Maize Cropping System Research Articles

Effects of plastic mulch and nitrogen fertilizer on the soil microbial community, enzymatic activity and yield performance in a dryland maize cropping system

AbstractFarming practices that integrate plastic film mulching and nitrogen (N) fertilization have been extensively used to enhance crop productivity. However, the interactive effects of mulching and N application on soil microbial properties and crop yields have received little attention. A 2‐year field experiment was carried out in the Loess Plateau to investigate the independent and combined effects of plastic mulch and N application rate on the soil microbial population, enzymatic activity and grain yield. From 2016 to 2017, two mulching patterns (i.e., plastic mulching and no mulching) were exposed to five different N application rates (0 (N0), 80 (N80), 160 (N160), 200 (N200) and 240 (N240) kg N ha−1). N application significantly affected the soil microbial community composition, as suggested by significant increases in soil total bacteria, cellulose‐decomposing bacteria and the bacterial‐to‐fungal ratio with N rates. In contrast, the mulching pattern significantly affected soil extracellular enzyme production. Furthermore, there were significant effects of mulching, N application and their interaction on grain yield. The highest grain yield (11,728 kg N ha−1 in 2016 and 12,350 kg N ha−1 in 2017) in both growing seasons was consistently obtained under plastic mulching with a N level of 200 kg N ha−1. Our study showed that plastic mulching significantly affected extracellular enzyme production, and N fertilizer application significantly affected the composition of the soil microbial community.Highlights Independent and coupled effects of mulching and N application on soil biological properties and grain performance were explored. N application significantly influenced soil microbial community composition. Mulching pattern rather than N application independently and significantly affected soil extracellular enzyme production The combined application of plastic mulching with 200 kg N ha−1 should be seem as an optimum crop production pattern in this area.

Effect of conservation agriculture and residue management on yield and economics of cotton – maize cropping system

Effect of conservation agriculture and residue management on yield and economics of cotton – maize cropping system

Spatiotemporal variations in soil CO2 fluxes under a winter wheat-summer maize cropping system in the North China Plain

Most studies on soil CO2 fluxes focus on the upper soil layers (i.e., 0–200 mm); however, there is a lack of investigation into soil layers below 200 mm, even though about half of soil organic carbon (SOC) is stored at these depths. In order to investigate the responses of CO2 fluxes in subsurface soils to crop residue incorporation in the topsoil, a field experiment comprising two treatments (i.e., conventional tillage with and without crop residue incorporation) was carried out under a winter wheat-summer maize cropping system from 2014 to 2016 in the Yucheng Agricultural Station, Shandong Province, China. The results showed that soil CO2 fluxes had large spatiotemporal variabilities and were significantly affected by crop residue applications (P < 0.05). Soil CO2 fluxes increased with soil depth. The CO2 fluxes from 100 to 400 mm soil depths were 1.1–5.1 times higher than those from 0 to 100 mm soil depths. Incorporation of crop residues into the soil significantly increased soil CO2 fluxes in all sampled layers (P < 0.05), and the magnitude increased with increasing soil depth. Soil moisture and the ratio of soil dissolved organic carbon to nitrogen (DOC/DON) were the dominant factors regulating soil CO2 fluxes in the wheat growing season, whereas soil DON concentrations dominated in the maize growing season. Our study indicated that deep soil C was more vulnerable to the incorporation of crop residues than the C present in surface soil. Incorporation of crop residues into surface soil might not increase SOC sequestration in the subsurface soil.

