Increased nitrogen use efficiencies as a key mitigation alternative to reduce nitrate leaching in north china plain

agricultural water management 89 (2007) 137–147

available at www.sciencedirect.com

journal homepage: www.elsevier.com/locate/agwat

Increased nitrogen use efficiencies as a key mitigation alternative to reduce nitrate leaching in north china plain Xiaoxin Li a,b,d, Chunsheng Hu a,*, Jorge A. Delgado c, Yuming Zhang a, Zhiyun Ouyang b a

Center for Agricultural Resources Research, Institute of Genetic and Developmental Biology, Chinese Academy of Science (CAS), Shijiazhuang 050021, China b Research Center for Eco-Environmental Sciences, CAS, Beijing 100085, China c USDA-ARS, Soil Plant Nutrient Research Unit, Fort Collins, CO, USA d Graduate School CAS, Beijing 10003, China

article info

abstract

Article history:

The Northern China Plain (NCP) produces over 20% of the national grain production. Best

Accepted 14 December 2006

management practices (BMP) for intensive irrigated cropping systems of the NCP are

Published on line 2 February 2007

based on large nitrogen (N) applications without accounting for N budgets. There are concerns that non-scientific based BMPs may be impacting underground water resources.

Keywords:

We conducted the first study in this region, located at the Luancheng Experimental

Best management practices

Research Station that measured the effects of N fertilizer rates on nitrate-nitrogen

Lysimeter

(NO3-N) leaching losses. From October 1, 2001 to September 30, 2004, we used a water

Nitrogen use efficiencies

balance approach with a neutron probe, weighing lysimeter, and suction cups located at

Nitrate leaching

1.8 m depths on a winter wheat (Triticum aestivum L.)–corn (Zea mays L.) rotation to monitor

Water balance

NO3-N leaching. Residual soil NO3-N, yields, and N uptake by aboveground biomass were

North China Plain

also measured. Corn received two surface broadcast applications every year of 50, 100, 150 and 200 kg urea-N ha1 for the N200, N400, N600, and N800 treatments, respectively. The first broadcast application was at seeding and the second at tassel. Similarly, winter wheat received two surface broadcast applications, initially as a pre-plant and a second application at the jointing stage of growth in spring. We monitored NO3-N leaching losses for the N200, N400, and N800 treatments. Average NO3-N leaching losses during wheat–corn season were 6, 58, and 149 kg NO3-N ha1 year1 for the 200, 400, and 800 kg N ha1 year1 treatments, respectively. The NO3-N leaching increased with N applications (P < 0.05) and were in agreement with the NO3-N concentrations of 12, 74, and 223 mg NO3-N L1 for soil water at 1.8 m depths for the 200, 400, and 800 kg N ha1 year1 treatments, respectively. Higher than needed N fertilizer applications increased the NO3-N leaching losses and reduced the N use efficiency (NUE) without yield increases. We propose that there is a need for a new scientifically based BMP approach for the NCP based on N budgets that credits soil NO3-N before planting, N mineralization from soil organic matter, and other potential N sources as a key mitigation alternative to increase NUE and reduce NO3-N leaching in this region. # 2007 Elsevier B.V. All rights reserved.

* Corresponding author. Tel.: +86 311 85814360; fax: +86 311 85814360. E-mail address: [email protected] (C. Hu). 0378-3774/$ – see front matter # 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.agwat.2006.12.012

138 1.

agricultural water management 89 (2007) 137–147

Introduction

Nitrogen is one essential, key nutrient needed to increase and maintain worldwide agricultural production. However, it has been reported that over-application can contribute to environmental impacts in China and in other worldwide regions (Newbould, 1989; Follett, 1989; Zhang et al., 1996; Delgado, 2002). Land management practices can affect the N fate and availability of NO3-N, increasing leaching in the main pathways that impact groundwater quality (Davies and SylvesterBradley, 1995; Fedkiw, 1991; Follett and Delgado, 2002; Follett et al., 1991; Hall et al., 2001; Hallberg, 1989; Juergens-Gschwind, 1989; Milburn et al., 1990; Schroder, 1985; Spalding and Exner, 1993). For some regions, tile drainage will be the main mechanism of off-site transport of NO3-N (Randall and Goss, 2001; Randall and Iragavarapu, 1995; Randall et al., 1997). For other regions, over-irrigation or high precipitation events on slope landscapes will be a main pathway for off-site transport of N with surface runoff to water bodies, especially for soils with low permeability (Bjorneberg et al., 2002; Eghball et al., 2002; Khaleel et al., 1980). NO3-N transport and leaching in tiles and/or N transport in surface runoff can impact water bodies. Best management practices that synchronize N uptake with N availability can increase NUE and minimize these N losses to the environment (Diez and Roman, 1997; Delgado, 1998, 2001; Hergert, 1986; Shaffer and Delgado, 2002; Smika et al., 1977). Using deeper rooted rotations and BMPs can contribute to reduce NO3-N leaching and even recover NO3-N from groundwater (Delgado, 1998, 2001). Other management practices that have been reported to reduce NO3-N leaching and/or increase NUE across spatial variability is the management of N inputs based on management zones (Khosla et al., 2002; Delgado et al., 2005). Using controlled release fertilizer types (Shoji and Gandeza, 1992; Amans and Slangen, 1994; Rauch and Murakami, 1994; Delgado and Mosier, 1996; Shoji et al., 2001); splitting N recommendations into several applications (Gunasena and Harris, 1968; Russelle et al., 1981; Westermann and Kleinkopf, 1985); using field tests, such as the pre-sidedress soil nitrate test (PSNT; Bundy and Meisinger, 1994); remote sensing (Bausch and Delgado, 2003; Delgado and Bausch, 2005) can all contribute to accurately applying the N application in relation to the crop’s N uptake, reducing the potential for N losses. New tools, such as modeling (Delgado et al., 2000, 2001; Shaffer, 2002; Rimski-Korsakov et al., 2004) and a new N index (Delgado et al., 2006), can contribute to assess N budgets and effects of BMPs on cropping system’s N use efficiencies (CSNUE). Meisinger and Delgado (2002) reported on the principles to manage N that can reduce NO3-N leaching. Several organizations have set NO3-N concentration limits for drinkable water. The World Health Organization and the European Community decided that water contains levels higher than 11.3 mg NO3-N L1 is undrinkable (Council of European Communities, 1998), while the U.S. Environmental Protection Agency (1989) and the Health Canada (the Health Canada, 1996; Basso and Ritchie, 2005; Li and Li, 2005) set the limit at 10.0 mg NO3-N L1. The predominant cropping system in the Northern China Plain (NCP) is a winter wheat (Triticum aestivum L.)–corn (Zea mays L.) rotation. The NCP produces over 20% of the national

