Causes of maize density loss in farmers’ fields in Northeast China

Increasing plant density is an effective and important way to reduce maize yield gaps in Northeast China. However, the fact is that a significant plant density gap exists between optimum plant density and actual plant density in farmers’ fields.To quantify the density gap between planned planting density and final harvest plant density(HPD), we studied 60 farmers’ fields on three types of soil for three crop seasons from 2015 to 2017 by measuring their plant-plant distance, actual seedlings density(ASD), final HPD and yield. We also explored the potential causes of density loss by digging the places where the seedlings were missing for two consecutive years in 2016–2017. Results show that the three-year average HPD in farmers’ fields was 59 699 plants ha^–1, which was significantly lower than the planned density, including both the machine setting density(MSD;67 962 plants ha^–1) and theoretical plant density(TPD;67 467 plants ha^–1). No significant difference was found in HPD between years and soil types. However, for MSD and TPD, the average value in 2015 was significantly higher than that in 2016 and 2017. No significant difference between soil types was observed. Furthermore,the results from 2016 till 2017 indicated that a lack of seeds in the soil, a failure to germinate due to low-quality seeds,and a lack of seedlings breaking out of the soil due to environmental problems explained approximately 60.88, 10.33 and 28.80% of density loss, respectively. According to our survey, 63% of farmers did not know their own TPD and HPD, and 54% of farmers did not know the density loss. Therefore, we argue that farmers’ limited knowledge of density and density loss is an urgent problem that needs to be solved in maize production. These observations will be useful for determining best management practices for maize production and for providing helpful suggestions for machine improvement.

Developing sustainable summer maize production for smallholder farmers in the North China Plain: An agronomic diagnosis method

With an increasing population and changing diet structure, summer maize is increasingly becoming an important energy crop in China. However, traditional farmer practices for maize production are inefficient and unsustainable. To ensure food security and sustainable development of summer maize production in China, an improved, more sustainable farmer management system is needed. Establishing this system requires a comprehensive understanding of the limitations of current farming practice and the ways it could be improved. In our study, 235 plots from three villages in the North China Plain(NCP) were monitored. Maize production on farms was evaluated;our results showed that the maize yield and nitrogen partial factor productivity(PFPN) were variable on smallholder farms at 6.6–13.7 t ha^–1 and 15.4–88.7 kg kg^–1, respectively.Traditional farming practices also have a large environmental impact(nitrogen surplus:–64.2–323.78 kg ha^–1). Key yield components were identified by agronomic diagnosis. Grain yield depend heavily on grain numbers per hectare rather than on the 1 000-grain weight. A set of improved management practices(IP) for maize production was designed by employing a boundary line(BL) approach and tested on farms. Results showed that the IP could increase yield by 18.4% and PFPN by 31.1%, compared with traditional farmer practices(FP), and reduce the nitrogen(N) surplus by 57.9 kg ha^–1. However,in terms of IP effect, there was a large heterogeneity among different smallholder farmers’ fields, meaning that, precise technologies were needed in different sites especially for N fertilizer management. Our results are valuable for policymakers and smallholder farmers for meeting the objectives of green development in agricultural production.

Factors influencing hybrid maize farmers' risk attitudes and their perceptions in Punjab Province,Pakistan

Hybrid maize farmers have to face diverse kinds of climate, biological, price and financial risks. Farmers＇ risk perceptions and risk attitudes are essential elements influencing farm operations and management decisions. However, this important issue has been overlooked in the contemporary studies and therefore there is a dearth of literature on this important issue. The present research is therefore, an attempt to fill this gap. This study aims to quantify hybrid maize farmers＇ perceptions of disastrous risks, their attitudes towards risk and to explore the impacts of various farm and farm household factors on farmers＇ risk attitudes and risk perceptions. The present study is conducted in four hybrid maize growing districts of Punjab Province, Pakistan, using cross-sectional data of 400 hybrid maize farmers. Risk matrix and equally likely certainty equivalent （ELCE） method are used to rank farmers＇ perceptions of four catastrophic risk sources including climate, biological, price and financial risks and to investigate farmers＇ risk aversion attitudes, respectively. Furthermore, probit regression is used to analyze the determinants affecting farmers＇ risk attitudes and risk perceptions. The results of the study showed that majority of farmers are risk averse in nature and perceive price, biological and climate to be potential sources of risks to their farm enterprise. In addition, analysis divulges that distance from farm to main market, off-farm income, location dummies for Sahiwal and Okara, age, maize farming experience, access to extension agent, significantly （either negatively or positively） influence farmers＇ risk attitudes and risk perceptions. The study delivers valuable insights for farmers, agricultural insurance sector, extension services researchers and agricultural policy makers about the local understanding of risks to hybrid maize crop in developing countries, like Pakistan, and have implications for research on farmers＇ adaptation to exposed risks.