Maize Intercropping Systems Improve Nutrient for the Cowpea Crop in Sandy Soils

ABSTRACTSandy soils are characterized by their low fertility and low ability to supply nutrients to plants. However, the adoption of agronomic practices, such as the use of intercropping systems, can promote nutrient cycling and improve the production potential of sandy soils. A study was conducted to evaluate the nutrient accumulation and cycling of six maize cropping systems (maize alone and intercropped with cover crops), and to evaluate the nutrition and yield of cowpea crop in the no-till system (NT), grown in succession to maize intercropping systems. The treatments consisted of growing maize alone (monoculture), and five maize intercropping systems: maize + palisade grass (Urochloa brizantha); maize + sunn hemp (Crotalaria juncea); maize + pigeon pea (Cajanus cajan); maize + palisade grass + sunn hemp; and maize + p-alisade grass + pigeon pea. In the 2016/2017 growing season, dry matter (DM) production, macronutrient accumulation and exportation in maize grains were evaluated. In the 2017/2018 season, DM accumulation, leaf nutrient concentration and grain yield of cowpea crop were measured. Intercropping with cover crops influences maize grain yield, macronutrient contents, and straw dry matter accumulation. The grain yield of cowpea was higher than 600 kg ha–1, due to the benefits of cropping under the crop residues of maize intercropped with cover crops.

Nitrogen Rate and Hybrid Selection Matters Productivity of Maize–Maize Cropping System under Irrigated Arid Environment of Southern Punjab, Pakistan

Maize is sown during spring and autumn seasons in Pakistan; however, studies on inter-seasonal variability on maize productivity, agronomic and nitrogen use efficiencies (NUEs) are limited. Therefore optimization of nitrogen (N) rate and hybrids selection for each season is critical to harvest better yield in maize–maize cropping system. Two independent field experiments were conducted to optimize N rates for different hybrids to improve maize productivity and NUEs in spring and autumn seasons during 2016 and 2017. During spring season, three spring-hybrids (P-33M15, M-DK6525 and S-NK8441) and during autumn season, three autumn-hybrids (P-30R50, M-DK6714 and S-NK6621) were sown under five N levels i.e., 0, 80, 160, 240 and 320 kg ha−1. Maize yield and related traits, and NUEs were improved with each higher level of N application. Highest and lowest grain yield, agronomic and economic NUEs were recorded at 320 kg N ha−1 and without N application, respectively in both seasons. Likewise, highest grain yield and NUEs were observed by spring-hybrid P-33M15 and autumn-hybrid P-30R50, while lowest were obtained by spring hybrid S-NK8441 and autumn hybrid S-NK6621 during both years. Nonetheless, maximum net income and benefit: cost ratio was observed by spring-hybrid P-33M15 and autumn-hybrid P-30R50 at higher N level (320 kg ha−1) and maize cultivation without N was not profitable in both seasons. Maize cultivation with N application at 320 kg ha−1 seemed a viable option to get maximum productivity, economic returns and NUEs of maize–maize cropping system in irrigated arid environment of southern Punjab, Pakistan and might be for other areas having similar environmental conditions.

Wheat‐derived soil organic carbon accumulates more than its maize counterpart in a wheat–maize cropping system after 21 years

AbstractFertilization is the most common way to supply nutrients to the soil and to maintain crop productivity in agricultural ecosystems, which may also influence soil organic carbon (SOC) accumulation rates. In 1996, we set up a long‐term field experiment to explore the effect of fertilization on soil properties in a winter wheat–summer maize cropping system in the North China Plain. Eight treatments included: no fertilization (Ct), nitrogen (N), phosphorus (P) and N combined with P (NP) fertilizer application with or without potassium (K). After 21 years of fertilization, N application did not increase soil total N content, but P application significantly increased soil total P contents by 33.9%. The single application of N or P did not significantly affect SOC content, whereas the NP combination significantly increased SOC contents by 22.1 and 29.6% compared to Ct in the no K and K treatments, respectively. The natural 13C abundance approach and the SOC contents suggested that the NP combination increased C3 wheat‐derived SOC by 37.5 and 49.8% in the no K and K treatments, respectively. However, fertilization had no impact on C4 maize‐derived SOC content. Wheat‐derived SOC was positively correlated with the wheat yield, whereas maize‐derived SOC was not correlated with the maize yield, which indicated that wheat‐derived SOC accumulated more than maize‐derived SOC in the wheat–maize cropping system. In addition, soil inorganic carbon (SIC) and its compositions were not affected by the long‐term fertilization. Our results indicate that N combined with P application is more beneficial than N or P alone to enlarge SOC sequestration in the North China Plain, especially for wheat‐derived SOC. Thus, in soil with nutrient limitations, nutrient resources should be supplied with priority to the wheat growing season in wheat–maize cropping systems, to maintain or enlarge SOC storage.Highlights Long‐term N combined with P application increased wheat‐derived SOC Wheat‐derived SOC accumulated more than maize‐derived SOC in the cropping system Wheat yield was lower than maize in the wheat–maize cropping system Long‐term N, P or NP fertilization did not influence soil inorganic carbon

