scholarly journals Effect of Deficit Irrigation on Nitrogen Uptake of Sunflower in the Low Desert Region of California

Water ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 2340 ◽  
Author(s):  
Mohamed Galal Eltarabily ◽  
John M. Burke ◽  
Khaled M. Bali
Keyword(s):  
Soil Moisture ◽  
Irrigation Water ◽  
Soil Profile ◽  
Deficit Irrigation ◽  
Crop Production ◽  
N Uptake ◽  
Sprinkler Irrigation ◽  
Growing Season ◽  
Total N ◽  
Irrigation Practices

Nitrogen (N) accounts for more than 80% of the total mineral nutrients absorbed by plants and it is the most widely limiting element for crop production, particularly under water deficit conditions. For a comprehensive understanding of sunflower Helianthus annuus N uptake under deficit irrigation conditions, experimental and numerical simulation studies were conducted for full (100% ETC) and deficit (65% ETC) irrigation practices under the semi-arid conditions of the Imperial Valley, California, USA. Plants were established with overhead sprinkler irrigation before transitioning to subsurface drip irrigation (SDI). Based on pre-plant soil N testing, 39 kg ha−1 of N and 78 kg ha−1 of P were applied as a pre-plant dry fertilizer in the form of monoammonium phosphate (MAP) and an additional application of 33 kg ha−1 of N from urea ammonium nitrate (UAN-32) liquid fertilizer was made during the growing season. Soil samples at 15-cm depth increments to 1.2 m (8 layers, 15 cm each) were collected prior to planting and at three additional time points from two locations each in the full and deficit irrigation treatments. We used HYDRUS/2D for the simulation in this study and the model was calibrated for the soil moisture parameters (θs and θr), the rate constant factors of nitrification (the sensitive parameter) in the liquid and solid states (μw,3, and μs,3). The HYDRUS model predicted cumulative root water uptake fluxes of 533 mm and 337 mm for the 100% ETC and 65% ETC, respectively. The simulated cumulative drainage depths were 23.7 mm and 20.4 mm for the 100% ETC and 65% ETC which represented only 4% and 5% of the applied irrigation water, respectively. The soil wetting profile after SDI irrigation was mostly around emitters for the last four SDI irrigation events, while the maximum values of soil moisture in the top 30 cm of the soil profile were 0.262 cm3 cm−3 and 0.129 cm3 cm−3 for 100% ETC and 65% ETC, respectively. The 16.5 kg ha−1 (NH2)2CO (50% of the total N) that was applied during the growing season was completely hydrolyzed to NH4+ within 7 days of application, while 4.36 mg cm−1 cumulative decay was achieved by the end of the 98-day growing season. We found that 86% of NH4+ (74.25 mg cm−1) was nitrified to NO3− while 14% remained in the top 50 cm of the soil profile. The denitrification and free drainage of NO3− were similar for 100% ETC and 65% ETC, and the maximum nitrate was drained during the sprinkler irrigation period. By the end of the growing season, 30.8 mg cm−1 of nitrate was denitrified to N2 and the reduction of nitrate plant uptake was 17.1% for the deficit irrigation section as compared to the fully irrigated side (19.44 mg cm−1 vs. 16.12 mg cm−1). This reduction in N uptake due to deficit irrigation on sunflower could help farmers conserve resources by reducing the amount of fertilizer required if deficit irrigation practices are implemented due to the limited availability of irrigation water.

scholarly journals Feasibility of Moderate Deficit Irrigation as a Water Conservation Tool in California’s Low Desert Alfalfa

Agronomy ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1640
Author(s):  
Ali Montazar ◽  
Oli Bachie ◽  
Dennis Corwin ◽  
Daniel Putnam
Keyword(s):  
Soil Moisture ◽  
Irrigation Water ◽  
Water Conservation ◽  
Deficit Irrigation ◽  
Dry Matter ◽  
Yield Reduction ◽  
Dry Matter Yield ◽  
Water Deficits ◽  
Wide Range ◽  
Irrigation Practices