grain production, which makes this one of the key agricultural regions for a country with a population of 1.2 billion. This rotation is called an intensive rotation, since both crops are grown within a year without a fallow period and generally under flood irrigation with pumped groundwater and high N inputs. Liu and Ju (2003) reported that N fertilizer rates for this region averaged 450 kg N ha1 year1. Zhu and Chen (2002) reported N fertilizer rates as high as 400–600 kg N ha1 year1 or even 600–900 kg N ha1 year1. However, N applications can be as high as 1000–1500 kg N ha1 year1 for greenhouse vegetables (Zhu and Chen, 2002). Zhang et al. (1996) reported that out of 69 wells surveyed across 14 counties from the NCP, over 50% had nitrate N concentrations above 10 mg NO3-N L1. The impact on shallow groundwater in the NCP has also been reported by Zhu and Chen (2002). The combination of excessive N fertilizer rates (Liu and Ju, 2003) and improper irrigation (Zhu and Zhang, 2005; Hu et al., 2005) can contribute to NO3-N leaching and potential impacts to groundwater. Additionally, overirrigation is also causing the depletion of groundwater (Zhang et al., 1995, 2003; Hu et al., 2005). Hu et al. (2005) reported the potential to cut irrigation by 50% in the NCP without reducing yields. Shaffer and Delgado (2002), Delgado (2004), Hu et al. (2005), and Delgado et al. (2006) reported that higher water use efficiency needs to be considered in an N index, since better water management will significantly contribute to lower NO3N leaching across the NCP. There is the need to assess the effects of N fertilizer rates on NO3-N leaching losses for this important region to minimize potential impacts on groundwater. Our objective was to conduct the first assessments of N fertilizer rates on NO3-N leaching for this region. Additionally, we wanted to conduct an N budget analysis to determine the potential to use an N budget approach. This will improve NUE as a mitigation alternative to reduce NO3-N leaching for the NCP.

2.

Material and methods

2.1.

Experimental site

Field experiments were conducted at Luancheng AgroEcological Experimental Station (378530 1500 N, 1148400 4700 E, elevation 50 m), Chinese Academy of Sciences (Fig. 1), which is located at the piedmont of the Taihang Mountains, in the Northern China Plain. Table 1 shows soil physical properties of the silt loam site. Agric Rusty Ustic Cambisol, as classified by Zitong (1999), is representative of the predominant soils located in this region. The soil texture, bulk density, and saturated hydraulic conductivity were measured with the methods of Day (1965), USDA-SCS (1988), and Klute (1965), respectively. Daily meteorological data of air temperature, solar radiation, wind speed, humidity, and precipitation were collected from a weather station located at the Luancheng Agro-Ecological Experimental Station, approximately 300 m from the experimental site. The mean annual precipitation at the station during the study period was 536 mm (Fig. 2), and the mean air temperature at the site was 12.3 8C, fluctuating from maximum and minimum monthly temperatures of 26.4 and 3.9 8C for July and January, respectively.

139

agricultural water management 89 (2007) 137–147

Fig. 1 – Location of the Luancheng Agro-Ecological Experimental Station of Chinese Academy of Sciences and approximate area of the North China Plain (NCP).

2.2. Crop management, experimental design and construction of lysimeter The experimental design was a completely randomized block with four N fertilizer rates (200, 400, 600, and 800 kg ureaN ha1 year1) and three replications. These rates reflect feasible inputs (below average, average, high, and very high) currently used in the NCP. Each plot was 2.5 m  2.5 m, and was bordered by concrete walls, which were positioned at 2.0 m below and 0.2 m above the soil surface to prevent lateral flow of water and nutrients. The soil in the 6.3 m2 plot area was undisturbed by outside factors, a 2.0 m wall was built around each plot for this purpose. Each plot was separated by alleys, which measured approximately 0.9 m in width. Porous ceramic suction cup samplers were selected installed to a depth of 1.8 m below the ground for the plots receiving 200, 400, and 800 kg urea-N ha1 year1. A vacuum pump was connected to the samplers via flexible polyethylene tubing.

Zhang (1999), Zhang et al. (2003) reported that the root systems of winter wheat and corn, for plots close to our area, were not observed at 1.8 m depths. Aluminum neutron access tubes, 2.0 m long, sealed at their bases, were installed at the center of the plots. It was assumed that the rooting systems of the crops were located at 1.5 m in depth, in concurrence with Zhang et al. (2003). The plots with the new 2.0 m wall and aluminum, neutron access tubes were not sampled for 3 years from year 1998, in order to leave enough time for each plot area to settle for this study. This initial lag period also helped the system to reach a relative, steady state for N inputs and residual soil NO3-N, in order to receive a respective N fertilizer input. For these 3 initial years, all plots were managed the same, except for the N fertilizer rates of 200, 400, 600, and 800 kg ureaN ha1 year1 for the N200, N400, N600, and N800 treatments, respectively, for applications as described below. For our study of the 2001–2002 winter wheat–corn rotation, the first sample was collected in October of 2001 after the harvest of

Table 1 – Soil physical characteristics of a silt loam site, Agric Rusty Ustic Cambisol Depth (cm)

0–20 20–40 40–110 110–150

Bulk density (g cc3)

Particle size (%) Sand

Silt

Clay

41.8 35.7 29.2 21.9

53.6 58.0 57.4 64.1

4.6 6.3 13.5 14.0

1.22 1.44 1.46 1.56

Saturated hydraulic conductivity (mm h1)

53.5 28.6 44.5 23.0

This silt loam site, where the nitrogen management studies were conducted, is located at the Luancheng Agro-Ecological Experimental Station at the Chinese Academy of Sciences.

