Maize In Northeast China Research Articles

Improving Northeast China’s soybean and maize planting structure through subsidy optimization considering climate change and comparative economic benefit

The planting structure of Northeast China (NEC) is greatly responsible for China’s food security and self-sufficiency. Climate change promoted the northward expansion of the suitable planting area for maize in NEC, and its higher comparative economic benefit largely helped it occupy the soybean planting space. Yet, knowledge on how climatic suitability and comparative economic benefit affected the northward expansion of maize planting area is limited. To bridge this gap, this study quantified the climatic suitability of maize and soybean from 1981 to 2020 using the fuzzy mathematical method. Combined with yield, crop distribution and social economic data in 2000, 2010 and 2020, this study further calculated the comparative economic benefit between the two crops. Furthermore, a crop planting decision simulation model was developed to clarify the impact of climatic suitability and comparative economic benefit on the planting area of soybean and maize. Results showed that from 2000 to 2010, the maize planting area increased dramatically. This was due to the continuous northward expansion of the most suitable region (S1) for maize from 47.63°N to 48.43°N before 2010, along with the fact that 65% of the total area was more profitable to plant maize. From 2010 to 2020, the maize planting area partially retreated, mainly due to the shrinking trend of the northern boundary of S1 for maize and the implementation of soybean producer subsidy. The improvement of maize climatic suitability played a fundamental role in the northward expansion of its planting area. On this basis, the comparative economic benefit was critical for planting proportion adjustments. The current soybean producer subsidy largely reduced the profit gap between the two crops, but it was still insufficient in nearly one-third of the total area. This study suggested to increase amount of soybean subsidies in the identified soybean-maize imbalanced regions. Specifically, the average recommended increase amounts ranged from 756 to 2052 CNY/ha depending on the regions. These findings could provide valuable references for understanding the motivation of crop planting decisions and optimizing the corresponding subsidy policies.

Drought risk assessment for early maize growth in Northeast China based on a reconstructed phenological dataset

AbstractDrought is one of the meteorological disasters to which maize is most vulnerable during its seedling stage in Northeast China. The absence of phenological data impedes the precise evaluation of the likelihood of drought during this phase. In response to these issues, this study develops a phenology model and reconstructing the data. Furthermore, it effectively assessed drought risk at the site scale by utilizing drought indicators. Using reconstructed phenological data from 217 sites from 1981 to 2015, we analysed the duration and trends of each phenological period and assessed the spatial and temporal distribution of drought frequency at each growth stage. The study demonstrated that the average date ranges for the sowing, emergence, three‐leaf, and seven‐leaf stages annually were 115–138 days, 130–151 days, 135–160 days, and 150–180 days, respectively. Additionally, there was a significant trend towards earlier dates in all phenological stages. Our research reveals notable fluctuations in drought frequency during various growth stages of early maize in Northeast China. Particularly, the period from the three‐leaf to the seven‐leaf stages emerges as the most drought‐prone, while the initial emergence to three‐leaf stage also shows considerable vulnerability. On average, the frequency of drought events during the critical three‐ to seven‐leaf stage stands at 35%. This average is surpassed in regions like Heilongjiang, northwest Jilin, northern Inner Mongolia, and southwest Liaoning, indicating a heightened risk in these areas. The early maize growth stage drought types are mainly light and moderate drought, with the three‐leaf to seven‐leaf stage, and Heilongjiang and Inner Mongolia, as the key stages and regions of concern, respectively. Identifying the principal types of drought and their occurrence in distinct regions and growth stages is pivotal for averting and reducing disasters.

