The interaction of seasonal rainfall and nitrogen fertiliser rate on soil N2O emission, total N loss and crop yield of dryland sorghum and sunflower grown on sub-tropical Vertosols

Summer crop production on slow-draining Vertosols in a sub-tropical climate has the potential for large emissions of soil nitrous oxide (N2O) from denitrification of applied nitrogen (N) fertiliser. While it is well established that applying N fertiliser will increase N2O emissions above background levels, previous research in temperate climates has shown that increasing N fertiliser rates can increase N2O emissions linearly, exponentially or not at all. Little such data exists for summer cropping in sub-tropical regions. In four field experiments at two locations across two summers, we assessed the impact of increasing N fertiliser rate on both soil N2O emissions and crop yield of grain sorghum (Sorghum bicolor L.) or sunflower (Helianthus annuus L.) in Vertosols of sub-tropical Australia. Rates of N fertiliser, applied as urea at sowing, included a nil application, an optimum N rate and a double-optimum rate. Daily N2O fluxes ranged from –3.8 to 2734g N2O-Nha–1day–1 and cumulative N2O emissions ranged from 96 to 6659g N2O-Nha–1 during crop growth. Emissions of N2O increased with increased N fertiliser rates at all experimental sites, but the rate of N loss was five times greater in wetter-than-average seasons than in drier conditions. For two of the four experiments, periods of intense rainfall resulted in N2O emission factors (EF, percent of applied N emitted) in the range of 1.2–3.2%. In contrast, the EFs for the two drier experiments were 0.41–0.56% with no effect of N fertiliser rate. Additional 15N mini-plots aimed to determine whether N fertiliser rate affected total N lost from the soil–plant system between sowing and harvest. Total 15N unaccounted was in the range of 28–45% of applied N and was presumed to be emitted as N2O+N2. At the drier site, the ratio of N2 (estimated by difference)to N2O (measured) lost was a constant 43%, whereas the ratio declined from 29% to 12% with increased N fertiliser rate for the wetter experiment. Choosing an N fertiliser rate aimed at optimum crop production mitigates potentially high environmental (N2O) and agronomic (N2+N2O) gaseous N losses from over-application, particularly in seasons with high intensity rainfall occurring soon after fertiliser application.

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Effects of Changing Fertilization since the 1980s on Nitrogen Runoff and Leaching in Rice–Wheat Rotation Systems, Taihu Lake Basin

Water ◽

10.3390/w12030886 ◽

2020 ◽

Vol 12 (3) ◽

pp. 886

Author(s):

Yaqin Diao ◽

Hengpeng Li ◽

Sanyuan Jiang ◽

Xinyan Li

Keyword(s):