140

agricultural water management 89 (2007) 137–147

and irrigation are shown in Table 2. A flow meter was used to apply the same amount of water to each plot. Winter wheat received two surface broadcast applications every year of 50, 100, 150, and 200 kg urea-N ha1 for the N200, N400, N600, and N800 treatments, respectively. The first application was a pre-plant broadcast urea-N application. For the 2001–2002 and 2002–2003 season, winter wheat plots were irrigated before planting. Fertilizer was broadcasted and incorporated after each irrigation period (Table 2). Winter wheat received a second irrigation in the fall seasons of 2001 and 2002, about 5 weeks following N fertilizer applications (Table 2). For the 2003–2004 growing season, there was no fall irrigation after the N fertilizer application. The winter wheat received a second N fertilizer application at the jointing stage of growth in spring, followed by an irrigation event. Tillage, planting, harvesting, and irrigation scheduling are shown in Table 2. Moldboard plow tillage was done before wheat planting (Table 2). Winter wheat was planted by the middle of October and harvested around the first week of June. Corn was planted the following week after harvesting wheat (Table 2). Yield was measured by hand harvesting the aboveground biomass in the 6.3 m2 plot areas (less 5 cm stubble), drying the harvest at 75 8C, threshed to separate grain and straw, and ground by compartment with a 2 mm sieve. Grain and straw N analyses were done using the Kjeldahl analysis. The yield and N uptake data from these plots were published by Hu et al. (2006).

Fig. 2 – Daily rainfall for the 2001–2002 (a), 2002–2003 (b), and 2003–2004 (c) growing seasons. Data collected at the Luancheng Agro-Ecological Experimental Station of Chinese Academy of Sciences.

2.3. Soil water profile and suction cup lysimeter measurements

corn and before the application of N fertilizer to the winter wheat. Corn received two surface broadcast applications every year of 50, 100, 150, and 200 kg urea-N ha1 for the N200, N400, N600, and N800 treatments, respectively. The first broadcast application was at seeding, and the second application was at tassel. Flood irrigation was applied immediately after each N fertilization event. The schedule of N fertilizer applications

The neutron probe was used to measure soil water content at 0.2 m intervals from 0.1 to 1.7 m. Neutron probe measurements were collected every 5 days during the growing season. However, they were collected every 10 days during winter. Additional neutron probe measurements were conducted after significant rainfall and before irrigation as needed. A portable vacuum pump was used to apply 80 kPa for 24 h to collect soil water samples from suction cups every 2 weeks. During winter, no samples were collected when

Table 2 – Schedules for tillage, planting, irrigation (mm of water applied in parenthesis), and urea-nitrogen (N) fertilizer for the first (N first) and second (N second) applications MN

Growing season WW

Tillage Planting

10/10/01 10/12/01

Irrigation

N first N second Harvest

CORN

WW

CORN

WW

6/15/02

10/16/02 10/16/02

6/15/03

10/6/01 (93) 11/30/01 (70) 3/15/02 (70) 4/25/02 (70) 5/30/02 (70)

6/16/02 (116) 7/17/02 (116) 8/20/02 (93)

10/7/02 (93) 11/16/02 (70) 4/12/03 (70)

6/23/03 (70) 7/15/03 (70) 8/14/03 (47)

3/22/04 (93) 5/12/04 (70)

6/21/04 (47) 7/22/04 (35) 8/11/04 (70) 9/9/04 (47) 9/9/04 (47)

10/10/01 3/15/02 6/8/02

6/16/02 7/17/02 9/28/02

10/16/02 4/12/03 6/10/03

7/15/03 8/14/03 10/2/03

10/14/03 3/22/04 6/8/04

7/22/04 8/11/04 9/29/04

The harvest dates of winter wheat (WW) and corn are also listed. Value in italic signifies the amount of water applied (mm).

10/14/03 10/14/03

CORN 6/18/04

agricultural water management 89 (2007) 137–147

141

lysimeter, was measured by the difference method on an average of every 5 days, during the entire length of our study. For details of procedures, see Hu et al. (2005). Since there was only one lysimeter, the AET was only conducted for the farmers’ traditional winter wheat–corn management practices, with 360 mm of irrigation applied in four irrigation events. The N fertilizer inputs for corn were 100 kg ureaN ha1, broadcasted at seeding, and a second 100 kg ureaN ha1 was broadcasted at tassel. For winter wheat, there was an initial 100 kg urea-N ha1 pre-plant broadcast urea-N application and a second 100 kg urea-N ha1 broadcasted at the jointing stage of growth in spring.

2.5.

Fig. 3 – Soil NO3-N concentrations by depth collected after harvest of corn (October) on a winter wheat–corn crop rotation. The N rate treatments received 200 (N200), 400 (N400), 600 (N600), and 800 (N800) kg urea-N haS1 yearS1.

temperatures dropped below zero. The soil solution was analyzed for NO3-N and NH4+-N with a colorimetric analysis conducted by an automated Technicon8 flow injection analysis. We only presented the NO3-N results, since the NH4+-N concentrations were minimal (Fig. 3) (Braun-Luebbe Analyzing Technologies Inc., 19871). In October, before planting wheat, soil samples were collected from each plot in 0.2 m increments, to a depth of 1.8 m, using a hand auger. The samples were sub-sampled for water content by drying them at 105 8C. The other subsample was sieved through a 2 mm sieve, and two extractions were conducted by weighing 10 g of soil, extracted with 50 mL of 1N KCl by shaking samples for 1 h and then filtering. The extracts were analyzed for NO3-N and NH4+-N as described above. Results were corrected by the percentage of water content.

2.4.

Meteorological measurements

Actual evapotranspiration (AET) was obtained from a 3 m2 weighing lysimeter, with a depth of 2.5 m, located at approximately 100 m from our site. The mechanical scale used can provide a resolution of 0.02 mm of water loss. The 24 h change in water content, located in the weighing

1

Names are necessarily to report factually on available data; however, neither the USDA nor the Chinese Academy of Sciences guarantees or warrants the standard of the product, and use of the product by the USDA or Chinese Academy of Sciences implies no approval of the product to the exclusion of others that may be suitable.