Effects of Temperature on Growth and Grain Maturity of Spring Maize in Northeast China: A Study of Different Sowing Dates

Situated at middle-to-high latitudes with limited thermal resources, Northeast China is the primary maize-producing region in China. It is also one of the regions most significantly impacted by climate change. Given the persistent impact of climate change, it is crucial to elucidate the effects of the varying thermal conditions and low temperatures for different sowing dates on the growth, development, and grain maturity of spring maize. To ensure secure maize production and disaster prevention, choosing the optimal sowing time for spring maize holds significant implications for the judicious utilization of climatic resources, risk mitigation, and the provision of meteorological guidance. Moreover, it can serve as a technical reference for relevant departments to conduct climate evaluation, disaster monitoring, prediction, and assessment, as well as impact analysis of corn production safety. Additionally, it can provide meteorological evidence to ensure food security and promote the sustainable development of modern agriculture. An interval sowing experiment of spring maize was conducted in Harbin in the north of Northeast China. Two varieties were used in the experiment. Four sowing dates were set, and the interval between adjacent sowing dates was 10 days. The local perennial sowing time, 5 May, was set as the second sowing date, with one date set later and two dates set earlier. During the experiment, the growth process, grain dry matter, seed moisture content, yield components, and temperature of spring maize were observed. The impact of temperature conditions on maize growth and yield formation was analyzed in this paper through mathematical statistics, which further led to the establishment of a monitoring and evaluation model for assessing the effect of thermal conditions and temperature on maize. The results showed that the growth rate of spring maize was closely related to temperature. When the average temperature, minimum temperature, and maximum temperature increased by 1 °C, the average emergence rate increased by 1.05%, 0.99%, and 1.07%, respectively, and the average vegetative growth rate increased by 0.16%, 0.16%, and 0.09%, respectively. The change rate of ≥10 °C active accumulated temperature was significantly correlated with the change rate of the dry weight of the grain kernel, which conformed to the quadratic equation of one variable. The temperature influence coefficients of different sowing dates varied from 1.0% to 1.7%. The relationship between the accumulated values of 10 ℃ active accumulated temperature and the grain moisture content of spring maize was a logarithmic function. From 10 to 50 days after anthesis, the effect of temperature can explain about 95% of the change in grain moisture content. After physiological maturity, the effect of thermal conditions can only explain 56–83%. The temperature influence coefficient ranges from 1.3% to 13.8%. Comparatively speaking, the second sowing date is the most suitable sowing date. Early sowing is prone to encounter low temperatures, resulting in underutilization of the early heat, while late sowing is prone to less heat. Both conditions are not conducive to better improve the yield of spring maize.

Comprehensive assessment of the agronomic, environmental and economic benefits effects of nitrogen fertigation management on maize in Northeast China

ABSTRACT Seeking economical, efficient and environmentally friendly nitrogen fertigation management strategies is extremely important for sustainable maize production. A two-year field experiment was conducted to investigate the effects of four nitrogen fertilization methods N0: no nitrogen application; FP: applying 234 kg N ha−1 at sowing; NF1: applying 210 kg N ha−1, 50% N at sowing and 50% N fertigation at the V8 stage; and NF4: applying 210 kg N ha−1 sowing: 30%, fertigation at V8: 20%, V12: 20%, R1: 20%, R3: 10% on maize yield, nitrogen and water use efficiency, economic benefits and the environmental assessment in Northeast China. The results showed that compared with the FP treatment, the NF1 and NF4 treatments significantly increased maize yield by 13.2% and 18.6%, increased recovery efficiency of nitrogen (REN) by 38.6% and 68.4%, agronomic nitrogen efficiency (AEN) by 58.6% and 78.2%, water use efficiency (WUE) by 23.8% and 26.9%, and net income by 16.1% and 25.7%, respectively. Additionally, the treatments reduced the apparent nitrogen loss by 69.5% and 96.1%, nitrogen footprint by 34.4% and 37.4% and carbon footprint by 17.0% and 20.8%, respectively. The yield, REN and net income of NF4 were significantly higher than those of NF1 by 4.8%, 21.6% and 8.3%, respectively, and the nitrogen and carbon footprints of NF4 were significantly lower than those of NF1 by 4.6% and 4.6%, respectively. The NF4 treatment was recommended as an effective method for improving yield and net income and reducing the environmental cost while achieving sustainable maize production.

The heat stress during anthesis and the grain-filling period of spring maize in Northeast China is projected to increase toward the mid-21st century.