Choice of Adaptation Strategies to Climate Variability among Smallholder Farmers in the Maize Based Cropping System in Namutumba District, Uganda

Smallholder farmers in Namutumba district draw on a combination of adaptation strategies to respond to effects of climate variability. However, there is limited scholarly evidence and explanation that has been conducted on the factors that influence the choice of alternative sets of strategies that smallholder farmers use in response to climate variability specific stress and literature that disentangles climatic stressors specific adaptation options. A multi-stage sampling procedure was employed to select the study area and household respondents. The study used cross-sectional research design to collect both quantitative and qualitative data. Household data was collected from 160 respondents with a structured questionnaire supported by key informant interviews. Multinomial logit modeling (MNL) was used to determine the relative influence of selected household socio-demographic factors on the choice of adaptation strategies against the dry spell. Principal Components Analysis (PCA) was used to create weighted adaptation index for categorizing various similar adaptation strategies. In order to respond to the impact of climate variability stresses, smallholder farmers have adapted growing drought-resistant crops (12.2%), extension of the agricultural frontier into wetlands during the dry spells (37%), whereas use of crop rotation (9.8%) is the most dominant strategies used to manage pest and diseases, similarly soil and water conservation (15.3%) and climate-smart planning basin (11%) are the most dominant adaptation strategies use to manage flood. Empirical results from multinomial logit modeling showed that predictor variables gender, level of education, years of farming, house size, access to credit, and own radio have a significant influence on the choice of adaptation strategies with differences significant level during the dry spell. The study recommends that future policies should focus on strengthening the existing extension training package, strengthening the existing farmer’s groups and cooperatives, encouraging informal social networks in order to boost smallholder farmers’ adaptation to climate variability.

Farmers' seed choice behaviors under asymmetrical information: Evidence from maize farming in China

the financial support of the National Social Science Foundation of China （14ZDA038）;the National Natural Science Foundation of China （71222302;71373255;71573133）;the Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences （2012RC102）

Effects of Farmers’ Practices on Maize (<i>Zea mays</i>) Contamination by Potential Aflatoxigenic Fungi and Aflatoxin in Benue State, Nigeria

Aflatoxin associated with a number of cereals and legumes is estimated to increase the chances of developing primary liver cancer in 152.7 and 61.1 cancer/year/100,000 population of infants and children, respectively in Nigeria. This study was carried out to assess the implications of some agronomic practices on the infestation of aflatoxigenic fungi and total aflatoxin in maize produce in Benue State. Two maize sample types (Pre-harvest and Post-harvest) collected from 3 locations in Benue State were cultured on Sabouraud dextrose agar for fungi isolation and identification. Moisture content and total aflatoxin concentration were determined (ELISA method) in both pre-harvest oven dried and farmer’s post-harvest sun dried samples. Information on agronomic practices was obtained with the aid of questionnaire. T-test and analysis of variance (ANOVA) were used to analyze the data with confident levels set at 95&#37;. Overall, 5 mould genera were identified: Aspergillus (44.0&#37;), Fusarium (24.44&#37;), Botryodiplodia (17.78&#37;), Rhizopus (15.56&#37;) and Penicillium (4.44&#37;). Moisture content of oven dried samples was significantly less than that of farmers sun dried samples (t = 10.45, P < 0.001). Similarly, a significant difference in total aflatoxin concentration was recorded between farmers sun dried and oven dried samples (t = 2.37, P = 0.03). Half of the farmer’s sun dried samples had aflatoxin concentration above the recommended EU (4 ug/Kg) limit, but none of the pre-harvest oven dried samples exceeded EU limits. Maize samples from fertilized farms were more likely than non-fertilized farms to have higher aflatoxin concentration (P = 0.002). Similarly, Maize seeds purchase from the open market were more likely than seeds from previous harvest to be contaminated with aflatoxin (P = 0.003). The study advocates rapid drying of timely harvested maize so as to reduce or stop the action of heavy field fungi contaminants as well as aflatoxin accumulation.

