Maize Cropland Research Articles

Quantifying the contribution of meteorological factors and plant traits to canopy interception under maize cropland

A thorough understanding of crop canopy interception is crucial for understanding the relationship between water management and agriculture in water-limited regions. The factors that influence the interception process, such as meteorological conditions and plant traits, are diverse and uncertain. We divided meteorological factors and plant traits into three groups: precipitation-related meteorological factors (including precipitation event factors and raindrop factors), non-precipitation-related meteorological factors (air temperature, relative humidity, wind speed, etc.) and plant traits (leaf area index (LAI) and mean leaf inclination angle). The contributions of groups and each variable were then quantified with respect to canopy interception. This study was based on data from 80 events over four years (2017–2020). Measurements were taken under maize (Zea mays L.) cropland located on the southern Loess Plateau. The canopy interception (Ic) was calculated as the difference between precipitation and the sum of throughfall and stemflow and all of Ic was assumed to be lost to evaporation in the study. Results showed that the cumulative Ic of the 80 events was 395.9 mm, accounting for 39.7% of the contemporaneous total precipitation, but the mean proportion of canopy interception during each precipitation event (Ic percentage) was greater at 57.6% because of the high interception percentage during light precipitation events (0–5 mm, totaling 37 events). Pearson correlations analysis revealed a significant positive correlation between Ic and precipitation-related meteorological factors (including precipitation amount, duration, raindrop diameter (D50), terminal raindrop velocity (UV) (p < 0.01) and intensity, average downward force (F0) (p < 0.05)), whereas there was a significant negative correlation between Ic percentage and precipitation-related meteorological factors (p < 0.01) because precipitation amount was more affected by precipitation-related meteorological factors. When the results of different groups were compared, precipitation event factors (amount, duration and intensity) and raindrop factors (D50, UV, F0,) made the highest contribution to explaining Ic (56.4%) and Ic percentage (28.3%), respectively. Both the unique effect and individual importance of plant traits to Ic and Ic percentage increased when considering the precipitation events which occurred close to the LAI measurement date. It is essential that short-term assessments are used if considering LAI in relation to Ic. Precipitation amount had the largest individual importance on Ic (30.2%, p < 0.01), whereas D50 was the analogous variable for Ic percentage (9.5%, p < 0.05). Our results confirmed that interception by the maize canopy accounts for an important portion of the total field water input. The data and information on the interception process presented in this study, should contribute to the understanding of the overall water balance in agroecosystem environments and improve knowledge of the interplay between agroecosystems and the environment.

Profile soil organic and inorganic carbon sequestration in maize cropland after long-term straw return

Promoting cropland carbon (C) sequestration through straw return has always been the focus of numerous studies. However, there is still a lack of comprehensive understanding of the straw return effects on soil organic carbon (SOC) and soil inorganic carbon (SIC) sequestration. Therefore, the present study aims to investigate the effects of long-term straw return on SOC and SIC sequestration across the 0–100 cm soil profile in the maize planting cropland in Northeastern China. The results showed an increasing trend in SOC contents in the 0–100 cm soil profile following long-term straw return, while significant decreases in SIC contents were observed in the surface (0–20 cm) and subsoil (20–60 cm) layers, respectively. In addition, the SOC stock increased significantly in the subsoil layer following long-term straw return, by an average value of 44%, which is higher than those observed in other soil layers. On the other hand, the SIC stock in the subsoil layer increased by an average value of 24% and decreased in the surface and under-subsoil layers by average values of 53% and 33%, respectively. Moreover, the exchangeable calcium contents were positively correlated with SOC and SIC stock, demonstrating the soil calcium contributes to SOC and SIC sequestration. The present study highlighted the importance of the subsoil layer for effective straw return strategies in cropland to promote SOC and SIC sequestration in croplands.

