Growing Season Of Maize Research Articles

Carbon dioxide fluxes in a farmland ecosystem of the southern Chinese Loess Plateau measured using a chamber-based method.

BackgroundFarmland accounts for a relatively large fraction of the world’s vegetation cover, and the quantification of carbon fluxes over farmland is critical for understanding regional carbon budgets. The carbon cycle of farmland ecosystems has become a focus of global research in the field of carbon dynamics and cycling. The objectives of this study are to monitor the temporal variation in the net ecosystem exchange (NEE) and soil respiration in a spring maize (Zea mays L.) farmland ecosystem of the southern Loess Plateau of China.MethodsA fully automated temperature-controlled flux chamber system was adopted in this study. The system contained nine chambers for CO2 flux measurements, and three treatments were conducted: with and without maize plants in the chamber, as well as a bare field. Observations were conducted from June to September 2011. This time period covers the seedling, jointing, heading, grain filling, and ripening stages of spring maize. Other factors, such as air temperature (Ta), soil temperature (Ts), soil water content (SWC), photosynthetically active radiation (PAR), and precipitation (P), were simultaneously monitored.ResultsThere was observed diurnal variation in the NEE of the maize ecosystem (NEE-maize). A short “noon break” occurred when the PAR intensity was at its maximum, while soil respiration rates had curves with a single peak. During the overall maize growth season, the total NEE-maize was –68.61 g C m−2, and the soil respiration from the maize field (SR-maize) and bare field (SR-bare field) were 245.69 g C m−2 and 114.08 g C m−2, respectively. The temperature sensitivity of soil respiration in the maize field exceeded that in the bare field. Significant negative correlations were found between the NEE, PAR, and temperature (all p-values < 0.01), with both Ta and PAR being the primary factors that affected the CO2 fluxes, collectively contributing 61.7%, 37.2%, and 56.8% to the NEE-maize, SR-maize, and SR-bare field, respectively. It was therefore concluded that both meteorological factors and farming practices have an important impact on the carbon balance process in corn farmland ecosystems. However, it is necessary to conduct long-term observational studies, in order to get a better understanding of the driving mechanism.

Combined application of organic and inorganic fertilizers mitigates ammonia and nitrous oxide emissions in a maize field

This long-term study used a lysimeter platform to monitor the NH3 and N2O emissions of summer maize resulting from various fertilization treatments in the Huanghuaihai area, with the goal to assess the efficiency of fertilization measures aimed at reducing NH3 and N2O losses during the production of summer maize; the results provide a theoretical basis for synergistically improving maize yield and fertilizer utilization efficiency. A 2-year field trial was conducted. The trial included a no-N-fertilizer treatment as a control to study the following three fertilizer treatments: the exclusive application of urea, the exclusive application of cattle manure, and the combined application of organic and inorganic fertilizers. The results show that during the two maize growth seasons included in the trial, the average N2O losses associated with exclusively applying urea, exclusively applying cattle manure, and the combined application of organic and inorganic fertilizers were 273%, 542%, and 376% higher than those associated with the control treatment, respectively. During the same period, the average accumulative ammonia volatilization losses were 311%, 542% and 376% higher than those for the control treatment, respectively. The average nitrogen accumulation resulting from the combined application of organic and inorganic fertilizers was 82% higher than that for the control treatment, 12% higher than that for the exclusive application of cattle manure, and 6% higher than that for the exclusive application of urea. The average grain yield for the combined application of organic and inorganic fertilizers, the exclusive application of urea and the exclusive application of cattle manure were 76%, 68% and 61% higher than that for the control treatment, respectively. Overall, the combined application of organic and inorganic fertilizers showed a lower ammonia volatilization loss than the exclusive application of urea, which resulted in a higher ammonium nitrogen and nitrate nitrogen content in the soil, an increased nitrogen uptake, an increased dry matter accumulation of maize, and a high grain yield and nitrogen recovery efficiency.