Against the background of global warming, heat stress has become more frequent, which adversely affects the growth and development of spring maize plants in Northeast China. To adapt the regional maize production to climate change, it is imperative to understand the spatio-temporal characteristics of heat stress. In the present study, we analyzed three of the indices for heat stress, including the number of heat stress days, heating degree days (HDD, the total heat degree-days during critical stages), and the percentage of stations with heat stress. From 1981 to 2019, the number of heat stress days varied greatly among the study years, ranging from 0 to 14 and 27 days, respectively. The average HDD was 7.8 and 5.0 °C day from 1981 to 2000, respectively, and the main hot-spots of heat stress occurred in the southwest regions. Moreover, compared with 1981-2000, the region of HDD during anthesis higher than 10 °C day in 2041-2060 under the SSP1-2.6 and SSP5-8.5 climate scenarios increased by 9.1-50.1% and 0.1-28.6%. The average HDD during the critical stages from 2041 to 2060 increased under the SSP5-8.5 climate scenario, being 1.5 times higher than that during 1981-2000. HDD during maize anthesis and the grain-filling period showed an overall increasing trend with years. About 19% and 58% of the study locations showed heat stress during the past 39 years, respectively. Heat stress during anthesis and the grain-filling period for spring maize in Northeast China is projected to increase toward the mid-21st century. © 2023 Society of Chemical Industry.

Effects of Straw Return and Nitrogen Fertilization on Grain Yield and Leaf Senescence of Maize in Northeast China

Effects of Straw Return and Nitrogen Fertilization on Grain Yield and Leaf Senescence of Maize in Northeast China

Nitrogen Application Effect on Maize Yield, NH3, and N2O Emissions in Northeast China by Meta-Analysis

Ammonia volatilization (NH3) and nitrous oxide (N2O) emission are the main underliers of nitrogen loss in farmlands, which can decrease nitrogen use efficiency and trigger environmental problems regarding greenhouse effects. Previous studies have regional limitations and lack universal guiding significance, as they are primarily based on individual experiments related to the effects of applying nitrogen fertilizer on maize. In this study, we performed a meta-analysis on a regional scale to investigate the overall impact of nitrogen fertilizer application on maize yield, N2O, and NH3 in Northeast China. The database included 85 studies and 1147 pairs of experimental data that were analyzed. The results showed that applying nitrogen fertilizer significantly increased maize yield, N2O emissions, and NH3 volatilization effects, and the growth rates (E) were 50.64%, 64.39%, and 69.25%, respectively. In Northeast China, the average emission factors of N2O and NH3 were 0.72% and 8.21%, respectively. The optimum nitrogen application rate for maize in Northeast China was 205 kg ha−1, resulting in 8.37% nitrogen loss (through N2O and NH3). Soil texture, alkaline nitrogen (AN) content in the soil, mean annual precipitation (MAP), nitrogen application rate, and fertilizer type were the key influential factors affecting changes in maize yield and N loss (N2O and NH3). Yield-scaled N2O and NH3 were found to be the significant emission reduction parameters that ensured maize yield. However, there was a remarkable ‘seesaw effect’ between yield-scaled N2O and NH3 under the same natural conditions (MAP and soil texture). Therefore, human activities such as reducing N surplus in soil, and N fertilizer application rate, along with selecting suitable fertilizer types should be given more attention to reduce yield-scaled N2O and NH3. Moreover, minimizing NH3 and N2O dual emission should be the main objective for green agriculture in Northeast China, rather than over-emphasizing on single emission reduction.

Responses of dry matter accumulation and partitioning to drought and subsequent rewatering at different growth stages of maize in Northeast China.