Irrigation management practices that reduce water use with acceptable impacts on yield are important strategies to cope with diminished water supplies and generate new sources of water to transfer for other agricultural uses, and urban and environmental demands. This study was intended to assess the effects of moderate water deficits, with the goal of maintaining robust alfalfa (Medicago sativa L.) yields, while conserving on-farm water. Data collection and analysis were conducted at four commercial fields over an 18-month period in the Palo Verde Valley, California, from 2018–2020. A range of deficit irrigation strategies, applying 12.5–33% less irrigation water than farmers’ normal irrigation practices was evaluated, by eliminating one to three irrigation events during selected summer periods. The cumulative actual evapotranspiration measured using the residual of energy balance method across the experimental sites, ranged between 2,031 mm and 2.202 mm, over a 517-day period. An average of 1.7 and 1.0 Mg ha−1 dry matter yield reduction was observed under 33% and 22% less applied water, respectively, when compared to the farmers’ normal irrigation practice in silty loam soils. The mean dry matter yield decline varied from 0.4 to 0.9 Mg ha−1 in a clay soil and from 0.3 to 1.0 Mg ha−1 in a sandy loam soil, when irrigation water supply was reduced to 12.5% and 25% of normal irrigation levels, respectively. A wide range of conserved water (83 to 314 mm) was achieved following the deficit irrigation strategies. Salinity assessment indicated that salt buildup could be managed with subsequent normal irrigation practices, following deficit irrigations. Continuous soil moisture sensing verified that soil moisture was moderately depleted under deficit irrigation regimes, suggesting that farmers might confidently refill the soil profile following normal practices. Stand density was not affected by these moderate water deficits. The proposed deficit irrigation strategies could provide a reliable amount of water and sustain the economic viability of alfalfa production. However, data from multiple seasons are required to fully understand the effectiveness as a water conservation tool and the long-term impacts on the resilience of agricultural systems.

Impact of Sprinkler Irrigation Amount and Rotation On Peanut Yield

2004 ◽  
Vol 31 (2) ◽  
pp. 108-113 ◽  
Author(s):  
M. C. Lamb ◽  
M. H. Masters ◽  
D. Rowland ◽  
R. B. Sorensen ◽  
H. Zhu ◽  
...  
Keyword(s):  
Crop Rotation ◽  
Irrigation Water ◽  
Crop Production ◽  
Urban Expansion ◽  
Sprinkler Irrigation ◽  
Growing Season ◽  
Irrigation Amount ◽  
Pod Yield ◽  
One Year ◽  
Rotation Sequence

Abstract Irrigated hectares for crop production in Georgia increased from 70,875 ha in 1970 to 587,250 in 2000. The majority of the increase was planted in peanut, corn, and cotton. In 1970, these crops accounted for 40,500 of Georgia's irrigated hectares, and in 2000, these crops totaled 465,750 irrigated hectares. Simultaneously, demand for water resources due to urban expansion and interstate litigation coupled with repeated drought are collectively threatening irrigation water supplies in the southeast U.S. peanut producing regions. A study was conducted during the 2001 to 2003 crop years to quantify the impacts of reduced irrigation amounts and different crop rotation sequences including peanut, corn, and cotton. On average, irrigated peanut pod yield was significantly increased by 906 kg/ha as compared to nonirrigated peanut yield. The affect of crop rotation on peanut yield was also significant. One year out of peanuts, in either corn or cotton, increased irrigated peanut yield an average of 1072 kg/ha over continuous peanut. Two years out of peanuts, in either corn or cotton, increased irrigated peanut yield an average of 2333 kg/ha over continuous peanut. In nonirrigated peanuts, crop rotation sequence had less affect on pod yield than did precipitation during the growing season.

scholarly journals Impact of Deficit Irrigation on Shallow Saline Groundwater Contribution and Sunflower Productivity in the Imperial Valley, California

Water ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 571
Author(s):  
Mohamed Galal Eltarabily ◽  
John M. Burke ◽  
Khaled M. Bali
Keyword(s):  
Irrigation Water ◽  
Deficit Irrigation ◽  
Growing Season ◽  
Yield Reduction ◽  
Growth Stages ◽  
Crop Evapotranspiration ◽  
Imperial Valley ◽  
Saline Groundwater ◽  
Irrigation Treatments ◽  
Groundwater Contribution