The Impact of Climate Change on Maize Yield and Farmers' Adaptation Options:Evidence from Three Provinces of China

This paper tries to answer the question that whether farmers can adjust better to climate change in the short-term than in long-term by using panel data models and long difference models respectively.We find that short term weather shocks are less detrimental to maize yield than the long-term climate changes,which can be seen as the evidences of adaptations.For adaptation options,we find farmers choose to decrease maize planting area or enlarge the irrigation inputs to cope with the increase of extreme heat days;when there are more precipitations,farmers will increase the input of fertilizer or labor.

Evaluation of District-Based Indigenous Farmers’ and Researchers’ Fertilizer Application for Optimal Maize Production

Most research-based fertilizer inputs proposed for small scale farmers to increase their productivity do not achieve the required results and should consider indigenous practices. This study evaluates the practices of nutrient fertilizer input by farmers and researchers and relates them to their corresponding yields and profit so as to establish the appropriateness of the practices in 13 districts of the Northern regions of Ghana. Soil nutrients assessment of Nitrogen (N), Phosphorus (P) and Potassium (K) contents used to evaluate the soil NPK status was based on previous studies. Data on fertilizer application by farmers and researchers were obtained from the Savanna Agricultural Research Institute (SARI). The amount of N, P and K fertilizer input in 13 Districts and its associated maize grain yields by both farmers (89) and researchers were calculated and compared using two-sample t-test. The t-test results indicated that average amount of fertilizer input by researchers was significantly (p < 0.05) higher than the average amount of fertilizer input by the smallholder farmers, but the high fertilizer input did not significantly (p = 0.74) increase researchers’ maize yields and profits in all 13 study districts grouped together, but there was maize increment in only eight districts. On the average, farmers from five districts applied low fertilizer and recorded low yields. However, when researchers increased quantities of fertilizer applied in these five districts, yield significantly (p < 0.05) increased. The outcome showed that smallholder farmers in these five districts could increase maize yields by 36% in the region should they adopt the maize production strategy by the researchers. The study concluded that, for best options, recommended fertilizer doses to enhance maize yields should consider district-specific farmers’ practices and soil NPK status. The study could enable better implementation of location-based nutrient recommendation in the Northern Region of Ghana.

Maize Storage and Consumption Practices of Farmers in Handeni District, Tanzania: Corollaries for Mycotoxin Contamination

In Tanzania, maize is the main complementary food for infants and primary school children. Dietary exposure to mycotoxins through complementary foods by Tanzanian infants is of concern. The maize storage and consumption practices of farmers in Handeni District, Tanzania and their implications for mycotoxin contamination of maize flour were investigated. A convenient sample of 60 farmers in Seza Kofi and Kwabojo villages in Mgambo and Ndolwa wards were surveyed. The majority of farmers (95%) stored their maize in the house using the roofing and sack methods. Most farmers (67%) did not visually or mechanically sort defective maize kernels before storage. In both villages, the most important storage problems reported by the farmers were rodents and insects. Forty two percent of the farmers surveyed indicated that they consumed dehulled maize, while 35 and 12% consumed non-dehulled and mixed (dehulled and non-dehulled), respectively. The preponderance of storage practices described was unfavorable to mycotoxin reduction in stored maize. It is therefore recommended that appropriate, area-specific farmer training regarding recommended storage practices including storage methods, effective management of storage pests and healthy maize preparation and consumption practices be conducted. Additionally, further research on maize storage and consumption practices for Tanzania is needed.

Evaluation of Evolution and Diversity of Maize Open-Pollinated Varieties Cultivated under Contrasted Environmental and Farmers’ Selection Pressures: A Phenotypical Approach

OPVs (open pollinated varieties) of cross pollinated crops are genetically heterogeneous and therefore likely to evolve over generations, under natural and human selection, which gives them a strong potential for organic and low input farming. OPVs of maize were cultivated and selected by different farmers in France and Italy for 2 generations. The third year, they were phenotypically evaluated for evolution, adaptation and level of diversity (estimated with Nei index) across evolution in a combined on farm and on station experimentation. The results showed that the varieties evolved and even adapted over 2 generations only (especially on maturity traits) but conserved their identity (no evolution of ear morphological traits). They all conserved their diversity, which demonstrated the pertinence of farmers’ selection (it is not a bottleneck). These results suggested that the genetically heterogeneous nature of OPVs is an asset for farmers because they can adapt these varieties to specific local conditions and production objectives. Therefore, farmer OPVs should receive more support through social and regulatory recognition, as well as further interest from research.