Effects of Genetically Modified (GM) Maize Adoption in Small Scale Farms on Cropping Systems of the Eastern Cape Province, South Africa

Genetically modified (GM) crops are being promoted to ensure agricultural productivity and food security to keep pace with the ever-growing global population and food demand. In as much as agricultural technological advancements are crucial, there is need to strike a balance with agrobiodiversity for sustainable farming. Surveys were conducted in five municipal districts of the Eastern Cape Province to determine GM-technology adoption effects on maize cropping systems, agronomic practices and farmers’ perceptions of production constraints. Interviews of 232 farmers, independent (IF) 22.4% and government sponsored (GCP) 77.6%, revealed a wide variation in agronomic practices amongst them. Results indicate significant differences on the maize cropping systems practiced by the Eastern Cape small scale farmers. The majority (81.7%) of interviewed small scale GCP farmers produce maize as a monocrop, under dryland (91.7%) through conventional tillage practices (100%). In contrast, IF farmers practiced maize sole cropping (34.6%), under dryland (90.4%) through conventional tillage practices (86.5%). There were significant differences between the two farmers’ groups on crop mixture used (p=0.00), crop rotations (p=0.02), choice of maize varieties (p=0.00) and fertiliser use (p=0.00). Demographic and farm characteristics, type of land cultivation, production constraints, pest problems and pest management practices are discussed. The findings suggest the need to devise a system that will improve compatibility of GM-maize technology and traditional farming practices to ensure sustainable farming and food security for the resource poor farmers. The government support schemes seeking to enhance agricultural productivity need to equip farmers with the necessary versatile farming skills.

The Influence of Conservative Tillage Systems on Physico-Chemical Properties and Yield under a Cambic Chernozem from Northeastern Part of Romania

The long-term experiment was carried out during 2005-2018, with samples collected on the experimental farm of the University of Agricultural Sciences and Veterinary Medicine in the city of Iasi (47º07` N latitude, 27º30` E longitude). The soil under investigation is classified as Cambic Chernozem (WRB) with a clay-loamy texture. Initial physical characteristics of the soil on 0-20 cm depth were: bulk density 1.33 g.cm-3 , pH (1:2.5) 6.23, clay 364.2 g.kg-1 , silt 263.2 g.kg-1 , loam 372.6 g.kg-1 , humus 2.95%. In the last 5 years a continuous maize cropping system was used. The tillage treatments included: (1) No-till: direct drilling in untilled soil with a disc drill without previous removal of residues, using a FABIMAG FG01 seeder (NT); (2) a reduced system using a chisel at 22-25 cm depth, after harvest without overturning the furrow (RT); (3) moldboard ploughing after harvest to a soil depth of 28-30 cm (CT). The crumbled and loosened soil was turned over and thereby residues were fully incorporated into the soil. After the harvest of pre-crop, stubble breaking (disking to the depth 10 cm) was used. Seedbed preparation was applied using a compactor after chisel and conventional tillage. In spring the weeds were suppressed by total herbicides before seeding. Crop-specific fertilization was performed according to good agricultural practice. Combine harvest was performed in October (between 5th and 28th) using a Wintersteiger Delta Plot Combine. Tillage systems affected soil penetration resistance (PR) under maize crop only for certain soil depths. At 0-5 cm depth, the highest value (0.78 MPa) was recorded on no-till system, whilst in the case of the other two variants the values ranged from 0.56 to 0.61 MPa. In CT variant at 30-40 cm, we noticed a compacted layer (2.54 MPa) indicating the existence of hardpan.