Dry matter accumulation (DMA) and dry matter partitioning (DMP) are important physiological processes determining crop yield formation. Deep understanding of the DMA and DMP processes and their responses to drought are limited by difficulty in acquiring total root biomass. Pot experiments with treatments quitting and ceasing ear growth (QC) and controlling soil water (WC) during vegetative (VP) and reproductive (RP) growth stages of maize (Zea mays) were conducted in Jinzhou in 2019 and 2020 to investigate the effects of drought and rewatering on DMW and DMP of different organs. The response of DMW of reproductive organ to drought was more sensitive than those of vegetative organs, and was maintained after rehydration. Drought during VP (VPWC) reduced more sharply DMW of stalk than of leaves, and that during RP (RPWC) decreased more substantially leaves DMW. The effect of drought on DMPR was inconsistent with that on DMW for each organ. The DMP patterns of maize in different growth stages have adaptability to some level of water stress, and their responses increased with drought severity. Drought increased significantly DMP rates (DMPRs) of vegetative organs and reduced the ear DMPR and harvest index (HI), attributing to the suppressed photosynthates partitioning into ear and dry matter redistribution (DMRD) of vegetative organs, especially for stalk DMRD decreasing 26%. The persistence of drought impact was related to its occurrence stage and degree as well as the duration during rewatering to maturity. The aftereffect of drought during different growth periods on DMP were various, and that of VPWC enlarged and drastically induced the reduction of HI, also was larger than that of RPWC which demonstrated obvious alleviation in the previous responses of DMP and HI. Root-shoot ratio (RSR) increased under VPWC and RPWC and subsequent rehydration. The DMWs of stalk, roots and leaves were affected by VPWC in order from large to small, and were close to or larger than the controls after rehydration, indicating the compensation effect of rewatering after drought. The DMPRs, RSR AND HI are the important parameters in agricultural production, and are often used as the constants, but in fact they vary with plant growth. In addition, the interannual differences in ear and stalk DMPRs in response to drought were probably caused by the difference in degree and occurrence stage of drought, further reflecting the variation in response of allometry growth among organs to the environment. Besides, the persistence of drought impact was related to the occurrence stage and degree of drought, which is also associated with the duration during rewatering to maturity. Notably, the effect of drought on DMW was inconsistent with that on DMPR for each organ meaning that the two variables should be discussed separately. The QC did not affect total DMW but increased RSR, changed and intensified the effect and aftereffect of RPWC on DMP, respectively, indicating that the DMP pattern and its response to drought occur change under the condition of QC.

Effects of Carbon-Based Fertilizer on Soil Physical and Chemical Properties, Soil Enzyme Activity and Soil Microorganism of Maize in Northeast China

The soil environment is an important factor that affects the growth of maize. Our study discusses the effect of carbon-based fertilizer on the rhizosphere soil microenvironment. Xianyu 335 and Jingke 968 maize varieties were selected, and six treatments were set up as follows: no fertilizer, chemical fertilizer, or carbon-based fertilizer (3 t/hm2, 3.75 t/hm2, 4.5 t/hm2, and 5.25 t/hm2). The results showed that the carbon-based fertilizer significantly reduced the soil pH value in the late growth stage. Carbon-based fertilizer can significantly improve the conductivity of soil solution. On 8 July (jointing stage), the conductivity of the two varieties of soil was the highest at 3.75 t treatment, 259.38% and 169.26% higher than that of chemical fertilizer, respectively. Carbon-based fertilizer significantly increased the soil carbon flux. The soil carbon flux of Jingke 968 showed a trend of first rising and then falling with the increase in the application amount of carbon-based fertilizer. On 8 July (jointing stage) and 28 July (tasseling stage), the 4.5 t treatment reached the maximum value, and on 16 August (early filling stage) and 4 September (waxy stage), the 3.75 t treatment reached the maximum value. Carbon-based fertilizer significantly increased the content of nitrate nitrogen, ammonium nitrogen, available phosphorus, and available potassium in the topsoil. Carbon-based fertilizer had a significant effect on soil enzyme activity and significantly increased soil neutral phosphatase activity in the late growth stage. On 16 August (early stage of grouting), β-Glucosidase activity was significantly higher in 3 t and 3.75 t treatments than other treatments in Xianyu 335 and Jingke 968. The activity of α-Xylosidase reached the highest at 3.75 t. The activities of polyphenol oxidase and catalase reached their maximum at 5.25 t treatment on 4 September (waxy ripening) and 26 September (full ripening). Carbon-based fertilizer significantly increased the soil bacterial diversity index (Shannon index, ACE index and Chao1 index), but had no significant impact on the fungal diversity index, and significantly increased the abundance of soil bacterial and fungal populations.