Yield and production functions of sunflower (Helianthus annuus) were evaluated under full and deficit irrigation practices with the presence of shallow saline groundwater in a semi-arid region in the Imperial Valley of southern California, USA. A growing degree day (GDD) model was utilized to estimate the various growth stages and schedule irrigation events throughout the growing season. The crop was germinated and established using overhead irrigation prior to the use of a subsurface drip irrigation (SDI) system for the remainder of the growing season. Four irrigation treatments were implemented: full irrigation (100% full sunflower crop evapotranspiration, ETC), two reduced irrigation scenarios (95% ETC and 80% ETC), and a deficit irrigation scenario (65% ETC). The salinity of the irrigation water (EC) (Colorado River water) was nearly constant at 1.13 dS·m−1 during the growing season. The depth to groundwater and groundwater salinity (ECGW) were continuously monitored in five 3 m deep observation wells. Depth to groundwater fluctuated slightly under the full and reduced irrigation treatments, but drastically increased under deficit irrigation, particularly toward the end of the growing season. Estimates of ECGW ranged from 7.34 to 12.62 dS·m−1. The distribution of soil electrical conductivity (ECS) and soil matric potential were monitored within the active root zone (120 cm) at selected locations in each of the four treatments. By the end of the experiment, soil salinity (ECS) across soil depths ranged from 1.80 to 6.18 dS·m−1. The estimated groundwater contribution to crop evapotranspiration was 9.03 cm or approximately 16.3% of the ETC of the fully irrigated crop. The relative yields were 91.8%, 82.4%, and 83.5% for the reduced (95% and 80% ETC) and deficit (65% ETC) treatments, respectively, while the production function using applied irrigation water (IW) was: yield = 0.0188 × (IW)2 − 15.504 × IW + 4856.8. Yield reduction in response to water stress was attributed to a significant reduction in both seed weight and the number of seed produced resulting in overall average yields of 2048.9, 1879.9, 1688.1, and 1710.3 kg·ha−1 for the full, both reduced, and deficit treatments, respectively. The yield response factor, ky, was 0.63 with R2 = 0.745 and the irrigation water use efficiencies (IWUE) were 3.70, 3.57, 3.81, and 4.75 kg·ha−1·mm−1 for the full, reduced, and deficit treatments, respectively. Our results indicate that sunflowers can sustain the implemented 35% deficit irrigation with root water uptake from shallow groundwater in arid regions with a less than 20% reduction in yield.

scholarly journals Fertilizer Placement Effects on Soil Nitrogen and Use by Drip-irrigated and Plastic-mulched Tomatoes

HortScience ◽  
1990 ◽  
Vol 25 (7) ◽  
pp. 767-769 ◽  
Author(s):  
Wilton P. Cook ◽  
Douglas C. Sanders
Keyword(s):  
Soil Moisture ◽  
N Uptake ◽  
Fruit Size ◽  
Infiltration Rate ◽  
Moisture Level ◽  
Plastic Mulch ◽  
Fertilizer Placement ◽  
Total N ◽  
Soil Moisture Level ◽  
N Concentration

The effects of fertilizer placement and soil moisture level on soil N movement, uptake, and use by tomato plants (Lycopersicon esculentum Mill) grown with drip irrigation and plastic mulch were evaluated at two locations on two types of sandy soils. Broadcast or band fertilizer placement had no effect on fruit size, fruit number, or total yield. Fruit size was increased at one location, and the incidence of blossom-end rot was decreased by increased frequency of irrigation. Nitrate-N distribution within the bed was not affected by initial N placement. In the soil with a rapid infiltration rate, NO3-N levels in the center of the bed were always low, with highest concentration observed in the areas of the bed most distant from the drip tube. In the soil with the slower infiltration rate, NO3-N concentrations were more uniform throughout the bed, with highest concentrations in the bed center: Increasing soil moisture levels (–20 kPa vs. –30 kPa) resulted in increased leaching and reduced NO3-N concentration throughout the bed. Foliage N concentration was not affected by N placement, but decreased seasonally. Total N uptake by the above-ground portion of the plants was not affected by fertilizer placement or soil moisture level.

scholarly journals Estimating irrigation water use over the contiguous United States by combining satellite and reanalysis soil moisture data