Algal Blooms ◽

Field Experiments ◽

Taihu Lake ◽

Crop Yields ◽

Fertilization Rate ◽

Freshwater Ecosystems ◽

Lake Basin ◽

N Loss ◽

N Losses ◽

Total N

The nitrogen (N) loss associated with intensive agricultural activities is a significant cause of eutrophication and algal blooms in freshwater ecosystems. Taihu Lake has experienced serious surface water quality deterioration and eutrophication problems since the 1980s. The objective of this study is to examine the effect of fertilization changes since the 1980s on the N loss with runoff and leaching in the rice–wheat cropping rotation system. According to the results published in the literature since the 1980s, we set up four fertilization scenarios—N1980s: a fertilization rate of 350 kg N·ha−1·year−1 with 30% in manure fertilization to simulate fertilization in the 1980s; NA1990s: a fertilization rate of 500 kg N·ha−1·year−1 with 10% in manure fertilization to simulate fertilization in the early 1990s; NL1990s: fertilization rate of 600 kg N·ha−1·year−1 with 10% in manure fertilization to simulate fertilization in the late 1990s; and N2000s: fertilization rate of 550 kg N·ha−1·year−1 with all chemicals to simulate fertilization in the 2000s. Then, we calibrated and validated the DNDC (denitrification–decomposition) model through field experiments in two rice–wheat rotation seasons from November 2011 to October 2013 and simulated the N loss with runoff and leaching since the 1980s. The results show that N losses with leaching in the four periods (N 1980s, NA1990s, NL1990s, and N2000s) were 5.2 ± 2.1, 9.4 ± 3.2, 14.4 ± 4.6 and 13.5 ± 4.6 kg N·ha−1·year−1, respectively. N losses with surface runoff were 7.9 ± 3.9, 18.3 ± 7.2, 25.4 ± 10.2, and 26.5 ± 10.6 kg N·ha−1·year−1, respectively. The total N loss through runoff and leaching showed an increasing trend from 1980 to the late 1990s, when it reached its peak. The increase in N export to water due to fertilizer application occurs mainly during the rainy season from March to August, and especially from June to August, when rainfall events and intensive rice fertilization activities are frequent. After the 1990s, when the fertilizer rate was above 500 kg N·ha−1·year−1, the crop yields no longer increased significantly, which indicates that the optimized fertilization rate to balance crop yields and N loss to water is lower than 500 kg N·ha−1·year−1. The increase in fertilizer use has been unnecessary since the early 1990s, and at least about 30% of the N loss could have been prevented without reducing crop yields.

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Direct and Indirect Effects of Urease and Nitrification Inhibitors on N2O-N Losses from Urea Fertilization to Winter Wheat in Southern Germany

Atmosphere ◽

10.3390/atmos11080782 ◽

2020 ◽

Vol 11 (8) ◽

pp. 782 ◽

Cited By ~ 1

Author(s):

Yuncai Hu ◽

Manuela P. Gaßner ◽

Andreas Weber ◽

Martine Schraml ◽

Urs Schmidhalter

Keyword(s):

Winter Wheat ◽

Field Experiments ◽

N2o Emission ◽

N Fertilization ◽

N Fertilizer ◽

N2o Emissions ◽

Nitrification Inhibitors ◽

N Losses ◽

Calcium Ammonium Nitrate ◽

Southern Germany

Urea (U) is the most important nitrogen (N) fertilizer in agriculture worldwide, and as N fertilizer can result in large gaseous losses of NH3 and N2O. Thus, urease inhibitors (UIs) and nitrification inhibitors (NIs) have been coupled with U fertilizers to mitigate NH3 and N2O emissions. However, it is still unclear whether adding NIs and/or UIs to U stimulates other pollutants, while reducing one pollutant. Furthermore, part of the NH3 deposition to earth is converted to N2O, leading to indirect N2O emission. To estimate direct and indirect effect of UIs and NIs on the N2O-N and NH3-N losses from U; therefore, we analyzed multi-year field experiments from the same site during 2004 to 2005 and 2011 to 2013. The field experiments with U fertilization with or without UI (IPAT, N-isopropoxycarbonyl phosphoric acid triamide) and NI (DCD/TZ, Dicyandiamide/1H-1, 2, 4-Triazol) in winter wheat and with calcium ammonium nitrate (CAN) were conducted in southern Germany. Fluxes of NH3 or N2O emissions were determined following each split N fertilization in separate experiments on the same site. Our results showed that U with NIs considerably reduced N2O emissions, and adding UIs decreased NH3 emissions. However, the effect on N2O emissions exerted by (U + UIs) or (U + UIs + NIs) was inconsistent. In contrast to the treatment of (U + UIs + NIs), the addition of NIs alone to U stimulated NH3 emission compared to treatment with U. When 1% indirect N2O emission from NH3 (IPCC emission factor (EF4)) was considered to estimate the indirect N2O emission, total N2O emissions from (U + NIs) were approximately 29% compared to that from U alone and 36% compared to that from (U + UI), indicating that indirect N2O emission from NH3 induced by NIs may be negligible.