Drought and Waterlogging Status and Dominant Meteorological Factors Affecting Maize (Zea mays L.) in Different Growth and Development Stages in Northeast China

Drought and floods affect the growth and yield of maize, affecting food security. Therefore, it is crucial to assess maize’s drought and waterlogging status in various growth stages. We used phenological and daily meteorological data and spatial analysis to identify the drought and waterlogging conditions of spring maize in Northeast China in eight growth stages. We calculated the crop water surplus/deficit index and used the national standard for maize drought and waterlogging. The results indicate a significant decreasing trend of effective precipitation in Northeast China. The maize’s water requirements changed during the growing period. The ranking of the daily water requirements of maize from high to low in the different growth stages was the flowering stage to the silking stage (6.9 mm/d), the tasseling stage to the flowering stage (6.1 mm/d), the jointing stage to the tasseling stage (4.9 mm/d), the seven-leaf stage to the jointing stage (3.4 mm/d), the silking stage to the harvesting stage (2.0 mm/d), the emergence stage to the three-leaf stage (1.4 mm/d), the three-leaf stage to the seven-leaf stage (1.3 mm/d), and the sowing stage to the emergence stage (1.2 mm/d). Drought occurred primarily in the early growth and development stage, and the most severe drought conditions were observed in the sowing to emergence stages and the emergence to the three-leaf stages in most areas in Northeast China. Waterlogging occurred predominantly in the flowering to the silking stages and the silking to the maturity stages in southeast Liaoning and parts of Jilin. Inner Mongolia had the lowest soil moisture conditions and was unsuitable for maize growth, followed by Heilongjiang, Jilin, and Liaoning. The dominant meteorological factors affecting the drought and waterlogging status of maize in different growth stages were precipitation and wind speed, followed by the minimum temperature, relative humidity, sunshine hours, and maximum temperature. The average temperature did not influence the drought and waterlogging status. The results provide a basis for selecting drought-resistant varieties and preventing waterlogging.

Spatio-temporal variations and drought of spring maize in Northeast China between 2002 and 2020.

A lot of spring maize is grown in Northeast China (Liaoning, Jilin, and Heilongjiang), an area that is highly susceptible to drought. Here, remote sensing indexes from 2002 to 2020 were studied using the 8-day surface reflectance and land surface temperature of Moderate-resolution Imaging Spectroradiometer data. Spring maize distribution was extracted using a decision tree classification, and the results were compared to the known distribution based on field investigation data and published statistics. The results showed that mixed pixels of spring maize and soybeans had limited influence on the study of spatio-temporal variations of spring maize, and the error was acceptable. The overall accuracy of verifying the spring maize distribution from 2018 to 2020 was above 85%. The stable, fluctuating, and low-frequency planting areas of spring maize accounted for 11.86%, 17.41%, and 34.86% of the study area, respectively. In 2015, the government directed a reduction of the planting area of spring maize in the "Liandaowan" region of Northeast China. The planting area of spring maize was characterized by a continuous increase before this change (2002-2014), exhibited changes and reductions in response to the change (2015-2017), and exhibited optimization and recovery after this change (2018-2020). Compared with the fluctuating and low-frequency planting areas, moderate and severe droughts were higher in stable planting areas. From 2002 to 2020, the most severe droughts occurred in the expanded planting areas. This rapid and large-scale monitoring of spatio-temporal variations and drought of spring maize provides a foundation for improving grain yield. This method could be easily applied to the study of other regions and combined with high-resolution and hyperspectral satellite data to improve monitoring accuracy.