Changes in N supply pathways under different long-term fertilization regimes in Northeast China

Different long-term fertilization regimes probably influence N supplying capacity and N cycling processes in soils. However, the effects of fertilization regimes on the pathways of N retention and supply and the impacts of these pathways on crop N uptake remain undocumented. In this study, the contributions of different pathways to N retention and supply were investigated on the basis of a long-term experiment that began in 1990, including six treatments: no fertilizer (CK), recycled manure (M), N and P fertilizers (NP), P and K fertilizers (PK), N, P and K fertilizers (NPK), and NPK fertilizers with recycled manure (NPKM). In the maize growth season, soil microbial mineralization–immobilization turnover (MIT) was the primary driving force of N transformation under treatments without synthetic N. Conversely, NH4+ fixation and release by soil clay minerals prominently regulate N retention and supply under treatments with synthetic N. In general, soil microbial biomass N (SMBN) mineralization and fixed NH4+ release accounted for 51 % of the variation in crop N uptake and the contribution of the latter to crop N uptake was 2-fold greater than that of the former. The synchrony between crop N uptake and fixed NH4+release was higher than that between crop N uptake and SMBN mineralization. Therefore, the fixed NH4+ pool was important in synthetic N regulation at a short or medium temporal scale, especially for soils with high 2:1 clay mineral content. By contrast, MIT dominated N cycling at a long temporal scale. Clarification of the pathways of N retention and supply can provide helpful implications for optimizing N fertilizer management and enhancing the synchrony between crop N demand and soil N supply.

Increasing nitrogen accumulation and reducing nitrogen loss with N-efficient maize cultivars

ABSTRACT Many nitrogen-efficient (N-efficient) maize cultivars have been bred to meet increased food demand and allay urgent environmental concerns, but the effects of these cultivars on increasing N accumulation and reducing N loss in the maize system have not been reported. A two-year field pot experiment was conducted in Southwest China to evaluate the advantages of an N-efficient maize cultivar on N accumulation and N loss in 2014 and 2015. The results showed that the N-efficient maize cultivar ZH 311 had higher N uptake and accumulation ability than the N-inefficient maize cultivar XY 508, especially in the middle and late growth stages. ZH 311 maintained higher residual soil inorganic N in the appropriate growth stage, promoting soil N supply capability and enhancing N uptake while decreasing residual soil inorganic N at harvest and reducing the risk of N leaching. Higher nitrogen accumulation and residual soil inorganic N contributed to lower apparent N loss and apparent N loss efficiency for the N-efficient cultivar than for the N-inefficient cultivar. Moreover, N loss during the maize growth season mainly occurred before silking, and the N-efficient maize cultivar could effectively reduce N loss before silking because of its earlier N uptake ability. Overall, the selection of N-efficient maize cultivars is not only an important measure to enhance N use efficiency but also an important means to reduce the loss of N and environmental pollution, especially at low and medium N levels.

Changes in soil organic carbon fractions and bacterial community composition under different tillage and organic fertiliser application in a maize−wheat rotation system

ABSTRACT The objective of this study was to assess the impact of different tillage and organic fertiliser regimes on soil carbon fractions and bacterial community composition within a maize–wheat cropping system. We conducted a six-year experiment on the Huang-Huai-Hai Plain of China. Six treatments were established: deep tillage (DT), shallow tillage (ST), no-tillage (NT), deep tillage with organic fertiliser (DTF), shallow tillage with organic fertiliser (STF), and no-tillage with organic fertiliser (NTF). Results indicated that during the winter wheat growing season, the highest contents of soil organic carbon (SOC) and easily-oxidised organic carbon (EOC) were in the STF treatment. During the summer maizegrowing season, the DTF treatment had the highest SOC and EOC contents. Compared with the other treatments, the NTF treatment had higher Chao1 and Shannon indices for bacteria; however, the relative abundance of Proteobacteria is highest in all treatments. A redundancy analysis (RDA) revealed that bacterial community composition was correlated with variation of the SOC, DOC, EOC, and microbial biomass carbon (MBC). Our results showed that combining the two components of the SOC fractions and bacterial community composition, STF practice in a maize–wheat rotation was a sustainable approach to optimising soil structure and improving soil quality.