Comparison of three modified models in evapotranspiration and its components over a rainfed spring maize cropland on the Loess Plateau, China

Accurately estimated evapotranspiration (ET) and its components in the growing season of cropland are required to optimize agricultural practices and improve water use efficiency. In this study, we developed a modified Shuttleworth–Wallace (SWm) model, a modified Priestley-Taylor (PTm) model, and a modified dual crop coefficient (DKm) model based on the characteristics of a rainfed spring maize cropland on the Loess Plateau. The estimated ET and its components by the three models were compared with the measured ET and its components using an eddy covariance system and microlysimeters. The results indicated that the three models performed well in estimating the 30 min ET and daily ET and its components during the growing seasons of the rainfed spring maize field in 2015 and 2016. The diurnal course of the measured 30 min ET was closest to that of the estimated 30 min ET from the DKm model, and this model performed best to estimate 30 min ET with a regression coefficient (b0) of 1.01 (R2 = 0.89) in 2015 and 0.97 (R2 = 0.88) in 2016. According to statistical analysis, the PTm model outperformed the other two modified models on estimating daily ET with b0 of 0.97 (R2 = 0.89) and 0.94 (R2 = 0.89) and daily plant transpiration (Tp) with b0 of 1.07 (R2 = 0.93) and 1.11 (R2 = 0.93) during the both growing seasons. The performance of the three modified models on daily soil evaporation (Es) was not as good as that of daily ET and Tp, and the DKm model performed best to reproduce daily Es with a b0 of 0.91 (R2 = 0.37) and 0.88 (R2 = 0.54) in 2015 and 2016, respectively. As the PTm model required the fewest input variables among the three modified models, this model was finally recommended for rainfed spring maize on the Loess Plateau, China.

Application of humic acid and hydroxyapatite in Cd-contaminated alkaline maize cropland: A field trial

Soil quality is critical to the quality and safety of agricultural products, and remediation of heavy metal contaminated soils is an urgent task to be implemented. This study applied hydroxyapatite (HAP) and humic acid (HA) as remediation materials to Cd-contaminated alkaline cropland. Data on soil pH, electrical conductivity (EC), cation exchange capacity (CEC), soil organic matter (SOM), diethylenetriamine pentaacetic acid (DTPA) extraction, and improved BCR sequential extraction were obtained for different periods. The joint application of HAP and HA enhanced the soil's buffering capacity. During the experiment, treatment groups CK, H1, H2, H3, and H4 showed changes in pH of 0.29, 0.28, 0.21, 0.24, and 0.32, respectively, and changes in the conductivity of 341.4, 183.0, 133.1, 104.6 and 320.2 μS/cm. Soil organic matter had a positive effect on soil's effective phosphorus content. HAP and HA both reduced the BCFgrain/soil of Cd for the maize, but the impact of HA was more substantial (20.19 % reduction compared to CK). HA increased the yield of maize by 44.20 %. The combination of HA and HAP was recommended.

Response of the Fate of In-Season Fertilizer Nitrogen to Plastic Mulching in Rainfed Maize Croplands of the Loess Plateau.

As plastic mulching is widely used for maize production on Loess Plateau, study of the fate of fertilizer nitrogen (N) in rain-fed croplands is of great significance. Field experiments were conducted during 2015–2016 at a typical dry-land farm on the Loess Plateau, China. The stable isotope tracer technique was applied to analyze the effects of plastic mulching on the maize crop yield, N content in the grain, and mechanism of N uptake and utilization in maize plants with plastic mulch (PM) and without plastic mulch (CK) on the Loess Plateau. Maize yield, aboveground dry matter, grain N concentration, and N uptake in aboveground biomass for PM significantly increased, in addition to fertilizer nitrogen recovery and nitrogen production efficiency. Compared to CK, PM improved the total N uptake from the soil in the aboveground biomass by 16.39 and 27.75 kg ha−1 and fertilizer nitrogen recovery by 10.89 and 22.02 kg ha−1, respectively. Furthermore, PM increased in-season fertilizer N retention in the soil by 11.9–24.8 kg ha−1, and the uncountable fertilizer N decreased by approximately 33.8 kg ha−1 on average. In conclusion, PM simultaneously improved the maize yield and N utilization, which provides a scientific basis for nitrogen management in maize croplands.