Yield Response of Spring Maize under Future Climate and the Effects of Adaptation Measures in Northeast China

Agriculture production has been found to be the most sensitive sector to climate change. Northeast China (NEC) is one of the world’s major regions for spring maize production and it has been affected by climate change due to increases in temperature and decreases in sunshine hours and precipitation levels over the past few decades. In this study, the CERES-Maize model-v4.7 was adopted to assess the impact of future climatic change on the yield of spring maize in NEC and the effect of adaptation measures in two future periods, the 2030s (2021 to 2040) and the 2050s (2041 to 2060) relative to the baseline (1986 to 2005) under RCP4.5 and RCP8.5 scenarios. The results showed that increased temperatures and the decreases in both the precipitation level and sunshine hours in the NEC at six representative sites in the 2030s and 2050s periods based on RCP4.5 and RCP8.5 climate scenarios would shorten the maize growth durations by (1–38 days) and this would result in a reduction in maize yield by (2.5–26.4%). Adaptation measures, including altered planting date, supplemental irrigation and use of cultivars with longer growth periods could offset some negative impacts of yield decrease in maize. For high-temperature-sensitive cultivars, the adoption of early planting, cultivar change and adding irrigation practices could lead to an increase in maize yield by 23.7–43.6% and these measures were shown to be effective adaptation options towards reducing yield loss from climate change. The simulation results exhibited the effective contribution of appropriate adaptation measures in eliminating the negative impact of future climate change on maize yield.

Nitrogen accumulation and nitrogen substitution effect of maize under straw returning with continuous cropping

<p id="C3">Crop straw resources in Northeast China are rich, but burning and discarding are serious, and nutrient utilization rate is very low. We explored the feasibility of the substitution of straw returning to nitrogen fertilizer and its effects on nitrogen accumulation under continuous cropping in cold region. A frame culture and continuous positioning experiment was carried out in the experimental site of Northeast Agricultural University from 2017 to 2019, with ¹⁵N labeled urea. A three-factor split-plot design was adopted in this experiment, the main plot was straw returning method with no straw returning (S0) and straw returning (S1), and the sub-plot was nitrogen application levels with 0 (N0), 175 (N1), and 350 (N2) kg hm^-2. Two application methods were set for each fertilizer application amount, one ratio of base fertilizer and top dressing applied was 1:1, and the other ratio of base fertilizer and top dressing applied was 1:0. The results were as follows: When the straw returning amount was 12 t hm^-2, the returning straw could replace 36.8 kg hm^-2 pure nitrogen. The average amount of maize straw was 46.50 million tons in Heilongjiang Province from 2017 to 2019, and straw returning could replace 142,700 tons pure nitrogen. The replace amount of pure nitrogen in the ratio of base fertilizer and top dressing (1:1) was 26.88% higher than that in 1:0. Straw returning was negatively correlated with nitrogen use efficiency in maize. The average nitrogen use efficiency of maize in S0 treatment was 6.09% higher than S1 treatment, and the yield of S1 treatment was 4.66% higher than S0 treatment when the urea application amount was 350 kg hm^-2 (161 kg hm^-2 pure nitrogen). The highest yield of maize was 268.22 g frame^-1 in the treatment of straw returning and topdressing with commonly fertilizer applied in local agriculture. In conclusion, the nitrogen substitution effect was remarkable under maize straw returning in Northeast China. Long-term combined application of crop straw and nitrogen fertilizer significantly improved the biomass, yield, and nitrogen accumulation of maize, which was a cultivation mode for increasing yield and efficiency of maize in Northeast China.

Organic substitutions improve soil quality and maize yield through increasing soil microbial diversity