Determination of water balance and nitrate leaching

Soil water balance was calculated on a daily time step according to the procedures from Moreno et al. (1996), using daily change of water storage from zero to depth z, considering daily rainfall, irrigation, upwards water flow through capillaries, runoff, actual evapotranspiration, and drainage (Eq. (1)). Since there was no runoff at our site and U was estimated to be minimal, we solved equation one for drainage (Eq. (2)). DSWðzÞ ¼ P þ I þ U  R  AET  DðzÞ

(1)

where DSW(z) is the daily change of water storage from zero to depth z (mm), P the daily rainfall (mm), I the irrigation (mm), U the upward water flow through capillary (mm), R the runoff (mm), AET the actual evapotranspiration (mm) and D(z) is the drainage (mm) of the depth below the effective root zone. DðzÞ ¼ P þ I þ DSWðzÞ  AET

(2)

The NO3-N that leached (Nleach) below the root zone, was obtained by multiplying drainage D(z) by the measured NO3-N concentrations with the suction cups located at 1.8 m depth (Eq. (3)). The suction cup NO3-N concentrations were used for any deep drainage that occurred during the 2 week period. Nleach ¼

X

DðzÞi  Ci

(3)

Statistical analyses were conducted with the variance of (P < 0.05) (Dowdy and Wearden, 1991). To assess the potential to improve nitrogen management practices, we used average N budgets similar to Delgado (2001), and therefore calculated the cropping system’s N use efficiencies (CSNUE) as a key mitigation alternative to reduce NO3-N leaching (Eq. (4)). CSNUE ¼

Ncont  100 Nfert þ Nsi þ Nir þ Nmin þ Natm

(4)

where CSNUE is the cropping system N use efficiency (%), Ncont the N content at harvest (kg N ha1), Nfert the N applied as fertilizer (kg N ha1), Nsi the root zone inorganic N (kg NH4N + NO3-N ha1) before planting (kg N ha1), Nir the N applied in irrigation water (kg N ha1) [average 8 kg N ha1], Nmin the soil organic matter N mineralization during growing season (kg N ha1) [45 kg N ha1 per 1% soil organic matter; Vigil et al., 2002] and Natm is the atmospheric N deposition (kg N ha1) [31 kg N ha1; Liu et al., 2006].

142

agricultural water management 89 (2007) 137–147

3.

Results and discussion

3.1.

Soil properties

Table 3 – Monthly measured evapotranspiration (mm), measured with a weighing lysimeter, for the wheat–corn 2001–2002, 2002–2003, and 2003–2004 growing seasons Month

The soil physical properties are described in Table 1 for this fine silt loam site. The content of fine particles (silt and clay) increases with depth. The surface at 0.2 m depth had 53.6 and 4.6% of silt and clay, which is, respectively, lower than the 64.1 and 14% silt and clay measurements for the 1.1–1.5 m depth soil horizon. Similarly, bulk densities also increases with depth from 1.22 g cm3 in the surface 0.2 m to 1.56 g cm3 for the 1.1–1.5 m depth soil horizon. The soil hydraulic conductivity of 53.5 mm h1 for the surface 0.2 m horizon decreases with depth to 23 mm h1 for the lower horizon (Table 1).

3.2.

Water balance and calculated drainage losses

Corn received 325, 187, and 203 mm of irrigation for the 2002, 2003, and 2004 growing seasons, respectively (Table 2). Winter wheat received a total of 373, 233, and 163 mm of irrigation during the 2001–2002, 2002–2003, and 2003–2004 growing seasons, respectively (Table 2). The monthly AET ranged from 10 to 187, 11 to 196, and 7 to 179 mm during the 2001–2002, 2002– 2003, and 2003–2004 growing seasons, respectively (Table 3). For the 2001–2002 growing season, the total precipitation and irrigation was 382 and 698 mm, respectively. This was an additional 84 mm of water inputs than the total 996 mm AET (Tables 2 and 3 and Fig. 2). For the 2002–2003 growing season, the total precipitation and irrigation was 476 and 420 mm, respectively. This was 36 mm lower than the estimated 932 mm for AET. Even if the total precipitation events were

Year

y

October November December January February March April May Junez July August September§ y z §

2001–2002

2002–2003

40 30 10 11 18 75 144 175 93 130 187 85

33 22 11 11 13 30 165 196 55 109 179 107

2003–2004 43 30 17 7 17 60 155 179 61 128 144 100

Wheat is planted. Wheat is harvested, followed by planting corn. Corn is harvested.

lower than the total AET, there were still water leaching events (Fig. 4). This clearly shows that water leaching for these intensively managed NCP cropping systems is event based. Our data shows that we need to assess the water budgets with intensive measurements (e.g. neutron probe, weighing lysimeter, and suction cups) to be able to monitor water drainage losses out of the root zone. For the 2003–2004 growing season, the total precipitation and irrigation was 611 and 409 mm, respectively. This was 79 mm higher than the estimated 941 mm for AET.

Fig. 4 – Calculated drainage at 1.8 m depths for treatments receiving total annual N fertilizer rates of 200 (N200), 400 (N400), and 800 (N800) kg urea-N haS1 yearS1. Drainage calculated for the for the 2001–2002 (a), 2002–2003 (b), and 2003–2004 (c) growing seasons.

agricultural water management 89 (2007) 137–147

Our results are different from Zhang et al. (2005) and Sun et al. (1993), who only reported drainage events for the corn growing period. We found that water leaching events can occur in both of the winter wheat and corn growing systems, and these leaching events are driven by high irrigation and precipitation events (Fig. 4). These leaching events occur predominantly during April, August, and October. The August and October drainage events correlate with the higher precipitation events, which is approximately 70% of the total annual rainfall from July to September (Fig. 2). This also correlates with the larger irrigation events during October, a month with low AET. The spring leaching events during the winter wheat growing season correlates with the low AET for March, combined with the high irrigation events of March and April (Table 2 and Fig. 4).

3.3.

Soil NO3-N

The initial and final residual total soil NO3-N was significantly different, due to treatments and increased with N applications. After the lysimiters were built, the plots were managed similarly, however they not sampled for leaching for 3 years to provide enough time for each plot area to settle. During these 3 years all management practices were the same, except for the N fertilizer inputs for the N200, N400, N600, and N800 treatments. The initial soil sample collected in October 2001, after 3 years of stabilization for each treatment, had 66(a), 196(b), 431(bc), and 618(cd) kg NO3-N ha1 for the N200, N400, N600, and N800 treatments, respectively (numbers with different letters significantly different at P < 0.05). The final residual soil NO3-N, after 6 years of N fertilizer applications (October 2004), had 94(a), 406(b), 411(b), and 500(b) kg NO3-N ha1 for the N200, N400, N600, and N800 treatments, respectively. Similar results were observed and reported that small grain commercial farming operations in South Central Colorado with similar BMPs had lower residual soil NO3-N of about 30 kg NO3-N ha1 for top 0.9 m (Delgado, 2001). High N rate input commercial vegetable crops with shallower rooted systems with similar BMPs had higher residual soil NO3-N of about 100 kg NO3-N ha1 for top 0.9 m. It means that NO3-N was lost, particularly in high N fertilizer rates after the 3 year experimental period (2001–2004), compared with the initial NO3-N obtained with respect to the treatments of N applications in a wheat–corn rotation system.