Successive straw biochar amendments reduce nitrous oxide emissions but do not improve the net ecosystem economic benefit in an alkaline sandy loam under a wheat–maize cropping system

AbstractCrop straw is converted to biochar with subsequent applications to soils as a multi‐benefit strategy for greenhouse gas (GHG) emission mitigation, carbon sequestration, and straw disposal and utilization in intensive agriculture. However, tradeoffs between agronomic, economic, and environmental performance of long‐term agricultural biochar use remain unclear. Using a case study of biochar‐amended alkaline sandy loamy soil, we investigated the effects of field application of straw biochar at 0, 2.25, 6.75, and 11.25 Mg ha−1 to 10 successive wheat and maize crop seasons over five rotation years on crop yield, nitrous oxide (N2O) emissions, soil total organic carbon (TOC), and soil carbon pool (SCP). The net global warming potential (net GWP) and net ecosystem economic benefit (NEEB) were assessed to examine the tension between balancing economic returns and environmental benefits. Results indicated that biochar treatments slightly increased total crop grain yields and greatly reduced the total N2O emissions over five rotation years. The soil total organic carbon content was enhanced while the CO2 emissions during biochar production almost offset the increase in the soil carbon pool. Economic assessment showed that the net ecosystem economic benefit was lowered with enhanced costs of the increasing biochar use under the current low C trade market. These results highlight the promotion of the use of straw biochar in successive applications as a strategy to effectively offset greenhouse gas emissions from agriculture requires optimization of the straw pyrolysis system to reduce the energy consumption and overall biochar costs, and price enhancement of C trade.

Fertilizer nitrogen use efficiency and fates in maize cropping systems across China: Field 15N tracer studies

Maize (Zea mays L.) is a staple crop that is grown worldwide. The heavy use of nitrogen (N) fertilizers in maize cropping systems has resulted in low N use efficiency (NUE) and even caused N pollution in some regions of China. To evaluate the environmental impacts of over-fertilization, it is essential to reveal NUE and the fates of the applied N fertilizers, which can be accurately quantified only by the field 15N tracer technique. In this study, we conducted six on-farm 15N tracer experiments with four in Northeast (NE) China where maize is extensively cropped. We combined the results from these field experiments with previous 15N tracer results (most in the North-Central (NC) region) to estimate the fates of N fertilizer in maize cropping systems throughout China. In total, there were 23 site-year field experiments. We found that, on average, 34%, 35% and 31% of the applied N fertilizers (222 kg N ha−1 on average) was taken up by aboveground biomass, retained in the soil and lost to the environment, respectively. The NUE, as the percentage of 15N removal by aboveground biomass, was much higher in NE China than in NC China (47% vs. 28%, n = 6 and 16, respectively). The regional NUE differences suggested that the overall NUE in the Chinese maize cropping system would be underestimated if only data from NC China were considered. Additionally, NE China had a higher crop N uptake (260 vs. 192 kg N ha−1) and a lower N loss proportion (21% vs. 34%) than NC China. These regional differences were controlled more by soil properties than by climatic factors. In addition to fertilizer N, our 15N results indicated that, on average, 64% of the maize N was derived from soil, implying that native soil N is also an important N source for crop N uptake. Based on the mass balance of N input and N output, exogenous N replenishment to soil N pool consumption is a vital mechanism for maintaining the long-term fertility of the soil. To evaluate the long-term fates and use efficiency of N fertilizer, future research needs to quantify the contribution of N fertilizer to soil N consumption - replenishment.