Evapotranspiration and carbon exchange of the main agroecosystems and their responses to agricultural land use change in North China Plain

The North China Plain (NCP) plays an important role in food production while there is serious groundwater overexploitation in this area. The quantified relationship between the variation in evapotranspiration (ET) and net ecosystem CO2 exchange (NEE) and agricultural land use change in NCP remains unclear. In this study, based on the eddy covariance method, water balance method, and remote sensing data, ET and NEE variations were quantified and the impacts of agricultural land use change from 2002 to 2012 on regional ET and NEE variation were analyzed. The average ET and NEE of the winter wheat – summer maize cropland ecosystem were 714.2 mm yr-1 and − 534.3 gC m-2 yr-1, respectively. Correspondingly, the above values were 786.2 mm yr-1 and 667.5 gC m-2 yr-1 for the pear orchard ecosystem, and 778.6 mm yr-1 and 814.8 gC m-2 yr-1 for the vegetable field ecosystem, which had relatively high ET and ecosystem productivity. The average annual ET and NEE of the cotton field ecosystem were only 592.0 mm and − 351.3 gC m-2, respectively. Agricultural land area increased by 331.2 × 103 ha over 2002–2012, which was caused by the increasing land area of spring maize, forest/fruit trees, and vegetables. As a result, the ET and NEE of the agroecosystems in NCP increased by 25.6 × 108 m3 and − 257.9 × 104 tonC from 2002 to 2012, which are beneficial for carbon sequestration. However, the increase in carbon sink was at the cost of greater groundwater overexploitation due to increased regional water consumption. The planting of crops with high water consumption should be reduced as the surpluses of these agricultural products compared to the food demand in this region. These results are meaningful for reasonable planting structure adjustment of water-adaptive sustainable agricultural development in the NCP.

Comparison of water consumption for the conversion of croplands to orchards in dryland ecosystems

AbstractEvapotranspiration (ET) is the main ecological and soil water consumption process in terrestrial ecosystems. Previous studies have investigated ET partitioning across sites and plants; however, direct comparisons of water consumption before and after the transition from one crop to another are scarce. The variation in and proportion of ET and its subcomponents as well as the change in soil water storage (SWS) were compared in maize (Zea mays L.) croplands and apple (Malus domestica auct. non Borkh. cv. Fuji) orchards in four active (approximately May to September) and three inactive growth periods on the southern Loess Plateau, China. Soil water evaporation (Es) accounted for 36.3 and 37.7% of the total ET for cropland and orchard, respectively, in the active growth period. The canopy interception (Ic) significantly differed between cropland and orchard. The mean Ic/ET for cropland and orchard was 23.1 and 22.7%, respectively, in the active growth period, showing that the effects of Ic on ET partitioning should not be ignored. The mean ratio of transpiration (T) to ET for cropland was 2.8% less than that for orchard during the active growth period. The T/ET of cropland peaked twice in each active growth period. Precipitation (P) met the water consumption requirements of crop growth in the active growth period. The ET of cropland and orchard in the inactive growth period accounted for 29.4 and 31.8% of the ET for the hydrological year, respectively. These results help assess water consumption and soil sustainability under changes in crops in dryland agricultural ecosystems.