Irrigation scheduling of maize based on plant and soil indices with surface drip irrigation subjected to different irrigation regimes

A study was conducted on a research farm at Urmia University under drip irrigation in order to schedule the irrigation of maize based on plant indices: crop water stress index (CWSI) and relative water content (RWC) and soil indices: soil water (SW) and soil penetration resistance (Q) in climatic conditions of Urmia region in Iran. This study was conducted in the form of randomized complete block design with four irrigation levels including two levels of deficit irrigation (I1) (Crop water requirement (CWR) of 0.5) and I2 (0.75CWR), a full-irrigation level of I3 (1.0CWR) and an over-irrigation level of I4 (1.25CWR) with three replications. I4 treatment for air-filled porosity was considered in the soil. For irrigation scheduling, lower and upper baseline and CWSI equations for I1, I2 and I3 treatments were calculated during plant growth period. Using the extracted baselines, the mean CWSI values during maize growth season for I1, I2 and I3 treatments were calculated to be 0.53, 0.44 and 0.28 respectively. The threshold limit of water stress index of I3 treatment was the basis of irrigation scheduling. Then, relationships were provided for determining the irrigation time using CWSI in Urmia climate for three maize growth stages. In addition, among soil and plant indices which were simultaneously measured at maximum stress hour were used as a complementary indicator to eliminate CWSI constraints. Using the regression relationships extracted between the indices, the water status of plant can be determined by only measuring the canopy temperature (Tc) without measuring the RWC, SW and Q. It should be noted that in the region of Urmia, the critical values of the difference between the Tc and the air temperature, Q and SW for maize were respectively 1.5 °C, 3.6 MPa and 0.27 cm3 cm−3 (matric potential of 8900 hPa).

Characterization of runoff and sediment associated with rill erosion in sloping farmland during the maize-growing season based on rescaled range and wavelet analyses

Rill erosion is one of the most serious problems in sloping farmland of purple soil. The formation and evolution of runoff and sediment associated with rill erosion are complex processes that are influenced by many factors. The aim of the present study was to investigate the temporal variation characteristics of runoff and sediment associated with rill erosion during the maize-growing season. Simulated rainfall experiments (1.0, 1.5 and 2.0 mm min−1) were carried out in three experimental croplands on a typical slope gradient of 15°. Multi-scale temporal variation characteristics of runoff and sediment associated with rill erosion were identified by rescaled range (R/S) and wavelet analyses. The results showed that the Hurst index of the runoff ranged between 0.572 and 0.875 during the maize-growing season, while those of the sediment ranged between 0.575 and 0.855, indicating a long-range positive correlation. Therefore, the time series of runoff and sediment were persistent time series, and the future trends of runoff and sediment would be consistent with the present. The principal cycles of runoff and sediment presented an initial increasing and then a decreasing trend with maize growth, and the runoff and sediment yield varied periodically every 8–15 minutes. The changes in the primary cycles of runoff and sediment were basically consistent with the changes in vegetation coverage. The results provided a new insight for describing multi-time scale characteristics of runoff and sediment associated with rill erosion.

Soil water use and crop yield increase under different long-term fertilization practices incorporated with two-year tillage rotations

Water shortage and soil nutritionally depleted are the most limiting factors of crop production on the Loess Plateau. Conservation tillage rotation, conserved soil water and enhanced soil fertility effectively, produced high and stable crop yields in a spring maize-winter wheat-fallow rotation over a two-year period (hereafter called maize-wheat-fallow rotation). Corresponding and appropriate fertilization practices should enable the full potential of tillage rotation. Therefore, a long-term two-factor split-plot experiment (2007–2016) was established in Heyang County, Shaanxi Province, China, a typical rainfed dryland agricultural region. Beginning in 2007, three fertilization practices (balanced fertilization (BF), low fertilization (LF) and conventional fertilization (CF)) and four tillage systems (no tillage rotated with subsoiling annually (NS), subsoiling rotated with conventional tillage annually (SC), conventional tillage rotated with no tillage annually (CN), and continuous conventional tillage (CT)) were conducted to assess crop yield and soil water variation. The results showed that CCN (CF + CN, 5440 kg ha−1) and BNS (BF+NS, 8415 kg ha −1) produced the highest crop yield for winter wheat and spring maize, respectively. LNS (LF + NS, 419 mm) had a better soil water condition in fallow periods. NS and CN rotations had a better soil water condition (reserved more soil water for crop growth) than SC and CT during the wheat and maize growth season. However, both the average ET of winter wheat and spring maize under all of the treatments had no significant differences (P > 0.05) in ten years. In ten years, NS and CN rotations had higher water use efficiency (WUEs) than the SC rotation and CT, BNS had the highest WUE (19.0 kg ha −1 mm−1) for the spring maize – winter wheat rotation. Tillage rotation and fertilization had an interactive effect on soil water use and crop growth, and the results might clarify the response of crop yield and soil water variation to fertilization and tillage rotations. For further and sustainable development of crop production, BNS (5133 and 8415 kg ha −1 for wheat and maize yield, respectively; soil water in fallow: 386 mm) and BCN (5221 and 8116 kg ha −1 for wheat and maize yield, respectively; soil water in fallow: 388 mm) are recommended as the optimal fertilization and tillage rotations for rainfed crop production on the Loess Plateau.