2018 ◽  
Author(s):  
Felix Zaussinger ◽  
Wouter Dorigo ◽  
Alexander Gruber ◽  
Angelica Tarpanelli ◽  
Paolo Filippucci ◽  
...  
Keyword(s):  
Water Management ◽  
United States ◽  
Soil Moisture ◽  
Water Use ◽  
Irrigation Water ◽  
Soil Layer ◽  
Data Set ◽  
Soil Moisture Data ◽  
Irrigation Water Use ◽  
Irrigation Practices

Abstract. Effective agricultural water management requires accurate and timely information on the availability and use of irrigation water. However, most existing information on irrigation water use (IWU) lacks the objectivity and spatio-temporal representativeness needed for operational water management and meaningful characterisation of land-climate interactions. Although optical remote sensing has been used to map the area affected by irrigation, it does not physically allow for the estimation of the actual amount of irrigation water applied. On the other hand, microwave observations of the moisture content in the top soil layer are directly influenced by agricultural irrigation practices, and thus potentially allow for the quantitative estimation of IWU. In this study, we combine surface soil moisture retrievals from the spaceborne SMAP, AMSR2, and ASCAT microwave sensors with modelled soil moisture from MERRA-2 reanalysis to derive monthly IWU dynamics over the contiguous United States (CONUS) for the period 2013–2016. The methodology is driven by the assumption that the hydrology formulation of the MERRA-2 model does not account for irrigation, while the remotely sensed soil moisture retrievals do contain an irrigation signal. For many CONUS irrigation hot spots, the estimated spatial irrigation patterns show good agreement with a reference data set on irrigated areas. Moreover, in intensively irrigated areas, the temporal dynamics of observed IWU is meaningful with respect to ancillary data on local irrigation practices. State-aggregated mean IWU volumes derived from the combination of SMAP and MERRA-2 soil moisture show a good correlation with statistically reported state-level irrigation water withdrawals but systematically underestimate them. We argue that this discrepancy can be mainly attributed to the coarse spatial resolution of the employed satellite soil moisture retrievals, which fails to resolve local irrigation practices. Consequently, higher resolution soil moisture data are needed to further enhance the accuracy of IWU mapping.

scholarly journals Seasonal Nitrogen Partitioning and Nitrogen Uptake of Carrots as Affected by Nitrogen Application in a Mineral and an Organic Soil

HortScience ◽  
2006 ◽  
Vol 41 (5) ◽  
pp. 1332-1338 ◽  
Author(s):  
Sean M. Westerveld ◽  
Alan W. McKeown ◽  
Mary Ruth McDonald
Keyword(s):  
N Uptake ◽  
Mineral Soil ◽  
Growing Season ◽  
Organic Soil ◽  
Nitrogen Partitioning ◽  
N Budget ◽  
N Application ◽  
Total N ◽  
Application Rates ◽  
N Removal

An understanding of nitrogen (N) uptake and the partitioning of N during the season by the carrot crop (Daucus carota subsp. sativus [Hoffm.] Arkang.) is required to develop more efficient N fertilization practices. Experiments were conducted on both organic and mineral soils to track the accumulation of dry matter (DM) and N over the growing season and to develop an N budget of the crop. Treatments included two carrot cultivars (`Idaho' and `Fontana') and 5 N rates ranging from 0% to 200% of the provincial recommendations in Ontario. Foliage and root samples were collected biweekly from selected treatments during the growing season and assessed for total N concentration. Harvest samples were used to calculate N uptake, N in debris, and net N removal values. Accumulation of DM and N in the roots was low until 50 to 60 days after seeding (DAS) and then increased linearly until harvest for all 3 years regardless of the soil type, cultivar, and N rate. Foliage dry weight and N accumulation were more significant by 50 to 60 DAS, increased linearly between 50 and 100 DAS, and reached a maximum or declined slightly beyond 100 DAS in most cases. The N application rates required to maximize yield on mineral soil resulted in a net loss of N from the system, except when sufficient N was available from the soil to produce optimal yield. On organic soil, a net removal of N occurred at all N application rates in all years. Carrots could be used as an N catch crop to reduce N losses in a vegetable rotation in conditions of high soil residual N, thereby improving the N use efficiency (NUE) of the crop rotation.

scholarly journals Estimating irrigation water use over the contiguous United States by combining satellite and reanalysis soil moisture data