Effect of farming on the vegetation structure, soil properties and termite assemblages in the northern Congo Basin

AbstractThe growing human population requires vast amounts of supplies that are satisfied by a large agricultural expansion leading to alarming deforestation of tropical forests. Agriculture in the large part now is unsustainable as tropical soils are relatively nutrient poor, the amount of organic matter decreases fast and the soil invertebrates and microorganisms vanish over time. From a socio‐economic point of view, agroforestry is a sustainable alternative to slash‐and‐burn practices, but its impact on termites, major macroinvertebrates responsible for the organic matter turnover, is poorly understood. Furthermore, other vegetation layers besides tree canopy are rarely included in studies despite their strong effect on soil macrofauna. Thus, we investigated the impact of human activities in Southern Cameroon by analysing the biomass of termites, the soil properties, the vegetation structure at three different classes (trees, shrubs and herbs) and the amount of raw vegetal material along a land‐use gradient of primary forest ‐ secondary forest ‐ cocoa agroforestry ‐ maize cropland. Within each of the habitats, two independent areas of 1 ha each were laid out for samples collection. Our results show similar trends for all variables, with a reduction of organic carbon as well as available micronutrients, plant diversity and abundance and dead plant matter stocks along the land‐use intensification. The same trend is shown by the abundance and biomass of termites, best exemplified by the absence of soil‐feeding termites in the maize cropland. We thus recommend for support to nature‐friendly agroforestry systems preserving a large share of the original soil invertebrates.

Trade-offs between high yields and soil CO2 emissions in semi-humid maize cropland in northern China

Optimizing yields while reducing soil CO2 emissions in cropping systems has become the focus of agricultural study. To explore effective ways to achieve the balance, short-term field experiments (2018–2020) were conducted in North China Plain. Three replications of three-factor combinations of two tillage systems (i.e., no-tillage and conventional tillage), two straw management (i.e., no straw and straw mulch), and two nitrogen fertilization levels (i.e., medium nitrogen of 180 kg N ha1 and high nitrogen of 210 kg N ha1) were arranged in a randomized complete block design. It was discovered that soil CO2 emissions were mainly dominated by soil temperature. No-tillage decreased soil CO2 emissions by 7.3% than conventional tillage, straw mulch promoted soil CO2 emissions than no straw, and high fertilization increased CO2 emissions by 21.8% compared to medium fertilization. However, maize yields were not significantly affected by above treatments. The combinations of agricultural practices that achieved the highest maize yields were medium nitrogen in combination with straw mulch under no-tillage and conventional tillage. The combination of no-tillage, straw mulch, and medium nitrogen decreased soil CO2 emissions intensity by 11.5%. It was concluded that the combination of no-tillage, straw mulch amendment, and medium nitrogen achieved a balanced yields and soil CO2 emissions, which should be recommended for local farmers in North China Plain.

Pool complexity and molecular diversity shaped topsoil organic matter accumulation following decadal forest restoration in a karst terrain

Fast accumulation of soil organic matter (SOM) following forest restoration shifted from cropland has been widely reported, but how the pools and molecular composition change across soil aggregate fractions remains unclear. In this study, undisturbed topsoil (0–10 cm) samples were collected across a decadal chronosequence of forest stands (RL10, RL20 and RL40) restored for 10, 20 and 40 years following maize cropland (CL) abandonment in a karst terrain of Guizhou, Southwest China. SOM changes were explored using the size and density fractionation of water-stable aggregates, 13C isotopic signalling and biomarker analyses as well as 13C solid-state NMR assays. Compared to that of CL, SOM content was increased by 24%, 79% and 181%, mass proportion of macroaggregates increased by 136%, 179% and 250%, and particulate organic matter (POM) increased by 13%, 108% and 382%, respectively at RL10, RL20 and RL40. With biomarker analyses, the relative abundances of plant-derived organics (lignin, cutin, suberin, wax and phytosterols), mostly protected in aggregates, increased, while those of microbe-derived OC, predominantly mineral bound, decreased in response to prolonged forest restoration. Calculated as per the Shannon diversity index (H’), changes in SOM pool complexity and molecular diversity were parallel to the SOM accumulation trend. The pool size ratio of POM to MAOM (mineral-associated organic matter) and the molecular abundance ratio of PL (plant-derived lipids) to ML (microbe-derived lipids) appeared to be indicative of SOM accumulation following forest restoration. With prolonged forest restoration, the topsoil OM shifted from microbial MAOM dominance to plant-derived POM dominance. Furthermore, the great topsoil OM enhancement in restored forest stands was shaped by pool complexity and molecular diversity changes with the complex interactions among plant-microbial-mineral assemblages in the karst topsoil. Both the pool complexity and molecular diversity of SOM should be considered in addressing carbon sequestration with forest restoration concerning the functioning of soil ecosystems and services under global change pressures.