Effects of continuous plastic mulching on crop growth in a winter wheat-summer maize rotation system on the Loess Plateau of China

The use of plastic mulching is considered to be a primary solution to improve crop productivity in dryland farming of northwest China. However, the interaction of this management practice on cereal crop growth and environment factors is not clearly understood. Based on a three rotation cycles field experiment from 2013 to 2016, this study, based on the logistic equation, tried to quantify the impacts of continuous plastic mulching (PM) on the crop growth dynamics in a winter wheat (Triticum aestivum L.) and summer maize (Zea mays L.) rotation system on the Loess Plateau, northwest China. The results showed that the logistic equation did well in the characterization of wheat and maize growth dynamics with its characteristic parameter (e.g., inflection points). Both in wheat and maize growth seasons, the plant height accumulation occurred earlier than the aboveground biomass accumulation. In comparison to the crop growth under the non-mulched treatment, the acceleration effects of PM treatment on the crop growth continued to be enhanced when the apical meristem was underground. For wheat, the improved soil hydrothermal conditions under the PM treatment effectively accelerated the wheat leaves’ appearance and the tiller nodes development, which increased the final spike number and grain yields. For maize, because of the greater radiation and water use efficiency during the maize growth seasons, the PM treatment increased the maize kernels per spike and the thousand-seed weight, and significantly improved maize yields. Attributable to improved soil hydrothermal conditions and beneficial interactions between the crop growth and the external environment, the PM treatment significantly improved crop production and increased resource use efficiency, which may greatly contribute to the sustainability of local dryland farming.

Drought indices based on MODIS data compared over a maize-growing season in Songliao Plain, China

Many indices based on MODIS data are used to monitor the process of agricultural drought, such as apparent thermal inertia (ATI) and temperature vegetation dryness index (TVDI). Notable differences in performance and geographic predictions exist among these indices. We statistically evaluated the performance of different drought indices for a known drought process in 2014 in the typical rainfed maize region of Songliao Plain, China, using a linear regression model based on the relationships between indices and soil moisture data. Our results show that during the growth season of May to September, the indices performed independently with changing curves, particularly in different phenological periods. By contrast, correlations tended to be higher for ATI than for other indices in the early vegetative growth stage, whereas small differences were detected among the other indices in the late vegetative to late reproductive growth stages. Our results confirm that the TVDI can be the best choice to detect agricultural drought in the study area.

The effects of rotating conservation tillage with conventional tillage on soil properties and grain yields in winter wheat-spring maize rotations