3.4.

Yields, N uptake, N use efficiencies and N balance

Hu et al. (2006) reported that there were no significant differences due to N fertilizer rates on winter wheat or corn grain yields and aboveground biomass or N uptake. We used the average N uptake and grain yields reported by Hu et al. (2006). The total grain yield production of the wheat–corn rotation system was 9971 kg ha1 year1 with an N uptake content of 188 kg N ha1 year1 under the treatment of N200. The total grain N uptake recovery averaged less than 200 kg N ha1 year1 for the N200, N400, N600, and N800 treatments, respectively. The total percentage of annual grain N recovery for the N200, N400, N600, and N800 treatments was 94, 47, 31, and 24%, respectively (total annual grain N recovery percentage = (annual total N content grain/annual N fertilizer

143

applied  100)). There is a significant reduction in N recovery in the grain for the excessive N applications above 200 kg N ha1 year1, without any increase in yield. The total aboveground biomass production (grain, stalks, and leaves) of winter wheat and corn was 21903 kg ha1 year1, with an N uptake content of 277 kg N ha1 year1. The CSNUE for the N200, N400, N600, and N800 treatments was 75, 40, 24, and 18%, respectively. There is a significant reduction in CSNUE by the intensive grain rotation, due to excessive N applications above 200 kg N ha1 year1, without any increase in yield. The total N uptake of 277 kg N ha1 year1 of the N200 with the lower residual soil NO3-N ha1 supports the hypothesis that soil organic matter mineralization and atmospheric deposition contributes to supplies additional N uptake by the crops. These results agree with recent studies from Liu et al. (2006) that reported a total average annual atmospheric deposition of 31 kg N ha1 year1 for this region. The soil organic matter for these plots was 1.4%, and we estimate that there is an N cycling of 63 kg N ha1 using the reported 45 kg N ha1 by Vigil et al. (2002) for the USA. NO3-N in the irrigation water was at the rate of 8 kg N ha1. With these previous assumptions, the total N input for the N200 will be 368 kg N ha1 year1 (200 kg N fertilizer, 31 kg N atmospheric deposition, and 63 kg N from soil organic mater; initial soil inorganic 66 kg NO3-N ha1 plus 8 kg N ha1 background in irrigation water). This N balance suggests that 200 kg N ha1 will supply the N needed to maximize yields and NUE. We recommend that initially, new soil testing programs be implemented in the region. The rate should be based on the expected dry grain yield production (31 kg N per every 1000 kg of wheat dry grain and 27 kg N per every 1000 kg of corn dry grain). The recommended N fertilizer rate based on yield could be adjusted by crediting the initial soil NO3-N from the top 0– 0.6 m surface horizon. We recommend that 50% of the NO3-N added with the irrigation water should be credited. Potential mineralization from the soil organic matter should be credited at a conservative 30 kg N ha1 year1 per 1% of soil organic matter (30% credit for the winter wheat growing season and 70% credit for corn). Using this formula and recommendations, the expected N rates applied to N200, N400, N600, and N800 treatments during the 2001 growing season would had been 218, 90, 0, and 79 kg N ha1, respectively. Since there was no response to N fertilizer rates above 200 kg N ha1, the expected grain NUE would had been increased to 97, 221, NA (no N fertilizer applied to N600) and 250% for the N200, N400, N600, and N800 treatments, respectively. The estimated NUE from our new formula and recommendations agrees with the observed no yield response to N fertilizer rates greater than 200 kg N ha1. Using our formula and assumptions we calculated the need of an N fertilizer application of 218 kg N ha1, for the N200 treatment. This rate is similar to the observed response for maximum yield to 200 kg N ha1. We estimated that there was a need to applied 90, and 79 kg N ha1, for the N400, and N800 treatments. Since the roots from wheat and corn grow as deep as 1.5 m and we our formula and recommendations just account for N content in the 0–0.6 m soil layer, we assume that wheat and corn are capable of scavenging N from 0.6 to 1.5 m depths that are not accounted by our formula and recommendations. Even if the

144

agricultural water management 89 (2007) 137–147

crops can scavenge N from these lower depths, we recommend that the soil sample procedures should account only for the NO3-N in the surface 0–0.6 m soil layer since with our conservative method the NUE would be significantly increased reducing potential N losses to the environment in the NCP. We recommend additional studies to improve BMPs that contribute to water quality. Studies on the effects of soil type, soil texture, crop varieties, spatial variability should be conducted. BMPs, such as improved irrigation and credit of N from crop residue, green cover crops, and manures should also be studied. We also recommend the test of new tools such as modeling to help monitor BMPs for the NCP. The development of a regional N index with site specific information for the NCP, similar to the one developed by Delgado et al. (2006), can also be a tool to help improve BMPs in the region. There were no significant N uptake differences (see Hu et al., 2006) other than additions of N higher than N200 contributing to increase N losses to the environment and NO3N leaching losses. The response in residual soil NO3-N was monitored over this long period of 3 years. This study clearly shows that NCPs higher than needed N inputs, such as N400 N600, and N800, will significantly increase the NO3-N available to leach, especially since the N uptakes have not been increased significantly for the additional 200, 400, and 600 kg N ha1 inputs of N for the N400, N600, and N800 treatments. Another alternative for this region is to develop an N index based on N balances, such as the one developed by Delgado et al. (2006). The Delgado et al. (2006) N index, although qualitative in rankings, is based on quantitative N balances and could be a potential tool to assess the potential N looses and CSNUE (Delgado et al., 2006).

3.5.