Economic Analysis of Maize Production Among Irrigation Farmers in Orire Local Government Area, Oyo State, Nigeria

This study analyzed economic value of maize production among irrigation farmers in Orire Local Government, Oyo State, Nigeria. The objectives of this study are to： identify the most important resources used by the farmers in maize production; estimate the production function in order to determine the economic efficiency of different resource used in maize production. The data were obtained through a survey of 80 farmers, comparing farmers using pump and those using shadoof methods of irrigation for maize cultivation. Simple descriptive statistics and Cobb-Douglas production function used revealed that fertilizer was underutilized. The marginal productivity of labour was positive but lower than the average acquisition cost for both techniques of irrigation. Both primary and secondary data were used for the study. Well structured questionnaire and interview schedule were used as approaches to collect data from respondents. The results showed that irrigation users were small-scale farmers, cultivating small hectare of land using simple farm tools, practicing pump irrigation or calabash system. Regression analysis revealed that land, labour purchase inputs had a positive relationship with the output of the enterprises, the linear programming analysis revealed that opportunities existed for increasing profit through resources re-organization, budgetary analysis was used to show that irrigation was profitable.

Optimizing Fertilizer Use by Smallholder Farmers and Economic Returns to Maize in Semi-arid Niger

Maize （Zea mays L.） is an important food crop in Niger, but low and irregular rainfall combined with sandy soils having low fertility level limit productivity. A two-year study was conducted at Institut National de Recherche Agronomique du Niger （INRAN） stations in Tarna/Maradi and Bengou/Gaya in 2014 and 2015 in order to evaluate maize agronomic and economic fertilizer use efficiency. The experimental design was a randomised complete block design （RCBD） with three replications. Results indicate higher effect of fertilizer in 2015 compared to 2014. At low N rates 20 kg N/ha and 40 kg N/ha, application of 20 kg P/ha increased maize grain yield across locations and years. The highest agronomic efficiency of N （AEN） was recorded with 60 kg N/ha in 2015 at Bengou and Tarna with 9.65 kg and 14.05 kg grain yield per kg of applied N, respectively. At Tarna, the low N rates of 20 kg N/ha and 40 kg N/ha recorded important AEN of more than 12 kg yield increases per kg of applied N. The highest rainfall use efficiency （RUE） of 6.13 kg/year/mm was obtained with application of 80 kg/ha N, 0 kg/ha P and 40 kg/ha N, 20 kg/ha P in 2015 at Tarna. Without P, the highest value cost ratio （VCR） value of 4.31 was recorded at Tarna in 2015 with 60 kg/ha N, and the lowest value of 0.08 at Bengou in 2014 with 20 kg/ha N. Based on VCR and RUE derived from this study, the optimal fertilizer recommendation for maize in the semi-arid conditions of Niger could be 40 kg/ha N, 20 kg/ha P and 0 kg/ha K.

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.

Farmer's Adoption of Improved Nitrogen Management Strategies in Maize Production in China: an Experimental Knowledge Training

Chemical fertilizer plays an important role in increasing food production in China. Nevertheless, excessive nitrogen fertilizer use in China has resulted in severe environmental problems. The goal of this paper is to examine the impacts of an improved nitrogen management （INM） training experiment on farmers＇ chemical nitrogen （N） use behaviors in maize production in China. Based on household data collected from 813 maize farmers in Shandong, China, this study finds that while INM training can significantly reduce farmers＇ N fertilizer use, an INM training is not sufficient to change farmer＇s practices significantly, and farmers only partially adopted the recommended INM. This study reveals that China faces challenges to transform its agriculture to a low-carbon one. The research also sheds light on China＇s extension system and future technologies in meeting the objectives of reducing the excessive nitrogen fertilizer use in agricultural production.