Intensive tillage in conventional tillage systems reinforces water stress effects on crop growth, limiting yields from dryland agriculture. Conservation tillage can reduce soil evaporation and conserve more soil water in fields, but long-term, mono-conservation tillage may lead to low crop yields. The rotation of conventional tillage with conservation tillage may offset some of the defects generated by the mono-tillage practices of either conventional or conservation tillage, improve crop yields and provide better soil conditions. A long-term tillage rotation experiment (2007–2016) was established to assess the effects of rotating conservation tillage with conventional tillage on soil water and crop productivity in a winter wheat-spring maize rotation field in Heyang County, Shaanxi Province, a typical semi-arid region of the Loess Plateau, China. Four tillage treatments were applied over ten years, as follows: ST/CT (subsoiling was performed during the first year then rotated with conventional tillage in the second year), CT/NT (conventional tillage during the first year and then rotated with no-tillage in the second year), NT (no tillage applied in any year) and CT (conventional tillage applied annually). Compared with CT and NT, the CT/NT rotation significantly decreased the soil bulk density and increased the soil porosity in the 0–60 cm soil layer after ten years (P < 0.05). The CT/NT and ST/CT rotations increased the minimum soil temperature during the wheat growth season and decreased the maximum soil temperature during the maize growth season. In fallow periods, the mean soil water storage and soil water content values for the CT/NT rotation were 8.7% and 4.8–10.1% higher than those of the CT treatment, respectively. The CT/NT rotation consumed more soil water during the winter wheat growth season and less soil water during the spring maize growth season compared to the NT and CT treatments. Over ten years, the ST/CT rotation produced higher crop yields (winter wheat: 5231 kg ha−1, spring maize: 8388 kg ha−1), while the CT/NT rotation had a higher WUE (winter wheat: 15.5 kg ha−1 mm−1, ST/CT: 20.6 kg ha−1 mm−1) than either NT or CT alone. The CT/NT rotation also had an increased straw yield (mean value: 9952 kg ha−1) and economic profit (6776 yuan ha−1). Moreover, the CT/NT and ST/CT rotations provided an optimal SOC distribution in the 0–60 cm soil layer. With respect to comprehensive productivity, the CT/NT rotation provided relatively better soil conditions and crop yields during the winter wheat-spring maize rotations. We recommend using the CT/NT rotation as the optimal tillage system for the sustainable production of crops under conditions of semi-arid agricultural production in the Loess Plateau of China.

Climate zones determine where substantial increases of maize yields can be attained in Northeast China

As the growth in global population has led to greater demands for food and energy, societies have been pressured to increase food production. Closing the gap between current and potential yields is one means of producing more food. In this study, we first identify the gaps between the potential yield and actual on-farm yield of maize for ten climate zones (CZs) in Northeast China (NEC) from 1961 to 2010. We then use trend analysis to assess yield gaps caused by suboptimal water availability (YGw). Finally, we identify the CZs where maize yields could be increased through improved irrigation management. Nonparametric trend analysis showed an estimated regional area-averaged yield gap of 64% between potential yield and actual on-farm yield; this gap decreased by 11.0% per decade over the study period (p < 0.01). Although yield gaps have fallen to 43% during the past decade, on-farm maize yield still accounts for only 57% of potential yield. Therefore, there is still a considerable yield gap in maize production in NEC. Simulation results indicated that the average YGw of 23% in NEC is due to suboptimal water availability. Moreover, in CZs with a positive water deficit, the YGw ranged from 14 to 48%; in the remaining CZs, the YGw ranged from 5 to 13%. We conclude that there are substantial opportunities to increase maize production by up to 2.8 t ha−1 through improved irrigation management in cases where the limited irrigation resources can be improved, especially in CZs that receive less than 450 mm of precipitation during the maize-growing season.

Crop yield and soil properties of dryland winter wheat-spring maize rotation in response to 10-year fertilization and conservation tillage practices on the Loess Plateau

Drought and nutrient deficiency are the principal factors limiting crop production in arid and semi-arid areas. Conservation tillage can maintain and increase grain yields by enhancing soil fertility and conserving more soil water in the field. However, farmers without access to mineral fertilizers cannot compensate for the soil nutrient deficiencies for crop production, and the crops will suffer yield reductions. Site-specific fertilizer application with conservation tillage practice management is the key to achieving a high and sustainable crop yield. A long-term (2007–2016) two-factor, spilt-plot experiment was established to assess the effects of fertilization {balanced fertilization (BF), low fertilization (LF), conventional fertilization (CF)} and conservation tillage practices {no tillage (NT), subsoiling (ST), conventional tillage (CT)} on grain yield, soil water and soil nutrients. The aim of this experiment was to select an optimal fertilization and tillage management system for crop production in the Loess Plateau, a typical semi-arid and rainfed area of China. Ten-year data showed that subsoiling with balanced fertilization (BST) increased the grain (6465 kg ha−1) and straw yield (9792 kg ha−1), but no tillage with balanced fertilization (BNT) was observed to provide the highest economic profit for farmers (6416 yuan ha-1). No tillage with low fertilization (LNT) was the optimal management for soil water conservation in fields that could preserve more soil water in fallow land (mean value: 425 mm) and provide more soil water during the wheat (mean value: 387 mm) and maize (mean value: 420 mm) growth season. The LNT consumed less soil water in the crop growth season (mean value: 105.4 mm), but the BST (18.5 kg ha−1 mm−1) showed a higher water use efficiency (WUE). The BF and NT showed better soil nutrient conditions (soil organic matter(SOM), available N, P and K) over the ten years and provided better soil water and balanced soil nutrient conditions for crop growth. The BNT and BST were recommended as the optimal and economic fertilization with tillage management systems for maintaining high grain yields by using soil water efficiently and enhancing soil fertility in a winter wheat-spring maize rotation on the Loess Plateau.