Residual Effect of Different Sources of Nutrients on Available NPK in Soil after Harvest of Maize in Rice Fallow Maize Cropping System

A field experiment was conducted for two consecutive years (2011-2012 and 2012-2013) on fine texture soils of Agricultural college farm, Bapatla. The experiment was laid out in a randomized block design in kharif season with four treatments. The treatments consisted of M1 (RDF (Recommended dose of fertilizers) - Control), M2 (10t FYM (Farm Yard Manure) ha-1 + RDF), M3 (1.5t vermicompost ha-1 + RDF), M4 (Green manuring + RDF). During the immediate rabi, the experiment was laid out in a split-plot design without disturbing the soil for succeeding maize with the four treatments given to kharif rice as main plot treatments and each of these divided into five sub-plots to receive five levels of fertilizer NPK application viz., N1 - 75% NPK, N2 - 100% NPK, N3 - 125% NPK, N4 - 150% NPK and N5 - 175% NPK for succeeding maize.&#x0D; Data collected on available NPK after harvest of maize crop were significantly increased with the application of 100% NPK in combination with FYM @10t ha-1 to preceding rice crop, irrespective of the NPK levels applied to succeeding maize crop. However, it was on par with that of green manuring together with 100% NPK during both the years of the study.

Expansion of maize production in a semi-arid region of Argentina: Climatic and edaphic constraints and their implications on crop management

The Southwestern Pampas (SWP) is a semi-arid region of Argentina with the presence of a widespread caliche layer that limits soil depth. In this region, maize production has recently expanded with scarce information on appropriate management practices. The objective of this work was to provide an agro-climatic and eco-physiological framework of cultural changes of maize cropping systems of the SWP and the main implications of the climatic and edaphic constraints on crop management decisions. The work combined i) public data of regional maize cultivated area for the period 2008–2015 alongside with farmers’ cropping management trends related to sowing dates and plant population density (PPD); ii) on-field experimental data generated from trials in different sites in the SWP sown at different dates, soil depths and PPDs; and iii) a crop water-economy characterization with a probabilistic approach by means of historical climatic series (identifying the El Niño Southern Oscillation (ENSO) phases) in three locations in the SWP across a longitudinal range between the 800 mm and 600 mm isohyets. In the 2008–2015 period, maize area increased five-fold, median sowing date delayed one month and PPD decreased from ca. 7.2 pl m-2 to 3.4 pl m-2. Late-sown crops (7564 kg ha-1; CV = 19%) out-yielded early-sown crops (5888 kg ha-1; CV = 42%) with less variability across environments. Crop evapotranspiration during the cycle (ETacycle) slightly decreased (P50 = 3–32 mm lower) with the delay of sowing, but the proportion of crop evapotranspiration during the reproductive period was significantly higher. ETacycle of late crops did not vary within PPD, but transpiration per plant decreased with PPD and increased in deep soils, especially at low densities. The impacts of sowing date and PPD did not vary among ENSO phases, not supporting the use of ENSO as a decision criterion for maize management in the SWP.

Managing Tillage Operation and Manure to Restore Soil Carbon Stocks in Wheat–Maize Cropping System

Increasing soil organic matter (SOM) contents improve the resilience of productive soil for future sustainability particularly in poor soil (&lt;1% SOM). This study sought to elucidate how tillage and N fertilizer sources affect soil bulk density, soil organic carbon (SOC) and soil total N (TN) in 0‐ to 20‐cm soil depth. Treatments included minimum till (MT), conventional till (CT), deep till (DT), and twelve N treatments (60 and 120 kg urea N ha−1, 10 and 20 Mg farmyard manure [FYM] ha−1, 10 Mg soybean residue [SR] ha−1and their combinations along with a control). The experiment was designed in randomized complete block design with split plot arrangement. Soil bulk density increased for DT toward the end of the experiment than CT or MT. The sequestration rates of SOC of MT was 22% higher than DT. The FYM retuned more SOC than SR, however SR returned more TN than FYM. Application of FYM as well as SR sequestered more C than urea or control. Conclusively, SOC returned was increased with 10 Mg FYM ha−1along with 30 kg urea N ha−1but TN with 10 Mg SR ha−1in CT plots. This practice can therefore increase soil quality and productivity, and thus is considered a sustainable approach for soils deficient in organic matter.Core IdeasMinimum tillage improved C stock than shallow or deep tillage.The addition of urea increased SOC contents in SR plots than FYM.C Stocks in FYM and SR fertilized plots was about 3‐ to 4‐fold greater than control.Soybean residue build N stock principally in less plowed plots.