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The Pitfalls of Relating Weeds, Herbicide Use, and Crop Yield: Don't Fall Into the Trap! A Critical Review

Frontiers in Agronomy ◽

10.3389/fagro.2020.615470 ◽

2020 ◽

Vol 2 ◽

Author(s):

Nathalie Colbach ◽

Sandrine Petit ◽

Bruno Chauvel ◽

Violaine Deytieux ◽

Martin Lechenet ◽

...

Keyword(s):

Crop Yield ◽

Weed Management ◽

Crop Production ◽

Yield Loss ◽

Crop Yields ◽

Cropping Systems ◽

Crop Productivity ◽

Arable Farming ◽

Herbicide Use ◽

The Impact

The growing recognition of the environmental and health issues associated to pesticide use requires to investigate how to manage weeds with less or no herbicides in arable farming while maintaining crop productivity. The questions of weed harmfulness, herbicide efficacy, the effects of herbicide use on crop yields, and the effect of reducing herbicides on crop production have been addressed over the years but results and interpretations often appear contradictory. In this paper, we critically analyze studies that have focused on the herbicide use, weeds and crop yield nexus. We identified many inconsistencies in the published results and demonstrate that these often stem from differences in the methodologies used and in the choice of the conceptual model that links the three items. Our main findings are: (1) although our review confirms that herbicide reduction increases weed infestation if not compensated by other cultural techniques, there are many shortcomings in the different methods used to assess the impact of weeds on crop production; (2) Reducing herbicide use rarely results in increased crop yield loss due to weeds if farmers compensate low herbicide use by other efficient cultural practices; (3) There is a need for comprehensive studies describing the effect of cropping systems on crop production that explicitly include weeds and disentangle the impact of herbicides from the effect of other practices on weeds and on crop production. We propose a framework that presents all the links and feed-backs that must be considered when analyzing the herbicide-weed-crop yield nexus. We then provide a number of methodological recommendations for future studies. We conclude that, since weeds are causing yield loss, reduced herbicide use and maintained crop productivity necessarily requires a redesign of cropping systems. These new systems should include both agronomic and biodiversity-based levers acting in concert to deliver sustainable weed management.

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Soil Type Modifies the Impacts of Warming and Snow Exclusion on Carbon and Nutrient Losses

10.21203/rs.3.rs-1139295/v1 ◽

2021 ◽

Author(s):

Stephanie M. Juice ◽

Paul G. Schaberg ◽

Alexandra M. Kosiba ◽

Carl E. Waite ◽

Gary J. Hawley ◽

...

Keyword(s):

Climate Change ◽

Nutrient Cycling ◽

Soil Type ◽

Soil Characteristics ◽

Nutrient Loss ◽

Climate Projections ◽

Nutrient Losses ◽

N Losses ◽

Total N ◽

The Impact

Abstract The varied and wide-reaching impacts of climate change are occurring across heterogeneous landscapes. Despite the known importance of soils in mediating biogeochemical nutrient cycling, there is little experimental evidence of how soil characteristics may shape ecosystem response to climate change. Our objective was to clarify how soil characteristics modify the impact of climate changes on carbon and nutrient leaching losses in temperate forests. We therefore conducted a field-based mesocosm experiment with replicated warming and snow exclusion treatments on two soils in large (2.4 m diameter), in-field forest sapling mesocosms. We found that nutrient loss responses to warming and snow exclusion treatments frequently varied substantially by soil type. Indeed, in some cases, soil type nullified the impact of a climate treatment. For example, warming and snow exclusion increased nitrogen (N) losses on fine soils by up to four times versus controls, but these treatments had no impact on coarse soils. Generally, the coarse textured soil, with its lower soil-water holding capacity, had higher nutrient losses (e.g., 12-17 times more total N loss from coarse than fine soils), except in the case of phosphate, which had consistently higher losses (23-58%) from the finer textured soil. Furthermore, the mitigation of nutrient loss by increasing tree biomass varied by soil type and nutrient. Our results suggest that potentially large biogeochemical responses to climate change are strongly mediated by soil characteristics, providing further evidence of the need to consider soil properties in Earth system models for improving nutrient cycling and climate projections.