The impact of non-isothermal soil moisture transport on evaporation fluxes in a maize cropland

The process of evaporation interacts with the soil, which has various comprehensive mechanisms. Multiphase flow models solve air, vapour, water, and heat transport equations to simulate non-isothermal soil moisture transport of both liquid water and vapor flow, but are only applied in non-vegetated soils. For (sparsely) vegetated soils often energy balance models are used, however these lack the detailed information on non-isothermal soil moisture transport. In this study we coupled a multiphase flow model with a two-layer energy balance model to study the impact of non-isothermal soil moisture transport on evaporation fluxes (i.e., interception, transpiration, and soil evaporation) for vegetated soils. The proposed model was implemented at an experimental agricultural site in Florida, US, covering an entire maize-growing season (67 days). As the crops grew, transpiration and interception became gradually dominated, while the fraction of soil evaporation dropped from 100% to less than 20%. The mechanisms of soil evaporation vary depending on the soil moisture content. After precipitation the soil moisture content increased, exfiltration of the liquid water flow could transport sufficient water to sustain evaporation from soil, and the soil vapor transport was not significant. However, after a sufficient dry-down period, the soil moisture content significantly reduced, and the soil vapour flow significantly contributed to the upward moisture transport in topmost soil. A sensitivity analysis found that the simulations of moisture content and temperature at the soil surface varied substantially when including the advective (i.e., advection and mechanical dispersion) vapour transport in simulation, including the mechanism of advective vapour transport decreased soil evaporation rate under wet condition, while vice versa under dry condition. The results showed that the formulation of advective soil vapor transport in a soil-vegetation-atmosphere transfer continuum can affect the simulated evaporation fluxes, especially under dry condition.

Assessment of short- and long-term memory in trends of major climatic variables over Iran: 1966–2015

In arid and semi-arid regions, water scarcity is the crucial issue for crop production. Identifying the spatial and temporal trends in aridity, especially during the crop-growing season, is important for farmers to manage their agricultural practices. This will become especially relevant when considering climate change projections. To reliably determine the actual trends, the influence of short- and long-term memory should be removed from the trend analysis. The objective of this study is to investigate the effect of short- and long-term memory on estimates of trends in two aridity indicators—the inverted De Martonne (ϕIDM) and Budyko (ϕB) indices. The analysis is done using precipitation and temperature data over Iran for a 50-year period (1966–2015) at three temporal scales: annual, wheat-growing season (October–June), and maize-growing season (May–November). For this purpose, the original and the modified Mann–Kendall tests (i.e., modified by three methods of trend free pre-whitening (TFPT), effective sample size (ESS), and long-term persistence (LTP)) are used to investigate the temporal trends in aridity indices, precipitation, and temperature by taking into account the effect of short- and long-term memory. Precipitation and temperature data were provided by the Islamic Republic of Iran Meteorological Organization (IRIMO). The temporal trend analysis showed that aridity increased from 1966 to 2015 at the annual and wheat-growing season scales, which is due to a decreasing trend in precipitation and an increasing trend in mean temperature at these two timescales. The trend in aridity indices was decreasing in the maize-growing season, since precipitation has an increasing trend for most parts of Iran in that season. The increasing trend in aridity indices is significant in Western Iran, which can be related to the significantly more negative trend in precipitation in the West. This increasing trend in aridity could result in an increasing crop water requirement and a significant reduction in the crop production and water use efficiency. Furthermore, the modified Mann–Kendall tests indicated that unlike temperature series, precipitation, ϕIDM, and ϕB series are not affected by short- and long-term memory. Our results can help decision makers and water resource managers to adopt appropriate policy strategies for sustainable development in the field of irrigated agriculture and water resources management.