ZmbZIP27 regulates nitrogen-mediated leaf angle by modulating lignin deposition in maize

In grain crops such as maize(Zea mays),leaf angle(LA)is a key agronomic trait affecting light interception and thus planting density and yield.Nitrogen(N)affects LA in plants,but we lack a good understanding of how N regulates LA.Here,we report that N deficiency enhanced lignin deposition in the ligular region of maize seedlings.In situ hybridization showed that the bZIP transcription factor gene ZmbZIP27 is mainly expressed in the phloem of maize vascular bundles.Under N-sufficient conditions,transgenic maize overexpressing ZmbZIP27 showed significantly smaller LA compared with wild type(WT).By contrast,zmbzip27_(ems)mutant showed larger LA under both N-deficient and N-sufficient conditions compared with WT.Overexpression of ZmbZIP27 enhanced lignin deposition in the ligular region of maize in the field.We further demonstrated that ZmbZIP27 could directly bind the promoters of the microRNA genes ZmMIR528a and ZmMIR528b and negatively regulate the expression levels of ZmmiR528.ZmmiR528 knockdown transgenic maize displayed erect architecture in the field by increasing lignin content in the ligular region of maize.Taken together,these results indicate that ZmbZIP27 regulates N-mediated LA size by regulating the expression of ZmmiR528 and modulating lignin deposition in maize.

The transcription factor ZmNAC84 increases maize salt tolerance by regulating ZmCAT1 expression

Salt stress severely affects plant growth and yield.The transcription factor NAC plays a variety of important roles in plant abiotic stress,but we know relatively little about the specific molecular mechanisms of NAC in antioxidant defense.Here,our genetic studies reveal the positive regulation of salt tolerance in maize by the transcription factor ZmNAC84.Under salt stress,overexpression of ZmNAC84 in maize increased the expression of ZmCAT1,enhanced CAT activity,and consequently reduced H_(2)O_(2) accumulation,thereby improving salt stress tolerance in maize.Whereas RNA interference-mediated knockdown of ZmNAC84 produced the opposite effect.Subsequently,we found that ZmNAC84 directly binds to and regulates the expression of the ZmCAT1 promoter,and the hybridized material also demonstrated that ZmCAT1 is a downstream target gene of ZmNAC84.In addition,phenotypic and biochemical analyses indicated that ZmCAT1 positively regulated salt tolerance by regulating H_(2)O_(2) accumulation under salt stress.Taken together,these results reveal the function of ZmNAC84 in regulating ZmCAT1-mediated antioxidant defense in response to salt stress in plants.

Manure substitution improves maize yield by promoting soil fertility and mediating the microbial community in lime concretion black soil

Synthetic nitrogen(N)fertilizer has made a great contribution to the improvement of soil fertility and productivity,but excessive application of synthetic N fertilizer may cause agroecosystem risks,such as soil acidification,groundwater contamination and biodiversity reduction.Meanwhile,organic substitution has received increasing attention for its ecologically and environmentally friendly and productivity benefits.However,the linkages between manure substitution,crop yield and the underlying microbial mechanisms remain uncertain.To bridge this gap,a three-year field experiment was conducted with five fertilization regimes:i)Control,non-fertilization;CF,conventional synthetic fertilizer application;CF_(1/2)M_(1/2),1/2 N input via synthetic fertilizer and 1/2 N input via manure;CF_(1/4)M_(3/4),1/4 N input synthetic fertilizer and 3/4 N input via manure;M,manure application.All fertilization treatments were designed to have equal N input.Our results showed that all manure substituted treatments achieved high soil fertility indexes(SFI)and productivities by increasing the soil organic carbon(SOC),total N(TN)and available phosphorus(AP)concentrations,and by altering the bacterial community diversity and composition compared with CF.SOC,AP,and the soil C:N ratio were mainly responsible for microbial community variations.The co-occurrence network revealed that SOC and AP had strong positive associations with Rhodospirillales and Burkholderiales,while TN and C:N ratio had positive and negative associations with Micromonosporaceae,respectively.These specific taxa are implicated in soil macroelement turnover.Random Forest analysis predicted that both biotic(bacterial composition and Micromonosporaceae)and abiotic(AP,SOC,SFI,and TN)factors had significant effects on crop yield.The present work strengthens our understanding of the effects of manure substitution on crop yield and provides theoretical support for optimizing fertilization strategies.