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Recovery of 15N-labelled fertilizers applied to barley on two artificially eroded soils in north-central Alberta

Canadian Journal of Soil Science ◽

10.4141/s97-071 ◽

1998 ◽

Vol 78 (2) ◽

pp. 377-383 ◽

Cited By ~ 2

Author(s):

R. Pradhan ◽

R. C. Izaurralde ◽

S. S. Malhi ◽

M. Nyborg

Keyword(s):

Field Experiments ◽

Water Saturation ◽

Nutrient Use Efficiency ◽

N Loss ◽

Hordeum Vulgare L ◽

N Losses ◽

North Central ◽

Major Mechanism ◽

Erosion Level ◽

N Management

Soil erosion induces variability in soil properties which may influence nutrient use efficiency. A 2-yr field study was conducted with the following objectives: (1) to determine the recovery of 15N-labelled fertilizers applied to barley growing on artificially eroded soil, and (2) to compare N losses from nitrate- and ammonia-based N fertilizers. Field experiments were conducted in north-central Alberta in 1991 and 1992 on an Orthic Gray Luvisol (Site 1) and on an Eluviated Black Chernozem (Site 2) soil. At each site, a factorial experiment of three levels of artificial erosion (0, 10 and 20 cm) and three N sources (KNO3, urea, and control) was laid out as a split-plot design with four replications. The 15N-labelled fertilizers (5.63 atom % abundance) were banded in June 1991 at 150 kg N ha−1 within 46-cm by 46-cm steel frame microplots. The proportion of added N recovered by barley (Hordeum vulgare L.) was not affected by erosion level. Periodical water saturation and NO3− availability suggested denitrification as a major mechanism of N loss. The N losses ranged from 12 to 51 g N ha−1 in 1991 and 20 to 80 kg N ha−1 over the 2-yr period, but the N losses did not relate to erosion level. The N losses after 2 yr were greater from KNO3 than from urea at Site 1. Most of the added 15N was found in the surface 0- to 15-cm layer, but amounts of 15N were detected in the 15- to 30-cm or 30- to 45-cm layers. The results call for continued development of N management techniques geared to optimize crop growth and minimize losses from fields. Key words: Artificial erosion, barley, fate of applied N, 15N-labelled fertilizers, N immobilization, N loss

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A two-year field assessment on the effect of slow release of nitrogenous fertiliser on N2O emissions from a wheat cropping system

Soil Research ◽

10.1071/sr16001 ◽

2017 ◽

Vol 55 (2) ◽

pp. 191 ◽

Cited By ~ 5

Author(s):

Nirmali Bordoloi ◽

K. K. Baruah

Keyword(s):

Field Experiments ◽

Plant Biomass ◽

Global Climate ◽

Cropping System ◽

N2o Emission ◽

N2o Emissions ◽

Wheat Field ◽

Grain Productivity ◽

Coated Urea ◽

Fertiliser Application

Nitrous oxide (N2O) is considered a major contributor to global climate change in addition to carbon dioxide and methane. A significant quantity of N2O emission originates from agriculture, largely from high rates of fertiliser application. We studied N2O emissions from wheat field to evaluate the effect of different forms of fertilisers and the potential for emission reduction. Field experiments were conducted for two consecutive seasons with four fertilisers, namely inorganic fertiliser (NPK), starch-coated urea (SCU), neem-coated urea (NCU), and urea alone (UA) in a tropical wheat ecosystem. Gas samples were collected from the field at weekly intervals using the static chamber technique and analysed with a gas chromatograph. The cumulative N2O emissions were higher from the NPK amended field (3.19kgN2O-Nha–1) followed by UA (3.05kg N2O-N ha–1). The SCU, NCU, and UA amendments decreased the total N2O emissions by 23%, 12%, and 4%, respectively (P<0.05) over the application of NPK. The results indicate a good correlation of N2O emissions with soil organic carbon, soil NO3–-N, NH4+-N, leaf area, and plant biomass. The application of SCU resulted in higher grain productivity and was the most effective substitute for conventional fertiliser in terms of reducing N2O emissions from a tropical wheat ecosystem.