Nitrate leaching losses

Our data clearly shows that the NO3-N in the 1.8 m profile increases significantly with excessive N fertilizer rates (Fig. 5; P < 0.05), agree with Hu et al. (2001). Soil water concentrations, due to higher N fertilizer rates, were higher for the N800 than for the N400 and N200 treatments (P < 0.05). This clearly shows that for these systems representative of the NCP, higher N inputs can increase the potential for NO3-N leaching. The average NO3-N leaching during the three growing seasons was 6, 58, and 150 kg NO3-N ha1 for the N200, N400, and N800 treatments (Table 4), respectively. This is equivalent to a NO3-N leaching coefficient loss of 3, 15, and 19% of the total N fertilizer applied for the N200, N400, and N800 treatments, respectively. The NO3-N leaching increased with excessive N fertilizer applications (P < 0.05) and were in agreement with

Fig. 5 – Soil water NO3-N concentrations sampled with suction cups at 1.8 m depths for treatments receiving total annual N fertilizer rates of 200 (N200), 400 (N400), and 800 (N800) kg urea-N haS1 yearS1.

the 12, 74, and 223 mg NO3-N L1 average soil water concentrations below the root zone at 1.8 m depths for the 200, 400, and 800 kg N ha1 year1 treatments, respectively. Our results are in agreement with Zhang et al. (2005), and therefore used suction cups to measure NO3-N leaching for the winter wheat–corn rotations on a similar silt loam site. They found NO3-N leaching at a rate of 12 and 61 kg NO3-N ha1 for a 2 year study. Their 37 kg NO3-N ha1 leaching average for an N fertilizer rate of 412 kg N ha1 and average irrigation of 469 mm is in agreement with our average measurement for the N400 treatment of 58 kg NO3-N ha1 leaching and 38–90 kg NO3-N ha1 leaching range. Annual NO3-N ha1 leaching losses were relatively constant for the N200 and N800 treatments. N200 NO3-N ha1 leaching losses were 2, 6, and 11 kg NO3-N for the first, second, and third growing seasons, respectively. These losses were

Table 4 – Total water drainage and nitrate (NO3-N) leaching losses from a 1.8 m depth during the wheat–corn growing seasons Water drainage (mm year1)

Growing season

2001–2002 2002–2003 2003–2004

Leached NO3-N (kg NO3-N ha1 year1)

N200

N400

N800

N200

N400

71  7 62  15 61  21

47  12 73  5 80  14

61  43 62  10 59  9

21 65 11  5

38  5 46  17 90  36

N800 160  49 144  64 145  71

This shows the total water and NO3-N leaching losses for the plots receiving 200 (N200), 400 (N400), and 800 (N800) kg urea-N ha1 year1.

agricultural water management 89 (2007) 137–147

significantly lower than the 160, 144, and 145 kg NO3N ha1 year1 measured for the N800 treatments for the first, second, and third growing seasons, respectively (P < 0.05). The N400 annual, average NO3-N ha1 leaching losses of 38, 46, and 90 were more varied from year to year.

4.

Conclusions

Our study is the first to use suction cups to assess NO3-N leaching under different N rates for the NCP. Our soil profile data, soil water NO3-N concentrations at 1.8 m depths collected with suction cups, and our water balance to calculate drainage and NO3-N leaching losses are all correlated. This shows that excessive N fertilizer rates will contribute to accumulate large amounts of NO3-N in the soil profile, to over 1400 kg NO3-N ha1 on the top 1.5 m. Additionally, excessive N fertilizer rates will contribute to large N losses to the environment, with NO3-N leaching losses of up to 150 kg NO3-N ha1 year1. There is the need for a program to be established to help farmers use an N balance approach based on N from mineralization of organic matter initial soil NO3-N as well as N fertilizer inputs to reduce the NO3-N leaching losses that are impacting underground water resources across the NCP. Additionally, if we cut the N inputs, the pathways for other N losses will also be reduced (Delgado, 2002). There is also the need to test new tools such as the Delgado et al. (2006) N index, based on the framework presented by Shaffer and Delgado (2002) or modeling to assess the N management across the NCP region. The principles for managing NO3-N leaching, as reported by Meisinger and Delgado (2002), need to be considered to synchronize N applications with N sinks. There is a high potential to significantly increase the N use efficiencies across the NCP, however this should be done based on a scientific approach that considers N budgets for sustainable maximum yields while maximizing N use efficiencies. It can be concluded that among the management practices which give similar yields, the ones that increase the CSNUE would clearly provide the information on the potential to reduce N applications for economic and environmental benefits with sustainable crop productions.

Acknowledgements This work was supported in part by the National Natural Science Foundation of China (30570335) and the Chinese Academy of Sciences (grants KSCXZ-YW-N-037).

references

Amans, E.B., Slangen, J.H.G., 1994. The effect of controlledreleased fertilizer ‘Osmocote’ on growth, yield, and composition of onion plants. Fert. Res. 37, 79–84. Basso, B., Ritchie, J.T., 2005. Impact of compost, manure and inorganic fertilizer on nitrate leaching and yield for a 6-year maize–alfalfa rotation in Michigan. Agric. Ecosys. Env. 108, 329–341.