Comparison of Three Modified Models in Evapotranspiration and its Components Over a Rainfed Spring Maize Cropland on the Loess Plateau, China

Comparison of Three Modified Models in Evapotranspiration and its Components Over a Rainfed Spring Maize Cropland on the Loess Plateau, China

Comparison of Three Modified Models in Evapotranspiration and its Components Over a Rainfed Spring Maize Cropland on the Loess Plateau, China

Comparison of Three Modified Models in Evapotranspiration and its Components Over a Rainfed Spring Maize Cropland on the Loess Plateau, China

Effects of environmental conditions and leaf area index changes on seasonal variations in carbon fluxes over a wheat-maize cropland rotation.

Environmental conditions (EV) changes not only affect temporal variations in carbon fluxes directly, but affect them indirectly by impacting plant biotic traits. Investigating the extent of the effects of EV and biotic changes can help deepen our understanding of ecosystem carbon cycling. Therefore, we partitioned and quantified the contributions of EV and biotic changes' effects on seasonal variations in carbon fluxes (net ecosystem carbon exchange (NEE), and its components, i.e., gross ecosystem carbon exchange (GEE) and ecosystem respiration (RE)) in a (winter) wheat-(summer) maize rotation ecosystem from 2010 to 2012. A path analysis accompanied by Granger causality tests (GCTs), which filtered out several variables that were not causal for dependent variables, was used to calculate their respective contributions by integrating path coefficients. The seasonal variations in NEE, RE, and GEE were significantly and jointly affected by EV and the leaf area index (LAI) with R2 values ranging from 0.63 to 0.94 after the GCT. The path analysis indicated that the seasonal variations of carbon fluxes were dominated by the effects of EV changes (induced from varying EV for different fluxes, crops, and years), which contributed 60.7% (mean of two years), 64.5%, and 58.2% to wheat NEE, RE, and GEE, respectively, and 62.5%, 82.3%, and 58.1% to maize NEE, RE, and GEE, respectively. Overall, our study provided a new basis that future climatic changes may have important impacts on carbon exchanges in this rotation cropland.

Variations in seasonal and inter-annual carbon fluxes in a semi-arid sandy maize cropland ecosystem in China's Horqin Sandy Land.

Sandy cropland ecosystems are major terrestrial ecosystems in semi-arid regions of northern China's Horqin Sandy Land, where they play an important role in the regional carbon balance. Continuous observation of the CO2 flux was conducted from 2014 to 2018 using the eddy covariance technique in a sandy maize cropland ecosystem in the Horqin Sandy Land. We analyzed carbon fluxes (the net ecosystem exchange (NEE) of CO2, ecosystem respiration (Reco), and the gross primary productivity (GPP) and their responses to environmental factors at different temporal scales using Random Forest models and correlation analysis. We found that the sandy cropland was a carbon sink, with an annual mean NEE of -124.4 g C m-2 yr-1. However, after accounting for carbon exports and imports, the cropland became a net carbon source, with net biome production ranging from -501.1 to -266.7 g C m-2 yr-1. At a daily scale, the Random Forest algorithm revealed that photosynthetic photon flux density, soil temperature, and soil moisture were the main drivers for variation of GPP, Reco, and NEE at different integration periods. At a monthly scale, GPP and Reco increased with increasing leaf area index (LAI), so the maize ecosystem's carbon sequestration capacity increased with increasing LAI. At an annual scale, water availability (precipitation and irrigation) played a dominant role in explaining inter-annual variability of GPP and Reco. Affected by climate (e.g., precipitation) and field management (e.g., cultivation, irrigation), carbon fluxes differed greatly between years in the maize system.