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EFFECT OF ADDED MONOCALCIUM PHOSPHATE MONOHYDRATE AND AERATION ON NITROGEN RETENTION BY LIQUID HOG MANURE

Canadian Journal of Soil Science ◽

10.4141/cjss87-065 ◽

1987 ◽

Vol 67 (3) ◽

pp. 687-692 ◽

Cited By ~ 7

Author(s):

A. F. MACKENZIE ◽

J. S. TOMAR

Keyword(s):

Sus Scrofa ◽

Crop Production ◽

Nitrogen Retention ◽

N Losses ◽

N Content ◽

Total N ◽

N Retention ◽

Monocalcium Phosphate ◽

Hog Manure ◽

Sus Scrofa Domesticus

Retention of nitrogen in manure to be used for crop production and to reduce environmental pollution is an essential management component. The effects of monocalcium phosphate monohydrate (MCPM) and aeration on N retention in liquid hog (Sus scrofa domesticus) manure (LHM) were investigated under laboratory conditions. The manure received 0, 20 or 40 g of MCPM kg−1 of LHM (0, 250 or 500 g MCPM kg−1 manure solids) and was incubated over a 15-d period with and without aeration. Manure pH decreased with added MCPM and then remained constant, but pH increased with time when MCPM was not added. Losses of NH3 from hog manure were significantly reduced by added MCPM, but increased significantly with aeration where MCPM was not added to the manure. The NH4-N content of LHM was higher where MCPM was added to the manure. Conversely, the NH4-N content tended to decrease with aeration in the absence of MCPM. Total N content of LHM was significantly decreased where MCPM was not added to the manure. Aeration had no significant effect on total N. It was concluded that addition of MCPM can increase the NH4-N content of LHM by decreasing NH3-N losses through acidification of the manure. Key words: Aeration, Ca(H2PO4)2∙H2O, hog manure, pH reduction, NH3 loss

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The effect of work level and dietary intake on sweat nitrogen losses in a hot climate

British Journal Of Nutrition ◽

10.1079/bjn19720124 ◽

1972 ◽

Vol 27 (3) ◽

pp. 543-552 ◽

Cited By ~ 5

Author(s):

J. S. Weiner ◽

J. O. C. Willson ◽

Hamad El-Neil ◽

Erica F. Wheeler

Keyword(s):

Normal Diet ◽

Physical Work ◽

N Loss ◽

N Losses ◽

Total N ◽

Adequate Diet ◽

N Concentration ◽

Hot Climate ◽

Rate Of Increase ◽

Work Level

1. Nitrogen intakes, and N output in urine, faeces and sweat have been measured in six young Tanzanian men who were accustomed to a hot climate. The measurements were done while the subjects were receiving first a normal and then a low-N diet; and when they were performing moderate physical work, and had undergone a period of acclimatization.2. When the subject were acclimatized and working on a normal diet, their sweat output increased, with a fall in its N concentration. Total sweat N loss increased from an average of 0.10 to 0.71 g/d.3. The effect of the low-N diet was to decrease both the sweat N concentration, and the rate of increase of total N loss in sweat, as sweat volume increased.4. It is estimated that maximum sweat N losses would not exceed 1 g/d on an adequate diet, or 0.5 g/d on a low-protein diet. Our results provide no basis for recommending extra protein allowances to cover sweat N losses for workers in tropical climates.

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Smallholder African farms in western Kenya have limited greenhouse gas fluxes

Biogeosciences Discussions ◽

10.5194/bgd-12-15301-2015 ◽

2015 ◽

Vol 12 (18) ◽

pp. 15301-15336 ◽

Cited By ~ 3

Author(s):

D. E. Pelster ◽

M. C. Rufino ◽

T. Rosenstock ◽

J. Mango ◽

G. Saiz ◽

...