145

Bausch, W.C., Delgado, J.A., 2003. Ground base sensing of plant nitrogen status in irrigated corn to improve nitrogen management. In: VanToai, T., Major, D., McDonald, M., Schepers, J., Tarpley, L. (Eds.), Digital Imaging and Spectral Techniques: Applications to Precision Agriculture and Crop Physiology, vol. 66. American Society of Agronomy Spec. Publ., Madison, WI, pp. 145–157. Bjorneberg, D.L., Westermann, D.T., Aase, J.K., 2002. Nutrient losses in surface irrigation runoff. J. Soil Water Conserv. 57, 524–529. Braun-Luebbe Analyzing Technologies Inc., 1987. Technicon Industrial Systems. TRAACS 800 Continues-Flow Analytical System Tech. Publ. No. DSM-005-00.4. Brian-Luebbe Analyzing Technologies, Elmsford, NY. Bundy, L.G., Meisinger, J.J., 1994. Nitrogen availability indices. In: Weaver, R.W., et al. (Eds.), Methods of Soil Analysis: Part 2. Biological Methods. Soil Sci. Soc. Am. Monograph No. 5. Soil Sci. Soc. Am, Madison, WI, pp. 951–984. Council of European Communities, 1998. Council Directive 98/ 83/EC of 3 November 1998 on the quality of water intented for human consumption. Council of European Communities, Brussels. Davies, D.B., Sylvester-Bradley, R., 1995. The contribution of fertilizer nitrogen to leachable nitrogen in the UK: a review. J. Sci. Food Agric. 68, 399–406. Day, P.R., 1965. Particle fractionation and particle-size analysis. In: Black, C.A. (Ed.), Methods of Soil Analysis. Part 1. Physical and Mineralogical Properties. Including Statistics of Measurements and Sampling. ASA, Madison, WI, pp. 545–567. Delgado, J.A., 1998. NLEAP facts about nitrogen management. J. Soil Water Conserv. 53, 332–338. Delgado, J.A., 2001. Use of simulations for evaluation of best management practices on irrigated cropping systems. In: Shaffer, M.J., Ma, L., Hansen, S. (Eds.), Modeling Carbon and Nitrogen Dynamics for Soil Management. Lewis Publications, Boca Raton, FL, pp. 355–381. Delgado, J.A., 2002. Quantifying the loss mechanisms of nitrogen. J. Soil Water Conserv. 57, 389–398. Delgado, J.A., 2004. Use of best management practices and a nitrogen leaching index to maximize N recovery and protect ground water for high risk cropping systems—landscape combinations systems. In: Proceedings of the Ontario Nitrogen Forum. Niagara Falls, Ontario, Canada, March 3–4 (CD-ROM). Delgado, J.A., Mosier, A.R., 1996. Mitigation alternatives to decrease nitrous oxides emissions and urea-nitrogen loss and their effect on methane flux. J. Env. Qual. 25, 1105–1111. Delgado, J.A., Shaffer, M., Hu, C., Lavado, R.S., Cueto Wong, J., Joosse, P., Li, X., Rimski-Korsakov, H., Follett, R., Colon, W., Sotomayor, D., 2006. A decade of change in nutrient management: a new nitrogen index. J. Soil Water Conserv. 61, 63–71. Delgado, J.A., Follett, R.F., Shaffer, M.J., 2000. Simulation of NO3-N dynamics for cropping systems with different rooting depths. J. Soil Sci. Soc. Am. 64, 1050–1054. Delgado, J.A., Riggenbach, R.R., Sparks, R.T., Dillon, M.A., Kawanabe, L.M., Ristau, R.J., 2001. Evaluation of nitratenitrogen transport in a potato–barley rotation. J. Soil Sci. Soc. Am. 65, 878–883. Delgado, J.A., Khosla, R., Bausch, W.C., Westfall, D.G., Inman, D., 2005. Nitrogen fertilizer management based on site specific management zones reduce potential for nitrate leaching. J. Soil Water Conserv. 60, 402–410. Delgado, J.A., Bausch, W.C., 2005. Potential use of precision conservation techniques to reduce nitrate leaching in irrigated crops. J. Soil Water Conserv. 60, 379–387. Diez, J.A., Roman, R., 1997. Nitrate leaching from soils under a maize–wheat–maize sequence, two irrigation schedules

146

agricultural water management 89 (2007) 137–147

and three types of fertilizers. Agric. Ecosys. Env. 65, 189–199. Dowdy, S., Wearden, S., 1991. Statistics for Research, second ed. John Wiley & Sons, New York, NY, 629 pp. Eghball, B., Wienhold, B.J., Gilley, J.E., Eigenberg, R.A., 2002. Mineralization of manure nutrients. J. Soil Water Conserv. 57, 470–473. Fedkiw, J. (Ed.), 1991. Nitrate occurrence in U.S. waters and related questions: a reference summary of published sources from an agricultural perspective. USDA, Washington, DC. Follett, R.F., Keeney, D.R., Cruse, R.M. (Eds.), 1991. Managing Nitrogen for Groundwater Quality and Farm Profitability. Soil Sci. Soc.Am. J. Inc, Madison, WI, pp. 9–18. Follett, R.F. (Ed.), 1989. Nitrogen Management and Ground Water Protection. Elsevier Science Publishers, Amsterdam, 395 pp. Follett, R.F., Delgado, J.A., 2002. Nitrogen fate and transport in agricultural systems. J. Soil Water Conserv. 57, 402–408. Gunasena, H.P.M., Harris, P.M., 1968. The effect of time of application of nitrogen and potassium on the growth of the second early potato variety. Craigs R. J. Agric. Sci. 71, 283–296. Health Canada, 1996. Guidelines for Canadian Drinking Water Quality, sixth ed. Canadian Government Publisher, Ottawa. Hall, M.D., Shaffer, M.J., Waskom, R.M., Delgado, J.A., 2001. Regional nitrate leaching variability: What makes a difference in Northeastern Colorado. J. Am. Water Resour. Assoc. 37, 139–150. Hallberg, G.R., 1989. Nitrate in ground water in the United States. In: Follett, R.F. (Ed.), Nitrogen Management and Ground Water Protection. Elsevier, New York, NY, pp. 35– 74. Hergert, G.W., 1986. Nitrate leaching through sandy soil as affected by sprinkler irrigation management. J. Env. Qual. 15, 272–278. Hu, C., Cheng, Y., Yu, G., 2001. Effects of nitrogenous fertilizer application on nitrate-N concentration of soil solution on North China Plain. Resour. Sci. 23, 46–48 [in Chinese]. Hu, C., Delgado, J.A., Zhang, X., Ma, L., 2005. Assessment of groundwater use by wheat (Triticum aestivum L.) in the Luancheng Xian region and potential implications for water conservation in the northwestern North China Plain. J. Soil Water Conserv. 60, 80–88. Hu, C., Saseendran, S.A., Green, T.R., Ma, L., Li, X., Ahuja, L.R., 2006. Evaluating nitrogen and water management in a double cropping system using RZWQM. Vadoze Zone J. 5, 493–505. Juergens-Gschwind, S., 1989. Ground water nitrates in other developed countries (Europe)—relationships to land use patterns. In: Follett, R.F. (Ed.), Nitrogen Management and Ground Water Protection. Elsevier, New York, NY, pp. 75– 138. Khaleel, R., Reddy, K.R., Overcash, M.R., 1980. Transport of pollutants in runoff water from land areas receiving animal wastes: a review. Water Res. 14, 421–436. Khosla, R., Fleming, K., Delgado, J.A., Shaver, T., Westfall, D., 2002. Use of site specific management zones to improve nitrogen management for precision agriculture. J. Soil Water Conserv. 57, 513–518. Klute, A., 1965. Laboratory measurements of hydraulic conductivity of saturated soil. In: Black, C.A. (Ed.), Methods of Soil Analysis. Part 1. Physical and Mineralogical Properties. Including Statistics of Measurements and Sampling. ASA, Madison, WI, pp. 210–221. Li, W., Li, L., 2005. Effects of intercropping and nitrogen application on nitrate present in the profile of an Orthic Anthrosol in Northwest China. Agric. Ecosys. Env. 105, 483–491.