Identification, pathogenicity, and fungicide sensitivity of Eutiarosporella dactylidis associated with leaf blight on maize in China

Maize(Zea mays L.) is an economically vital grain crop that is cultivated worldwide. In 2011, a maize foliar disease was detected in Lingtai and Lintao counties in Gansu Province, China. The characteristic signs and symptoms of this disease include irregular chlorotic lesions on the tips and edges of infected leaves and black punctate fruiting bodies in dead leaf tissues. Given favourable environmental conditions, this disease spread to areas surrounding Gansu. In this study, infected leaves were collected from Gansu and Ningxia Hui Autonomous Region between 2018and 2020 to identify the disease-causing pathogen. Based on morphological features, pathogenicity tests, and multilocus phylogenetic analysis involving internal transcribed spacer(ITS), 18S small subunit rDNA(SSU), 28S large subunit rDNA(LSU), translation elongation factor 1-alpha(TEF), and β-tubulin(TUB) sequences, Eutiarosporella dactylidis was identified as the causative pathogen of this newly discovered leaf blight. Furthermore, an in vitro bioassay was conducted on representative strains using six fungicides, and both fludioxonil and carbendazim were found to significantly inhibit the mycelial growth of E. dactylidis. The results of this study provide a reference for the detection and management of Eutiarosporella leaf blight.

Dynamics and genetic regulation of macronutrient concentrations during grain development in maize

Nitrogen(N), phosphorus(P), and potassium(K) are essential macronutrients that are crucial not only for maize growth and development, but also for crop yield and quality. The genetic basis of macronutrient dynamics and accumulation during grain filling in maize remains largely unknown. In this study, we evaluated grain N, P, and K concentrations in 206 recombinant inbred lines generated from a cross of DH1M and T877 at six time points after pollination. We then calculated conditional phenotypic values at different time intervals to explore the dynamic characteristics of the N, P, and K concentrations. Abundant phenotypic variations were observed in the concentrations and net changes of these nutrients. Unconditional quantitative trait locus(QTL) mapping revealed 41 non-redundant QTLs, including 17, 16, and 14 for the N, P, and K concentrations, respectively. Conditional QTL mapping uncovered 39 non-redundant QTLs related to net changes in the N, P, and K concentrations. By combining QTL, gene expression, co-expression analysis, and comparative genomic data, we identified 44, 36, and 44 candidate genes for the N, P, and K concentrations, respectively, including GRMZM2G371058 encoding a Doftype zinc finger DNA-binding family protein, which was associated with the N concentration, and GRMZM2G113967encoding a CBL-interacting protein kinase, which was related to the K concentration. The results deepen our understanding of the genetic factors controlling N, P, and K accumulation during maize grain development and provide valuable genes for the genetic improvement of nutrient concentrations in maize.

Effects of drip and flood irrigation on carbon dioxide exchange and crop growth in the maize ecosystem in the Hetao Irrigation District,China

Drip irrigation and flood irrigation are major irrigation methods for maize crops in the Hetao Irrigation District,Inner Mongolia Autonomous Region,China.This research delves into the effects of these irrigation methods on carbon dioxide(CO_(2))exchange and crop growth in this region.The experimental site was divided into drip and flood irrigation zones.The irrigation schedules of this study aligned with the local commonly used irrigation schedule.We employed a developed chamber system to measure the diurnal CO_(2)exchange of maize plants during various growth stages under both drip and flood irrigation methods.From May to September in 2020 and 2021,two sets of repeated experiments were conducted.In each experiment,a total of nine measurements of CO_(2)exchange were performed to obtain carbon exchange data at different growth stages of maize crop.During each CO_(2)exchange measurement event,CO_(2)flux data were collected every two hours over a day-long period to capture the diurnal variations in CO_(2)exchange.During each CO_(2)exchange measurement event,the biological parameters(aboveground biomass and crop growth rate)of maize and environmental parameters(including air humidity,air temperature,precipitation,soil water content,and photosynthetically active radiation)were measured.The results indicated a V-shaped trend in net ecosystem CO_(2)exchange in daytime,reducing slowly at night,while the net assimilation rate(net primary productivity)exhibited a contrasting trend.Notably,compared with flood irrigation,drip irrigation demonstrated significantly higher average daily soil CO_(2)emission and greater average daily CO_(2)absorption by maize plants.Consequently,within the maize ecosystem,drip irrigation appeared more conducive to absorbing atmospheric CO_(2).Furthermore,drip irrigation demonstrated a faster crop growth rate and increased aboveground biomass compared with flood irrigation.A strong linear relationship existed between leaf area index and light utilization efficiency,irrespective of the irrigation method.Notably,drip irrigation displayed superior light use efficiency compared with flood irrigation.The final yield results corroborated these findings,indicating that drip irrigation yielded higher harvest index and overall yield than flood irrigation.The results of this study provide a basis for the selection of optimal irrigation methods commonly used in the Hetao Irrigation District.This research also serves as a reference for future irrigation studies that consider measurements of both carbon emissions and yield simultaneously.