the seven-leaf, shooting, and flowering). In the farmers’ conventional fertilization (FCF) method, 120% level of required water and 100% level of the required N-fertilizer were used in two split applications (before planting and at the seven-leaf stage). Results showed that the highest maize aboveground nitrogen content was 3.11% for FCF treatments at the seven-leaf stage. The maximum nitrogen content in the sensitive flowering stage and the maximum grain yield were also observed in W2N1 treatment with 2.27% and 12.93 ton ha−1, respectively. While, there were no significant differences in aboveground nitrogen content and grain yield between W2N1 and W3N1, W2N2, and W3N2. The highest amounts of nitrate leaching out of the 80-cm soil layer and nitrate runoff losses, were also recorded in FCF treatment, followed by W1N1, W2N1, and W3N1. Based on plant nitrogen content, nitrate losses and maize yield, 80% levels of the required N-fertilizer and required irrigation water could be recommended as the optimal levels to reduce nitrate losses and improve maize yield.

基于SPEI的辽宁省玉米生育期干旱特征分析

在全球气候变暖的背景下，探究玉米生育期的气候变化及干旱特征，对于预防干旱灾害对作物造成的损失，以及农业可持续发展意义重大。基于1967—2018年辽宁省33个国家级气象台站逐日观测数据，计算了不同月尺度下玉米各生育期标准降水蒸散指数（SPEI），并结合干旱频率及干旱站次比综合分析了干旱时空变化情况。结果表明：（1）辽宁省玉米生育期降水量以13.31 mm/10a的速率减少，与SPEI呈显著正相关（P<0.01）；气温以0.25℃/10a的速率显著上升（P<0.01），与SPEI呈负相关。（2）播种-出苗期、出苗-拔节期和喇叭口期SPEI在时间上均呈上升趋势，抽雄期和成熟期呈降低趋势；在空间上全生育期SPEI表现为西北向东南递增趋势。（3）全生育期干旱站次比以0.41%/10a的速率上升；出苗-拔节期干旱站次比呈减少趋势，其他生育阶段均呈上升趋势；发生干旱类型频次区域性干旱 > 部分区域性干旱 > 局域性干旱 > 全域性干旱。（4）全生育期干旱频率整体呈现出由西北向东南递减的特征，且干旱频发区主要在辽西地区；干旱发生频率轻旱 > 中旱 > 重旱 > 特旱。（5）出苗-拔节期为干旱站次比最高的时期；SPEI平均值和不同等级干旱频率最高的时期均为播种-出苗期。该研究成果可为区域农业干旱风险评价以及抗灾减灾等提供参考。;In the context of global warming, it is of great significance to explore the climate change and drought characteristics of maize growth period for preventing crop loss caused by drought disaster and agricultural sustainable development. Based on the daily observation data of 33 national meteorological stations in Liaoning Province from 1967 to 2018, this study calculated the standard precipitation evapotranspiration index (SPEI) at different growth stages of maize on monthly scales, and comprehensively analyzed the temporal and spatial variation of drought with the combination of drought frequency and drought station ratio. The results showed that:(1) the precipitation in the growth period of maize in Liaoning Province decreased by 13.31 mm/10a, which was significantly positively correlated with SPEI (P<0.01); temperature increased significantly at a rate of 0.25℃/10a (P<0.01), which was negatively correlated with SPEI. (2) In sowing-seedling stage, emergence-jointing stage and bell-mouth stage, SPEI all showed an upward trend, while in tasseling stage and maturation stage showed a downward trend. In terms of spatial variation, SPEI showed an increasing trend from northwest to southeast in the whole growth period. (3) During the whole growth period, the drought station ratio increased at a rate of 0.41%/10a. In the emergence-jointing stage, the ratio of drought stations decreased, while in other growth stages, it increased. The frequency of different drought types manifested as regional drought > partial regional drought > local drought > all regional drought. (4) The drought frequency of the whole growth period showed a characteristic of decreasing from northwest to southeast, and the drought-prone area was mainly in western Liaoning; and the drought frequency showed in order of light drought > medium drought > heavy drought > severe drought. (5) The emergence-jointing stage was the period with the highest drought station ratio; the highest average SPEI and the drought frequency of different grades were both in the sowing-seedling stage. The research results can provide reference for regional agricultural drought risk assessment and disaster mitigation.

大气CO2浓度升高对春玉米土壤呼吸的影响

为探讨春玉米不同生育期土壤呼吸速率对大气CO₂浓度升高的响应，以黄土高原旱作春玉米为研究对象，通过改进的开顶式气室（OTC）模拟大气CO₂浓度升高的环境，在田间条件下设置自然大气CO₂浓度（CK）、OTC对照（OTC，CO₂浓度同CK）与CO₂浓度升高（OTC+CO₂，OTC系统自动控制CO₂浓度700 μmol/mol）3种处理。研究了旱区覆膜高产栽培春玉米播前（V0）、六叶期（V6）、九叶期（V9）、吐丝期（R1）、乳熟期（R3）、蜡熟期（R5）及完熟期（R6）土壤呼吸速率对大气CO₂浓度升高的响应特征，以及大气CO₂浓度升高对土壤呼吸速率的温度与水分效应的影响。研究发现，OTC+CO₂处理土壤呼吸速率，与CK相比，在R3和R5期分别增加43%、104%（P<0.05），与OTC相比，R3和R5期分别提升了63%、109%（P<0.05）；OTC处理与CK相比，在整个生育期对土壤呼吸影响不显著；3种处理条件下，土壤温度和水分随生育期变化趋势基本一致，土壤呼吸速率与土壤温度和水分分别呈指数相关和抛物线型相关；结果表明：大气CO₂浓度升高对土壤呼吸的影响因生育期而异，土壤温度和土壤水分是影响旱地农田土壤呼吸的重要因素，CO₂浓度升高会使土壤呼吸温度效应值（Q₁₀）降低，土壤呼吸对土壤水分响应的阈值提高。;Understanding the effects of elevated atmospheric CO₂ on soil respiration is crucial for predicting the greenhouse gas emission in the future. A field experiment was conducted to study the effects of elevated CO₂ on soil respiration of spring maize under three atmospheric conditions (treatments):natural atmospheric conditions with the current CO₂ concentration (marked as CK), open-top chamber (OTC) system with the current atmospheric CO₂ concentration (as the contrast, marked as OTC), and OTC system with elevated CO₂ concentration of 700 μmol/mol (marked as OTC+CO₂). Soil respiration, soil temperature and moisture were measured at the main growth stages of spring maize including pre-sowing (V0), jointing stage (V6), ninth-leaf stage (V9), silking stage (R1), milk stage (R3), dent stage (R5), and physiological maturity stage (R6). The results showed that, compared with CK, OTC+CO₂ enhanced soil respiration rates by 43% and 104% (P<0.05), respectively, at the R3 and R5 stage. Compared with OTC, OTC+CO₂ increased soil respiration rates by 63% and 109% (P<0.05) at the R3 and R5 stage, respectively. There was no significant difference in soil respiration between OTC and CK during the whole growth period of spring maize. The changing dynamics of soil temperature with growth period for the three treatments were consistent, also soil moisture changing dynamics with growth period under the three atmospheric conditions were similar. Soil respiration showed an exponential and parabolic correlation with the soil temperature and soil moisture, respectively. In conclusion, the effects of elevated CO₂ on soil respiration varied with growth stage. Soil temperature and soil moisture were the main factors affecting soil respiration, the elevated CO₂ decreased the temperature effect value (Q₁₀), and increased the threshold value of soil respiration to soil moisture.