Liu, X., Ju, X., 2003. Nitrogen dynamics and budgets in a winter wheat–maize cropping system in the North China Plain. Field Crops Res. 83, 111–124. Liu, X., Ju, X., Zhang, Y., Hu, C., Kopsch, J., Fusuo, Z., 2006. Nitrogen deposition in agroecosystems in the Beijing area. Agric. Ecosys. Env. 113, 370–377. Meisinger, J.J., Delgado, J.A., 2002. Principles for managing nitrogen leaching. J. Soil Water Conserv. 57, 485–498. Milburn, P., Richards, J.E., Gartley, C., Pollock, T., O’Neill, H., Bailey, H., 1990. Nitrate leaching from systematically tiled potato fields in New Brunswick. Can. J. Env. Qual. 19, 448–454. Moreno, F., Cayuela, J.A., Fernandez, J.E., Fernandez-Boy, E., Murillo, J.M., Cabrera, F., 1996. Water balance and nitrate leaching in an irrigated maize crop in SW Spain. Agric. Water Manage. 32, 71–83. Newbould, P., 1989. The use of nitrogen fertilizer in agriculture. Where do we go practically and ecologically? Plant Soil 115, 297–311. Randall, G.W., Goss, M.J., 2001. Nitrate losses to surface water through subsurface, tile drainage. In: Follett, R.F., Hatfield, J.L. (Eds.), Nitrogen in the Environment: Sources, Problems, and Management. Elsevier Science B.V., Amsterdam, pp. 95–122. Randall, G.W., Iragavarapu, T.K., 1995. Impact of long-term tillage systems for continuous corn on nitrate leaching to tile drainage. J. Env. Qual. 24, 360–366. Randall, G.W., Huggins, D.R., Russelle, M.P., Fuchs, D.J., Nelson, W.W., Anderson, J.L., 1997. Nitrate losses through subsurface tile drainage in conservation reserve program, alfalfa, and row crop systems. J. Env. Qual. 26, 1240–1247. Rauch, F.D., Murakami, P.K., 1994. Comparison between two controlled-release fertilizers on selected foliage plants in an artificial potting mix. Fert. Res. 39, 89–95. Rimski-Korsakov, H., Rubio, G., Lavado, R.S., 2004. Potential nitrate losses under different agricultural practices in the Pampas Region, Argentina. Agric. Water Manage. 65, 83–94. Russelle, M.P., Deibert, E.J., Hauck, R.D., Stevanovic, M., Olson, R.A., 1981. Effects of water and nitrogen management on yield and 15N-depleted fertilizer use efficiency of irrigated corn. Soil Sci. Soc. Am. J. 45, 553–558. Schroder, H., 1985. Nitrogen losses from Danish agriculture— trends and consequences. Agric. Ecosyst. Env. 14, 279–289. Shaffer, M.J., 2002. Nitrogen modeling for soil management. J. Soil Water Conserv. 57, 417–425. Shaffer, M.J., Delgado, J.A., 2002. Essentials of a national nitrate leaching index assessment tool. J. Soil Water Conserv. 57, 327–335. Shoji, S., Gandeza, A.T. (Eds.), 1992. Controlled Release Fertilizers with Polyolefin Resin Coating. Konno Printing Co., Sendai, Japan. Shoji, S., Delgado, J.A., Mosier, A., Miura, Y., 2001. Use of controlled release fertilizers and nitrification inhibitors to increase nitrogen use efficiency and to conserve air and water quality. J. Comm. Soil Sci. Plant Anal. 32, 1051–1070. Smika, D.E., Heermann, D.F., Duke, H.R., Batchelder, A.R., 1977. Nitrate-N percolation through irrigated sandy soil as affected by water management. Agron. J. 69, 623–626. Spalding, R.F., Exner, M.E., 1993. Occurrence of nitrate in groundwater—a review. J. Env. Qual. 22, 392–402. Sun, Z.H., Liu, L.Q., Yang, S.C., 1993. Investigations on N content in the rainfall and soil leaching in Beijing. Soils Fert. 2, 8–10 (in Chinese). U.S. Environmental Protection Agency (EPA), 1989. National Primary and Secondary Drinking Water Regulations, Proposed Rule, Fed. Reg., 54: 22077. USEPA, Washington, DC. USDA-SCS (United States Department of Agriculture Soil Conservation Service), 1988. National Agronomy Manual, second ed. U.S. Gov. Print., Washington, DC.

agricultural water management 89 (2007) 137–147

Vigil, M.F., Eghball, B., Cabrera, M.L., Jakubowski, B.R., Davis, J.G., 2002. Accounting for seasonal nitrogen mineralization: an overview. J. Soil Water Conserv. 57, 464–469. Westermann, D.T., Kleinkopf, G.E., 1985. Nitrogen requirements of potatoes. Agron. J. 77, 616–621. Zhang, W.L., Tian, Z.X., Zhang, N., Li, X., 1996. Nitrate pollution of groundwater in northern China. Agric. Ecosyst. Env. 59, 223–231. Zhang, W., Tian, Z., Li, X., 1995. Survey of nitrate contamination in groundwater in relation to N fertilizer use in North China. Plant Nutr. Fert. Sci. 1, 80–86 (in Chinese). Zhang, X., Pei, D., Hu, C., 2003. Conserving groundwater for irrigation in the North China Plain. Irrig. Sci. 21, 159–166.

147

Zhang, Y.M., Hu, C.S., Zhang, J.B., Chen, D.L., Li, X.X., 2005. Nitrate leaching in an irrigated wheat-maize rotation field in the North China Plain. Pedosphere 15, 196–203. Zhang, X. (Ed.), 1999. Crop Root System and Soil Water Utilization. Meteological Press, Beijing (in Chinese). Zhu, Z.L., Chen, D.L., 2002. Nitrogen fertilizer use in China— contributions to food production, impacts on the environment and best management strategies. Nutr. Cycl. Agroeco. 63, 117–127. Zhu, A., Zhang, J., 2005. Water balance and nitrate leaching losses under intensive crop production with Ochric Aquic Cambosols in North China Plain. Env. Int. 31, 904–912. Zitong, G. (Ed.), 1999. Chinese Soil Taxonomy. Sciences Press, Beijing (864 pp., in Chinese).