Small soil C cycle responses to three years of cover crops in maize cropping systems

Cover crops are touted for their ability to improve many ecosystem functions in annual cropping systems. In addition to water and nutrient retention, cover crops may influence C cycling by increasing total C inputs to the agroecosystem, stimulating microbial populations, altering main crop residue decomposition rate, or changing litter chemistry over time. We assessed whether annual (rye) or perennial (bluegrass) cover crops in maize cropping systems influenced maize residue decomposition (litterbags) or microbial communities (shotgun metagenomics) in soil and litter, and whether these cover crops had an effect on microbially active pools of C: particulate organic matter (POM) C and N, or potentially mineralizable C (PMC) after three years of cover crops. Neither cover crop affected litterbag decay rates or microbial composition relative to no cover crop controls. However, both cover crop types increased PMC indicating that microbially-available C was boosted by cover crops. Total POM and POM-N were higher with bluegrass cover crops. These modest effects of cover crops on dynamic soil C pools suggest the generally positive long-term effects of cover crops on soil protection and nutrient retention are related to incremental shifts in quantity, timing and quality of C inputs.

Spatial management strategies for nitrogen in maize production based on soil and crop data

Nitrogen (N) fertilisation determines maize grain yield (MGY). Precision agriculture (PA) allows matching crop N requirements in both space and time. Two approaches have been suggested for precision N management, i.e. management zones (MZ) delineation and crop remote and proximal sensing (PS). Several studies have demonstrated separately the advantages of these approaches for precision N application. This study evaluated their convenient integration, considering the influence of different PA techniques on MGY, N use efficiency (NUE), and farmer's net return, then providing a practical tool for choosing the fertilisation strategy that best applies in each agro-environment. A multi-site-year experiment was conducted between 2014 and 2016 in Colorado, USA. The trial compared four N management practices: uniform N rate, variable N rate based on MZ (VR-MZ), variable N rate based on PS (VR-PS), and variable N rate based on both PS and MZ (VR-PSMZ), based on their effect on MGY, partial factor productivity (PFPN), and net return above N fertiliser cost (RANC). Maize grain yield and PFPN maximisation conflicted in several situations. Hence, a compromise between obtaining high yield and increasing NUE is needed to enhance the overall sustainability of maize cropping systems. Maximisation of RANC allowed defining the best N fertilisation practice in terms of profitability. The spatial range in MGY is a practical tool for identifying the best N management practice. Uniform N supply was suitable where no spatial pattern was detected. If a high spatial range (>100 m) existed, VR-MZ was the best approach. Conversely, VR-PS performed better when a shorter spatial range (<16 m) was detected, and when maximum variability in crop vigour was observed across the field (range of variation = 0.597) leading to a larger difference in MGY (range of variation = 13.9 Mg ha−1). Results indicated that VR-PSMZ can further improve maize fertilisation for intermediate spatial structures (43 m).

Optimal genotype × environment × management as a strategy to increase grain maize productivity and water use efficiency in water-limited environments and rising temperature