Keyword(s):

Greenhouse Gas ◽

Crop Production ◽

Crop Yields ◽

N Uptake ◽

Ghg Emissions ◽

Sub Saharan Africa ◽

N2o Emissions ◽

Vegetation Types ◽

Western Kenya ◽

The Impact

Abstract. Few field studies examine greenhouse gas (GHG) emissions from African agricultural systems resulting in high uncertainty for national inventories. We provide here the most comprehensive study in Africa to date, examining annual CO2, CH4 and N2O emissions from 59 plots, across different vegetation types, field types and land classes in western Kenya. The study area consists of a lowland area (approximately 1200 m a.s.l.) rising approximately 600 m to a highland plateau. Cumulative annual fluxes ranged from 2.8 to 15.0 Mg CO2-C ha−1, −6.0 to 2.4 kg CH4-C ha−1 and −0.1 to 1.8 kg N2O-N ha−1. Management intensity of the plots did not result in differences in annual fluxes for the GHGs measured (P = 0.46, 0.67 and 0.14 for CO2, N2O and CH4 respectively). The similar emissions were likely related to low fertilizer input rates (≤ 20 kg ha−1). Grazing plots had the highest CO2 fluxes (P = 0.005); treed plots were a larger CH4 sink than grazing plots (P = 0.05); while N2O emissions were similar across vegetation types (P = 0.59). This case study is likely representative for low fertilizer input, smallholder systems across sub-Saharan Africa, providing critical data for estimating regional or continental GHG inventories. Low crop yields, likely due to low inputs, resulted in high (up to 67 g N2O-N kg−1 aboveground N uptake) yield-scaled emissions. Improving crop production through intensification of agricultural production (i.e. water and nutrient management) may be an important tool to mitigate the impact of African agriculture on climate change.

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Effect of legume intercropping on N<sub>2</sub>O emissions and CH<sub>4</sub> uptake during maize production in the Great Rift Valley, Ethiopia

Biogeosciences ◽

10.5194/bg-17-345-2020 ◽

2020 ◽

Vol 17 (2) ◽

pp. 345-359

Author(s):

Shimelis Gizachew Raji ◽

Peter Dörsch

Keyword(s):

Rift Valley ◽

Crop Production ◽

Growing Season ◽

Maize Yield ◽

Sub Saharan Africa ◽

Ethiopian Rift ◽

N2o Emissions ◽

Mineral N ◽

Total N ◽

N Input

Abstract. Intercropping with legumes is an important component of climate-smart agriculture (CSA) in sub-Saharan Africa, but little is known about its effect on soil greenhouse gas (GHG) exchange. A field experiment was established at Hawassa in the Ethiopian rift valley, comparing nitrous oxide (N2O) and methane (CH4) fluxes in minerally fertilized maize (64 kg N ha−1) with and without Crotalaria (C. juncea) or lablab (L. purpureus) as intercrops over two growing seasons. To study the effect of intercropping time, intercrops were sown either 3 or 6 weeks after maize. The legumes were harvested at flowering, and half of the aboveground biomass was mulched. In the first season, cumulative N2O emissions were largest in 3-week lablab, with all other treatments being equal to or lower than the fertilized maize mono-crop. After reducing mineral N input to intercropped systems by 50 % in the second season, N2O emissions were comparable with the fully fertilized control. Maize-yield-scaled N2O emissions in the first season increased linearly with aboveground legume N yield (p=0.01), but not in the second season when early rains resulted in less legume biomass because of shading by maize. Growing-season N2O-N emission factors varied from 0.02 % to 0.25 % in 2015 and 0.11 % to 0.20 % in 2016 of the estimated total N input. Growing-season CH4 uptake ranged from 1.0 to 1.5 kg CH4-C ha−1, with no significant differences between treatments or years but setting off the N2O-associated emissions by up to 69 %. Our results suggest that leguminous intercrops may increase N2O emissions when developing large biomass in dry years but, when mulched, can replace part of the fertilizer N in normal years, thus supporting CSA goals while intensifying crop production in the region.

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