Diversity of Leafhoppers (Hemiptera: Cicadellidae) Associated with Border Grasses and Maize During the Wet and Dry Seasons in Mexico.

Leafhoppers constitute one of the largest groups of pests causing damage to crops worldwide. Edge grasses, which are border crops (also known as border grasses), contain diverse plant species and maintain large populations of leafhoppers during the tropical dry and wet seasons. However, little is known about the diversity of leafhoppers on these grasses. The objective of this study was to characterize the diversity of leafhoppers on maize and on surrounding border grasses during the dry and wet seasons. Leafhopper adults were collected with a sweep net from border grasses during the dry season, when maize is absent. During the wet, maize-growing season, leafhoppers were collected in both the maize fields and their surrounding edge grasses. A highly diverse (H' = 1.97 ± 2.03) leafhopper population was seen on the edge grasses during the dry season, and during the wet season, leafhopper diversity was higher in the edge grasses (H'= 1.79 ± 1.72) than in the maize fields themselves (H'= 1.67 ± 1.12). Throughout the wet season, the most abundant leafhopper species in border grasses were Stirellus bicolor (Van Duzee) (Hemiptera: Cicadellidae), Graminella sonora (Ball) (Hemiptera: Cicadellidae), and Balclutha incisa (Matsumura) (Hemiptera: Cicadellidae), whereas Dalbulus maidis (DeLong) (Hemiptera: Cicadellidae) was the most abundant species in maize fields. All of these species were from the subfamily Deltocephalinae. Canonical Component Analysis showed that leafhopper abundance of Sibovia compta (Fowler) (Hemiptera: Cicadellidae), Graphocephala aurolineata (Fowler) (Hemiptera: Cicadellidae), D. maidis, and S. bicolor was associated with abiotic factors such as relative humidity, soil moisture, temperature, and pluvial precipitation. Nevertheless, for most leafhopper species, abundances were not significantly correlated with the abiotic variables measured.

Non-linear trends and fluctuations in temperature during different growth stages of summer maize in the North China Plain from 1960 to 2014

North China Plain has undergone severe warming trends since the 1950s, but whether this trend is the same during different growth phases for crops remains unknown. Thus, we analyzed the non-linear changes in the minimum temperature (Tmin), mean temperature (Tmean) and maximum temperature (Tmax) using the Ensemble Empirical Mode Decomposition method during each growth stage of summer maize based on daily temperature data from 1960 to 2014. Our results strongly suggest that the trends and fluctuations in temperature change are non-linear. These changes can be categorized into four types of trend change according to the combinations of decreasing and increasing trends, and 8 fluctuation modes dominated by the fluctuations of expansion and shrinkage. The amplitude of the fluctuation is primarily expansion in the sowing–jointing stage and shrinkage in the jointing–maturity stage. Moreover, the temperature changes are inconsistent within each growth stage and are not consistent with the overall warming trend observed over the last 55 years. A transition period occurred in both the 1980s and the 1990s for temperatures during the sowing–tasseling stage. Furthermore, the cooling trend of the Tmax was significant in the sowing–emergence stage, while this cooling trend was not obvious for both Tmean and Tmin in the jointing–tasseling stage. These results showed that temperature change was significantly different in different stages of the maize growth season. The results can serve as a scientific basis for a better understanding of the actual changes in the regional surface air temperature and agronomic heat resources.

Characteristics of Biochar-mediated N2O Emissions from Soils of Different Surface Conditions