2019 ◽  
Vol 23 (2) ◽  
pp. 897-923 ◽  
Author(s):  
Felix Zaussinger ◽  
Wouter Dorigo ◽  
Alexander Gruber ◽  
Angelica Tarpanelli ◽  
Paolo Filippucci ◽  
...  
Keyword(s):  
Water Management ◽  
United States ◽  
Soil Moisture ◽  
Water Use ◽  
Irrigation Water ◽  
Soil Layer ◽  
Data Set ◽  
Soil Moisture Data ◽  
Irrigation Water Use ◽  
Irrigation Practices

Abstract. Effective agricultural water management requires accurate and timely information on the availability and use of irrigation water. However, most existing information on irrigation water use (IWU) lacks the objectivity and spatiotemporal representativeness needed for operational water management and meaningful characterization of land–climate interactions. Although optical remote sensing has been used to map the area affected by irrigation, it does not physically allow for the estimation of the actual amount of irrigation water applied. On the other hand, microwave observations of the moisture content in the top soil layer are directly influenced by agricultural irrigation practices and thus potentially allow for the quantitative estimation of IWU. In this study, we combine surface soil moisture (SM) retrievals from the spaceborne SMAP, AMSR2 and ASCAT microwave sensors with modeled soil moisture from MERRA-2 reanalysis to derive monthly IWU dynamics over the contiguous United States (CONUS) for the period 2013–2016. The methodology is driven by the assumption that the hydrology formulation of the MERRA-2 model does not account for irrigation, while the remotely sensed soil moisture retrievals do contain an irrigation signal. For many CONUS irrigation hot spots, the estimated spatial irrigation patterns show good agreement with a reference data set on irrigated areas. Moreover, in intensively irrigated areas, the temporal dynamics of observed IWU is meaningful with respect to ancillary data on local irrigation practices. State-aggregated mean IWU volumes derived from the combination of SMAP and MERRA-2 soil moisture show a good correlation with statistically reported state-level irrigation water withdrawals (IWW) but systematically underestimate them. We argue that this discrepancy can be mainly attributed to the coarse spatial resolution of the employed satellite soil moisture retrievals, which fails to resolve local irrigation practices. Consequently, higher-resolution soil moisture data are needed to further enhance the accuracy of IWU mapping.

scholarly journals 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

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.

NO3- uptake and C exudation – do plant roots stimulate or inhibit denitrification?

2020 ◽  
Author(s):  
Pauline Sophie Rummel ◽  
Reinhard Well ◽  
Birgit Pfeiffer ◽  
Klaus Dittert ◽  
Sebastian Floßmann ◽  
...  
Keyword(s):  
Soil Moisture ◽  
N Uptake ◽  
Root Exudation ◽  
Soil Surface ◽  
N Fertilization ◽  
Plant N Uptake ◽  
Mineral N ◽  
Double Labeling ◽  
Total N ◽  
Organic C