Weed Responses to Crop Residues Management in a Summer Maize Cropland in the North China Plain

Crop residues management has great effects on weeds in croplands. To understand the weed responses to crop residues management and weeds impact on crop yield, a field trial with three crop residues management strategies has been conducted in the North China Plain since 2008. Weed community composition and structure across the species, morphological types, life forms, and community levels were investigated during 2019–2020. The results show that the field with crop residues retention significantly decreased weed density than that in the field with no crop residues retention. Furthermore, total crop residues retention significantly decreased weed density than half crop residues retention. Compared with no crop residues retention, the weed aboveground dry matter in the field with total and half crop residues retention significantly decreased. Meanwhile, the maize grain yield significantly increased, resulting from weeds decreased with crop residues retention on the field. Negative correlations were found between maize grain yield and the density and aboveground dry matter of monocotyledonous weeds. These findings indicate that long term crop residues retention under conventional tillage might be an effective agronomic practice to retard weed growth. However, the mechanism of crop residues retention on weed control is still needed to research.

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.

Effects of legume intercropping and nitrogen input on net greenhouse gas balances, intensity, carbon footprint and crop productivity in sweet maize cropland in South China

How to achieve greater crop productivity with lower greenhouse gas (GHG) emissions from limited farmland has been a hotspot of interest in global agricultural production. In this study, we analyzed the effects of legume intercropping and nitrogen (N) fertilizer level on net greenhouse gas balances (NGHGB), yield-based greenhouse gas emissions intensity (GHGI), carbon footprint (CF) and crop productivity in sweet maize cropland in South China based on a long-term field experiment during 2013–2018. Results demonstrated that the sweet maize/soybean intercropping pattern could improve crop productivity on the unit of arable land, but the yield advantage of the intercropping system was totally derived from the soybean. Accordingly, the intercropping pattern reduced the GHGI with significant difference compared to the sweet maize mono-cropping system. Therein, the difference between the sweet maize/soybean intercropping with crop line ratios of 2:3 (S2B3) and 2:4 (S2B4) were not significant. Furthermore, suitable N input during the sweet maize cultivation in the region were necessary for improving the crop productivity and decreasing the GHGs emission in farmland. Also, the difference of N levels was significant to the GHGs emissions, soil organic carbon sequestration, GHGI and NGHGB. The 300 kg N ha−1 showed the better effect for lowering the NGHGB and CF in sweet maize farmland when keeping crop productivity. The interaction effect of the N level and crop pattern just showed on the crop yields and GHGI. The S2B4 with 300 kg N ha−1 showed significant benefits with respect to maintaining the yields and reducing the net GHGs emissions compared to conventional sweet maize farming system in the Pearl River Delta in China. These advanced agricultural practices contributed to the development of clean agricultural production in China.

Abiotic and biotic factors contribute to CO2 exchange variation at the hourly scale in a semiarid maize cropland