Organic substitution is beneficial to sustainable agricultural development. In order to determine the proper fertilization strategy, it is necessary to evaluate the effects of partial substitution of nitrogen fertilizer with organic amendments on soil quality and crop yield, as well as their decisive factors. A five-year organic substitution field experiment was set up to investigate the effects of partial substitution of chemical fertilizer with stover, cattle manure and biochar on soil quality, soil microbial and nematode diversities and crop yield in a maize (Zea mays L.) field of Northeast China. Our results showed that organic substitutions increased soil quality and manure substitution increased maize yield through changing the composition and functional group of soil biota. Bacteria played important roles in determining the maize yield, but the beneficial effects were contingent on the different types of organic substitution. Stover substitution improved soil quality through increasing bacterial diversity but may lead to the competition of nitrogen between microorganisms and crops. Compared with conventional fertilization, manure substitution provided resources with suitable C/N ratio (6.82) and resulted in the higher maize yield, but the soil quality improvement was weaker under manure substitution than under stover substitution. Biochar substitution reduced the relative abundance of plant-parasitic nematodes but caused an increasing of potential pathogenic fungi for maize. Comprehensively, stover substitution is the most promising fertilization regime for maize in Northeast China from the perspective of soil quality and soil biodiversity.

Evaluation of AquaCrop model performance under mulched drip irrigation for maize in Northeast China

Establishing scientific management and grain production strategies through crop models is an important means to ensure stable and increased food production. To explore the performance of the AquaCrop model for simulating maize growth under mulched drip irrigation in Northeast China, the model was calibrated and verified locally based on three years of measured field data. The simulation effects of canopy cover (CC), total soil-water (TSW), aboveground biomass, crop evapotranspiration (ETC) and grain yield under mulched or nonmulched drip irrigation treatments with different water stress conditions were evaluated and compared. The study found the model had a good simulation effect on CC excluding the rainfed treatment, the root mean square error (RMSE) was <15.2%. The simulated values of TSW and ETc were quite different from those observed in the field. The TSW content was generally underestimated in the middle and late stages of maize growth, with RMSE values ranging from 12.8 to 60.7 mm. The simulated ETC values were generally high, and the prediction error of some treatments exceeded 20%. The model simulated the aboveground biomass and yield well in the calibration year (2016) and the RMSE values were 0.9–2 t/ha and 0.8 t/ha, respectively, but the simulation performance of predicting yield declined in the verification year, and the prediction error exceeded 20%. Compared with the mulched treatments, the model had a better simulation effect on the nonmulched treatments. In general, the simulation of soil moisture under drip irrigation needs to be improved, and the larger overestimation of transpiration and the lower underestimation of evaporation caused to overestimate the maize ETc. It is recommended to improve the simulation of mulched drip irrigation to ensure model applicability in the region of interest.

First Detection of Ditylenchus destructor Parasitizing Maize in Northeast China

Maize is one of the most important crops in the world. Heilongjiang province has the largest maize area in China. Plant-parasitic nematodes are important agricultural pests, which cause huge economic losses every year and have attracted global attention. Potato rot nematode Ditylenchus destructor is a plant-parasitic nematode with a wide range of hosts and strong survival ability in different environments, which brings risks to agricultural production. In 2020, D. destructor was detected in seven maize fields in Heilongjiang province. Morphological identification and molecular approach were used to characterize the isolated D. destructor. The observed morphological and morphometric characteristics were highly similar and consistent with the existing description. The DNA sequencing on the D2/D3 region of the ribosomal DNA 28S and the phylogenetic analysis showed that D. destructor population obtained from maize and other isolates infesting carrot, sweet potato, and potato were in subclade I supported by a 96% bootstrap value. Additionally, the phylogenetic analysis of the ITS rRNA gene sequence further indicated that this D. destructor population from maize clustered in a clade I group and belonged to ITS rRNA haplotype C. An inoculation experiment revealed that D. destructor was pathogenic on the maize seedlings in pots and caused the disease symptoms in the stem base of maize seedlings. This is the first report of D. destructor causing stem rot of maize in Heilongjiang province, and contributes additional information on disease control and safe production of maize in the region.