It was aimed to investigate the response to biochar addition on N2O gas production and emission in different surface conditions. To study the dynamic changes of soil N2O release, soil nitrate(NO3--N) and ammonium(NH4+-N), a field trials experiment was conducted from 2014 to 2015 in wheat and corn season, which contained three treatments[the blank control group (CK), biochar applied at 5 t·(hm2·a)-1(BC5) and 45 t·(hm2·a)-1(BC45), respectively] under crop cultivation(+) and non-cultivation(-) condition. The results indicated that:1 During the season of wheat growth, the soil N2O emissions of CK+, BC5+, BC45+ were 21.70-88.91, 21.42-130.09, 64.44-179.58 μg·(m2·h)-1 respectively, and that of BC45+ possessed a higher value than those of the other treatments(P<0.05). Compared with wheat winter period, the soil N2O emissions of the three treatments decreased evidently in wheat peak stage(returning green and jointing stage, booting and heading stage) (P<0.05), and the amplification of BC45+ reduced by 18.43% and 14.62% in comparison with CK+ and BC5+ in wheat booting and heading stages. In the early stage of maize growth, the soil N2O emissions of BC45+ were significantly increased compared with CK+ and BC5+(P<0.05). However, there were no significant differences among treatments of maize heading stage and mature stage. It showed that the biochar-mediated promotion effect of soil N2O emissions was effectively inhibited by crop growth and the increase of surface mulch. Besides, the result of soil N2O release in the same treatment had also confirmed this conclusion in bare land. 2 Under the conditions of wheat cultivation and homochronous non-cultivation, the soil NO3--N and NH4+-N contents of BC5+ and BC45+ treatments were raised with respect to CK+, but the values dropped significantly in wheat peak stage, especially for BC45+ treatment, with 96.44% and 69.40% decrease respectively. The soil inorganic nitrogen content of maize growth season had a similar trend in wheat season. Parallel to this result of the apparently falling soil NO3--N and NH4+-N concentrations, the soil N2O emissions of BC45+ also declined remarkably in peak stage. The decline in respiratory substrate caused by the increase of nitrogen uptake by crop growth, may be one of the reasons for the decrease of N2O emission. 3 In wheat growth season, the soil pH values of the biochar treatments were improved from 4.62 to 5.18. In maize season, the soil pH values ranged from 4.42 to 5.02. When the soil pH value was relatively low, the soil N2O emission was high, and vice versa. The soil N2O emission was partly influenced by the soil pH value.

THE RATIO OF CO2–C EMISSION TO GRAIN YIELD IN SUMMER MAIZE CULTIVATED UNDER DIFFERENT SOIL TILLAGE AND STRAW APPLICATION CONDITIONS

SUMMARYThe relationship between climate, crop growth and crop yield is complicated. This study aimed to determine the ratio of CO2–C emission to grain yield, the field treatments were initiated in 2003, but the measurements for this analysis were collected during the summer maize-growing seasons of 2011 and 2012 in the North China Plain. The experiment showed that conventional tillage with straw application significantly increased grain yield and the ratio of CO2–C emission to grain yield of summer maize. The mean soil CO2–C emission rate with no tillage was significantly lower than that when conventional tillage was used; however, straw application significantly increased the soil CO2–C emission rate, irrespective of whether tillage was performed or not. This was mainly because straw application changed the soil total porosity and organic carbon content. In conclusion, the results of this study support the hypothesis that the ratio of CO2–C emission to grain yield in the North China Plain can be increased by straw application, whereas no tillage decreases this ratio.

Effects of plastic film mulching on soil greenhouse gases (CO2, CH4 and N2O) concentration within soil profiles in maize fields on the Loess Plateau, China

AbstractTo better understand the effects of plastic film mulching on soil greenhouse gases (GHGs) emissions, we compared seasonal and vertical variations of GHG concentrations at seven soil depths in maize (Zea mays L.) fields at Changwu station in Shaanxi, a semi-humid region, between 2012 and 2013. Gas samples were taken simultaneously every one week from non-mulched (BP) and plastic film-mulched (FM) field plots. The results showed that the concentration of GHGs varied distinctly at the soil-atmosphere interface and in the soil profile during the maize growing season (MS). Both carbon dioxide (CO2) and nitrous oxide (N2O) concentrations increased with increasement of soil depth, while the methane (CH4) concentrations decreased with increasement of soil depth. A strong seasonal variation pattern was found for CO2 and N2O concentrations, as compared to an inconspicuous seasonal variation of CH4 concentrations. The mean CO2 and N2O concentrations were higher, but the mean CH4 concentration in the soil profiles was lower in the FM plots than in the BP plots. The results of this study suggested that plastic film mulching significantly increased the potential emissions of CO2 and N2O from the soil, and promoted CH4 absorption by the soil, particularly during the MS.