Understanding the variables influencing the carbon budget in agricultural ecosystems is crucial for the prediction of future carbon dynamics. The purpose of this study was to identify the biotic and abiotic determinants of the net ecosystem CO2 exchange (NEE) and net assimilation rate (NPP) in a semiarid maize cropland. The CO2 exchange (NEE and NPP) was measured at different growth stages of maize plants using an improved chamber methodology. Heat map clustering of the correlation coefficients between CO2 exchange and its driving factors demonstrated that soil temperature and air humidity were positively correlated with CO2 emissions regardless of daytime or nighttime, while other factors affecting CO2 exchange were negatively correlated with emissions during daytime yet positively correlated during nighttime. The machine learning algorithm random forest (RF) and structural equation modeling (SEM) were used to analyze the effects of different factors on CO2 exchange. The RF analysis results indicated that for CO2 exchange in the daytime, photosynthetically active radiation (PAR) was the most important variable and presented an importance score of 0.574 for NEE and 0.558 for NPP. The SEM results indicated that in the daytime PAR exerted significant direct and indirect effects on both NEE and NPP, and the standardized direct and indirect effects were −0.668 and 0.022, respectively, for NEE, and the effects were 0.655 and −0.011, respectively for NPP. Like PAR, soil water content also exerted significant direct and indirect effects on both NEE and NPP, but the remaining factors affecting CO2 exchange only have one of the direct or indirect effects, sometimes neither. For CO2 exchange at night, the leaf area was the most important variable and presented an importance score of 0.72 for NEE and 0.45 for NPP. At night, both the direct and indirect effects of most abiotic factors on NEE and NPP were significant.

Increasing temperature shortened the carbon uptake period and decreased the cumulative net ecosystem productivity in a maize cropland in Northeast China

• Carbon uptake period (CUP) was mainly determined by the end date of CUP in autumn. • NEP max explained greater interannual variation in cumulative NEP than CUP. • Both start and end dates of CUP were advanced with increasing winter temperature. • NEP max decreased with increasing precipitation in summer and autumn. • CUP tended to shorten with increasing temperature, thus decreasing cumulative NEP. Phenology—mainly associated with climatic factors—is crucial for the accurate estimation of cumulative annual carbon exchange between terrestrial ecosystems and the atmosphere. However, the effects of changes in phenology on annual vegetation productivity and its regulatory mechanisms remain unclear, particularly in agricultural ecosystems. Therefore, in this study, we examined the associations among cumulative net ecosystem productivity (NEP), phenological metrics, and climatic factors based on long-term (2005–2014) eddy covariance flux and meteorological observations in a maize cropland in Northeast China. The results showed that carbon uptake period (CUP) was mainly determined by the end date of CUP (ECUP) in autumn. Cumulative NEP from May to September (NEP 5−9 ), a period generally corresponding to the growing season, significantly increased with NEP max (defined in this study as the 90th percentile of daily NEP during CUP) and CUP. NEP max explained greater interannual variation in NEP 5−9 than CUP. The start date of CUP (SCUP) and ECUP were both advanced with increasing winter temperature, but ECUP was more temperature-sensitive than SCUP. Thus, CUP tended to shorten with increasing temperature, ultimately decreasing cumulative NEP. In addition, NEP max decreased with increasing precipitation in summer and autumn. The Greenup and MidGreendown dates from the MODIS Global Vegetation Phenology (MCD12Q2) product generally captured the interannual variation in the carbon flux-based SCUP and ECUP, respectively, well. The results of this study would be of great significance for predicting the response of ecosystem productivity to plant phenology shifts in agricultural ecosystems in future climate change scenarios.

A portable rainfall simulator used for sediment and runoff studies with different land treatments

Sediment outflow and soil erosion is concern in worldwide. This study was conducted in the open field on experimental plots using different soil treatments and its effects on sediment outflow and runoff parameters under varying rainfall intensities and land slope conditions. The study involved large number of field experiments for various combinations of urea applications, surface vegetative conditions, land slopes, periods after urea application and rainfall intensities. To create controlled conditions of rainfall, artificial rainfall was generated by developing a portable rainfall simulation system. Five number of experimental plots of 3 m length and 1 m width were constructed and the soil of known properties was filled to create land slopes of 0%, 2%, 4%, 8% and 12% in these five number of experimental plots. As per mandate of this study, apart from control (No crop i.e., bare soil), maize crop land and marigold crop land and the conclusion states that maize crop and marigold crop treatment has an important role in the reduction of runoff and sediment outflow.