Building a new machine learning-based model to estimate county-level climatic yield variation for maize in Northeast China

China is one of the top maize exporting countries in the world. In China, maize is the most important staple food crop, and Northeast China is one of the main maize-growing regions. Regional maize production in Northeast China is critical for national or even global food security. In order to take preventive measures in combating the potential impacts of climate change on maize yield, it is imperative to evaluate historical climatic maize yield variation at finer scales in Northeast China. Previous scholars have achieved some good results in crop yield projection by using machine learning methods. However, climatic crop yield variation has rarely been addressed by considering the geographical factors (i.e., elevation, latitude, and longitude) of the meteorological stations used. In this study, based on 18 climatic elements during the period of 2003–2016, we compared the performance of three machine leaching methods, including neural network, support vector machine, and random forest, with multiple linear regression in evaluating climatic maize yield variation. Overall, machine learning methods are superior to traditional multilinear regression, particularly the neural network (with an R2 of 0.43 and an annual average MAE of 1.22 ton·ha−1). We selected the best machine learning methods and used the Bayesian method to integrate them as a new model. The Bayesian method reduced the evaluation error (i.e., RMSE and MAE) and improved the estimation accuracy. By addressing the uncertainty in the meteorological stations, our newly built model could be extended to other regions for evaluating climatic crop yield variation.

Influence of Tillage on the Mollisols Physicochemical Properties, Seed Emergence and Yield of Maize in Northeast China

Tillage practices are critical for sustaining soil quality necessary for successful crop growth and productivity, but there are only few studies for strip tillage (ST) in the Mollisols region of Northeast China at present. A long-term (≥10-year) study was carried out to investigate the influence of within the tilled row (IR) and between rows (BR) in ST (10-year), conventional tillage (CT, 14-year) and no tillage (NT, 14-year) treatments on soil physicochemical properties. Soil samples were taken in May of 2019 at 0–5, 5–10, 10–20 and 20–30 cm depths and used to analyze bulk density (BD), soil aggregate distribution and stability, and soil organic carbon (SOC). Meanwhile, our study also explored the differences in seed emergence, soil moisture, and temperature during the seed emergence period, and yield of maize (Zea mays L.) among the different treatments. Similar soil properties were observed between ST-BR and NT, which showed they had a significantly greater BD, &gt;0.25 mm water stable aggregate content (WR0.25) (especially in the amount of &gt;2 mm and 1–2 mm size proportion), aggregate stability, and SOC than ST-IR and CT-IR at a depth of 0–20 cm. By improving soil conditions of seedbed, ST-IR and CT-IR increased soil temperature above NT by 1.64 °C and 1.80 °C, respectively, and ST-IR had a slight greater soil moisture than CT-IR in the top 10 cm layer during the seed emergence period. Late maize seed emergence was observed NT in than ST-IR and CT-IR and the average annual yields in ST were slightly greater than NT and CT, but the differences were not significant. Our results also showed that CT-BR had a poor soil structure and lower SOC than other treatments at 0–30 cm depth. We conclude from these long-term experimental results that ST could improve soil water-heat conditions to promote seed germination, maintain soil structure, and increase the maize yield and it should be applied in the Mollisols region of Northeast China.

Responses of Root Characteristic Parameters and Plant Dry Matter Accumulation, Distribution and Transportation to Nitrogen Levels for Spring Maize in Northeast China

Improving nitrogen use efficiency is a significant scientific problem to be solved. Two maize hybrids JD27 (Jidan 27) and SD19 (Sidan 19) were selected to study the effects of nitrogen levels on root characteristic parameters and plant dry matter accumulation, distribution and transportation. We set five different nitrogen levels, which were nitrogen deficiency (000N), low nitrogen (075N), medium nitrogen (150N), high nitrogen (225N) and excessive nitrogen (300N). The results showed that the root length and root surface area of JD27 were significantly higher than those of SD19 under 075N. With the increase of nitrogen levels, the root difference among varieties gradually decreased. The root length, projection area, total surface area and total volume reached the maximum values at silking stage. The average root diameter kept stable or decreased slowly with the growth stage. The dry matter accumulation of JD27 was higher than that of SD19 at all growth stages. Increasing the amount of nitrogen fertilizer can promote the transport of dry matter to grain and improve dry matter transport efficiency after anthesis. Under the treatment of medium and high nitrogen fertilizer, maize was easy to obtain a higher yield, but excessive nitrogen fertilizer inhibited the increase of yield. This study provides theoretical and practical guidance for maize production techniques.

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.