Water limitation is a major concern for the present and future of agriculture, particularly in fragile areas such as arid and semi-arid regions under climate change conditions. In such ecosystems, sustainability of maize production can partially be achieved by investigating the interaction of genotype, environment and management, particularly as effected by climate change. The Agricultural Production Systems sIMulator (APSIM) was applied to assess the effect of future climate change on maize grain yield and water use efficiency in Khuzestan province for two cultivars (as genotype), two seasons (as environment) and nine irrigation regimes (as management). Projections of future climate of Khuzestan was conducted using the baseline period of 1980–2010 and Miroc5 general circulation model for 2040–2070 under two RCPs using The Agricultural Model Intercomparison and Improvement Project (AgMIP) methodology at 15 locations. The simulation results demonstrated that grain yield and water use efficiency will have decreased 6.04% and 5.4%, respectively across the province in 2050 under both RCP4.5 and RCP8.5. This decrease can be mitigated and sustained by adapting a suitable genotype × environment × management interaction. The optimal genotype × environment × management for winter and summer seasons were SC260 × winter sowing × 10-time irrigation per crop season and SC704 × summer sowing × 10-time irrigation per crop season, respectively. Shifting from winter maize cultivation to summer sowing in the future could result in a change in environmental conditions that include a reduced mean temperature (−2.6 °C) and an increase rainfall (81.3 mm) and length of maize growing season (7.9 days). This will reduce water consumption by maize by 185.37 mm, increase water use efficiency by 4.38 kg ha−1 mm−1 and grain yield by 88.32 kg ha−1. The results show that sustainability can be obtained for maize cropping systems through the choice of an optimal genotype × environment × management in the forthcoming period.

Subsurface banding of poultry litter influence on runoff nutrient losses in a no-tillage maize cropping system

Poultry litter (PL) is often used as an alternative nutrient source to inorganic fertilization for crop production in the southeastern US. Historically, PL has been broadcast applied on the soil surface, leaving the nutrients susceptible to runoff. Developments made in recent years allow for placing PL in narrow bands below the soil surface with minimal disturbance. This technological advancement could reduce the transport of P in surface water runoff from fields managed under conservation agricultural systems. Thus, a study was conducted to evaluate the influence of banding PL into a no-tillage corn (Zea Mays L.) field on P loss. Treatments consisted of surface banded PL, subsurface banded PL (3–5 cm below the surface), broadcasted PL, broadcasted commercial fertilizer (CF), and a nonfertilized control. The PL treatments were applied based on an N rate of 168 kg total N ha−1. For the CF, inorganic N was applied at a rate of 168 kg total N ha-1 and P at a rate of 45 kg P ha−1. Runoff events (40 min) were created using rainfall simulations (rainfall was applied at 89 mm hr−1). The greatest losses of dissolved reactive P and inorganic N occurred with the surface broadcast treatments. Subsurface band applying PL reduced P concentration losses and loading in surface water runoff to levels of the control. No differences were observed in runoff volume between treatments. Thus, total P losses mimic those observed for dissolved reactive P concentration in surface water runoff and loads. Approximately 60–80% of the total P concentration was dissolved reactive P regardless of application method. Subsurface band application reduced total P concentration by 95% when compared to surface broadcasted litter. These results show that subsurface band-applied PL can greatly reduce the impact of P loss to the environment when compared to conventional surface-applied PL and CF practices.

Maize Yield Response to Nitrogen Rates and Sources Associated with Azospirillum brasilense

Core Ideas Urea with N‐(n‐butyl thiophosphoric) triamide provided similar effects to conventional urea in tropical edaphoclimatic conditions.Azospirillum brasilense increased maize grain yield, independently of the nitrogen source.Seed inoculation increase maize grain yield even with high nitrogen rates.Inoculation with A. brasilense increases profit in maize production. New studies are needed to optimize the nitrogen amount that can be applied to utilize the Azospirillum brasilense benefits in maize cropping systems. In addition, information regarding the interaction between the urease inhibitor N‐(n‐butyl) thiophosphoric triamide (NBPT) and biological nitrogen fixation (BNF) and how they affect the crop development and yield is also needed. The objective of this study was to evaluate the effect of rates and sources of N in combination with A. brasilense, on leaf chlorophyll index (LCI), N leaf concentration, production components, and maize grain yield in the Brazilian Cerrado region. The study was performed in a Typic Rhodic Hapludox under no‐tillage system. The experimental design was a randomized complete block design with four replications arranged in a 2 × 5 × 2 factorial scheme: two N sources (urea and urea with NBPT) and five N rates (0, 50, 100, 150, and 200 kg ha−1), with and without A. brasilense inoculation. The increase in N rates significantly enhance LCI, N leaf concentration, plant height, ear diameter, mass of 100 grains, and grain yield. No significant differences were observed among the N sources. Inoculation with A. brasilense increased LCI, stem diameter, ear length, and nitrogen use efficiency (NUE), with a positive effect on grain yield. The increase in N rate up to 200 kg ha‐–1 with A. brasilense inoculation increased grain yield, independently of the N source. The application of 100 kg ha−1 of N as urea, with inoculation of A. brasilense produced the highest profit in maize production.