&lt;p&gt;Growing plants affect soil moisture, mineral N and organic C (C&lt;sub&gt;org&lt;/sub&gt;) availability in soil and may thus play an important role in regulating denitrification. The availability of the main substrates for denitrification (C&lt;sub&gt;org&lt;/sub&gt; and NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt;) is controlled by root activity and higher denitrification activity in rhizosphere soils has been reported. We hypothesized that (I) plant N uptake governs NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt; availability for denitrification leading to increased N&lt;sub&gt;2&lt;/sub&gt;O and N&lt;sub&gt;2&lt;/sub&gt; emissions, when plant N uptake is low due to smaller root system or root senescence. (II) Denitrification is stimulated by higher C&lt;sub&gt;org&lt;/sub&gt; availability from root exudation or decaying roots increasing total gaseous N emissions while decreasing their N&lt;sub&gt;2&lt;/sub&gt;O/(N&lt;sub&gt;2&lt;/sub&gt;O+N&lt;sub&gt;2&lt;/sub&gt;) ratios.&lt;/p&gt;&lt;p&gt;We tested these assumptions in a double labeling pot experiment with maize (Zea mays L.) grown under three N fertilization levels S / M / L (no / moderate / high N fertilization) and with cup plant (Silphium perfoliatum L., moderate N fertilization). After 6 weeks, all plants were labeled with 0.1 g N kg&lt;sup&gt;-1&lt;/sup&gt; (Ca(&lt;sup&gt;15&lt;/sup&gt;NO&lt;sub&gt;3&lt;/sub&gt;)&lt;sub&gt;2&lt;/sub&gt;, 60 at%), and the &lt;sup&gt;15&lt;/sup&gt;N tracer method was applied to estimate plant N uptake, N&lt;sub&gt;2&lt;/sub&gt;O and N&lt;sub&gt;2&lt;/sub&gt; emissions. To link denitrification with available C in the rhizosphere, &lt;sup&gt;13&lt;/sup&gt;CO&lt;sub&gt;2&lt;/sub&gt; pulse labeling (5 g Na&lt;sub&gt;2&lt;/sub&gt;&lt;sup&gt;13&lt;/sup&gt;CO&lt;sub&gt;3&lt;/sub&gt;, 99 at%) was used to trace C translocation from shoots to roots and its release by roots into the soil. CO&lt;sub&gt;2&lt;/sub&gt; evolving from soil was trapped in NaOH for &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C analyses, and gas samples were taken for analysis of N&lt;sub&gt;2&lt;/sub&gt;O and N&lt;sub&gt;2&lt;/sub&gt; from the headspace above the soil surface every 12 h.&lt;/p&gt;&lt;p&gt;Although pots were irrigated, changing soil moisture through differences in plant water uptake was the main factor controlling daily N&lt;sub&gt;2&lt;/sub&gt;O+N&lt;sub&gt;2&lt;/sub&gt; fluxes, cumulative N emissions, and N&lt;sub&gt;2&lt;/sub&gt;O production pathways. In addition, total N&lt;sub&gt;2&lt;/sub&gt;O+N&lt;sub&gt;2&lt;/sub&gt; emissions were negatively correlated with plant N uptake and positively with soil N concentrations. Recently assimilated C released by roots (&lt;sup&gt;13&lt;/sup&gt;C) was positively correlated with root dry matter, but we could not detect any relationship with cumulative N emissions. We anticipate that higher C&lt;sub&gt;org&lt;/sub&gt; availability in pots with large root systems did not lead to higher denitrification rates as NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt; was limited due to plant uptake. In conclusion, plant growth controlled water and NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt; uptake and, subsequently, formation of anaerobic hotspots for denitrification.&lt;/p&gt;

REGRESSIONS FOR ESTIMATING STRAW YIELDS AND N AND P CONTENTS OF SPRING WHEAT AND N MINERALIZATION IN A BROWN LOAM SOIL

1988 ◽  
Vol 68 (2) ◽  
pp. 337-344 ◽  
Author(s):  
C. A. CAMPBELL ◽  
R. P. ZENTNER ◽  
F. SELLES
Keyword(s):  
Soil Moisture ◽  
Moisture Content ◽  
Spring Wheat ◽  
N Mineralization ◽  
Soil Moisture Content ◽  
N Uptake ◽  
Growing Season ◽  
Net N Mineralization ◽  
Loam Soil ◽  
Growing Season Precipitation

Data from an 18-yr crop rotation study carried out on a Brown loam soil at Swift Current, Saskatchewan, were used to estimate equations that relate spring wheat straw yields, and N and P content of grain and straw to moisture use (MU). Moisture use was defined as soil moisture content in 0- to 120-cm depth at seeding, less soil moisture content at harvest, plus growing season precipitation. Grain yields were also related to straw yields and to N content of the straw. Potential net N mineralization (Nmin) in summerfallow (periods during the growing season with negative Nmin omitted) was related (r = 0.74**) to precipitation received during the spring to fall period. An attempt to relate apparent net Nmin (determined by N balance) in cropped systems to growing season precipitation or to MU was not successful. Highly significant linear regressions were obtained for straw yields, grain N and P contents vs. MU, and for grain yield vs. straw yield (r = 0.66** – 0.83**), but the other relationships were less reliable (r = 0.41** – 0.55**) though still significant. We discussed how these relationships might be used to estimate fertilizer N requirements, for examining N immobilization-mineralization, and for estimating residue sufficiency for erosion control on summerfallowed land. Key words: Straw:grain ratio, N uptake, P uptake, crop residues, N mineralization

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