Application of open-path Fourier transform infrared spectroscopy (OP-FTIR) to measure greenhouse gas concentrations from agricultural fields

Abstract. Open-path Fourier transform infrared spectroscopy (OP-FTIR) has often been used to measure hazardous or trace gases from hot point sources (e.g. volcano, industrial, or agricultural facilities) but seldom used to measure greenhouse gases (GHGs) from field-scale sources (e.g. agricultural soils). Closed-path mid-IR laser-based N2O, nondispersive-IR CO2 analysers, and OP-FTIR were used to measure concentrations of N2O and CO2 at a maize cropping system during 9–19 June 2014. To measure N2O and CO2 concentrations accurately, we developed a quantitative method of N2O∕CO2 analysis that minimized interferences from diurnal changes of humidity and temperature. Two chemometric multivariate models, classical least squares (CLS) and partial least squares (PLS), were developed. This study evaluated various methods to generate the single-beam background spectra and different spectral regions for determining N2O and CO2 concentrations from OP-FTIR spectra. A standard extractive method was used to measure the actual path-averaged concentrations along an OP-FTIR optical path in situ, as a benchmark to assess the feasibilities of these quantitative methods. Within an absolute humidity range of 5000–20 000 ppmv and a temperature range of 10–35 ∘C, we found that the CLS model underestimated N2O concentrations (bias =-4.9±3.1 %) calculated from OP-FTIR spectra, and the PLS model improved the accuracy of calculated N2O concentrations (bias =1.4±2.3 %). The bias of calculated CO2 concentrations was -1.0±2.8 % using the CLS model. These methods suggested that environmental variables potentially lead to biases in N2O and CO2 estimations from OP-FTIR spectra and may help OP-FTIR users avoid dependency on extractive methods of calibrations.

Seasonal variations in N2 and N2O emissions from a wheat–maize cropping system

The N losses via denitrification and the N2/N2O emission ratio are highly uncertain, mainly due to methodological difficulties concerning measurement of N2 emissions. Here, we report on seasonal measurements of N2O and N2 emissions from the top soil of a winter wheat–summer maize double-cropping system in the North China Plain. A novel double cylinder soil core method was used to measure N2O and N2 fluxes in situ from a 20-year field experiment with four N fertilizer treatments (0, 200, 400, and 600 kg N ha−1 year−1) and 16 sampling occasions over a 1-year period. The N2-free helium-oxygen atmosphere in the inter-layer between the two cylinders acted as a buffer against N2 diffusion from the atmosphere into the soil core. Total N2O emissions were 0.44, 1.31, 2.19, and 2.23 kg N ha−1 year−1, and total N2 emissions were 8.3, 20.0, 22.5, and 24.7 kg N ha−1 year−1 from the N0, N200, N400, and N600 treatments, respectively. The N2/N2O emission ratio ranged from 2 to 136, indicating that N2 was the dominant gas. The N2/N2O ratio was much higher in summer than in winter, and was inversely related to fertilizer N application. Fluxes of N2 were statistically related to soil temperature and concentrations of NO3−-N and DOC in soil extracts, while N2O fluxes were related to soil water content and concentrations of NO3−-N and exchangeable NH4+ in soil extracts. The N2/N2O ratio was related to soil temperature and exchangeable NH4+ and NO3−-N concentrations. Our study provides new insights on variations of the N2/N2O emission ratio in agroecosystems, and shows the importance of seasonal measurements.