fertilizer-N Inputs Research Articles

Management Drives Differences in Nutrient Dynamics in Conventional and Organic Four-Year Crop Rotation Systems

Application of exogenous N fertilizers provides agronomic benefits but carries environmental liabilities. Managing benefits and liabilities of N-based fertilizers in conventional (CNV) and organic (ORG) cropping systems might be improved with better knowledge of nutrient dynamics, the generation of intrinsic N, and maintenance of soil organic matter. This study evaluated mineral N dynamics, yields, residue inputs, and change in soil organic C (SOC) and total N (TN) in strip-tilled, four-year crop rotations [corn (Zea mays L.)-soybean (Glycine max [L.] Merr.)-wheat under-seeded with alfalfa (Triticum aestivum L./Medicago sativa L.)-alfalfa] over eight years of production under CNV management using mineral-N (NO3NH4) and chemical pesticides or ORG management using organic-N (animal manure) and no chemical treatments. In ORG, N availability increased over time, but did not benefit ORG yields due to poor control of insects and weeds. Corn, soybean, and wheat grain yields were 1.9 to 2.7 times greater in CNV. In general, SOC was lost in CNV but did not change in ORG. Cumulative yield N removals exceeded cumulative fertilizer-N inputs by an average of 78% in CNV and 64% in ORG. These results indicated ORG management supported N availability by generating intrinsic N.

Productivity and the complementary use of nitrogen in the coupled rice-crab system

Agricultural intensification has greatly increased yields but has also negatively affected the environment. The coupling of two agricultural systems (i.e., integrated agriculture-aquaculture or integrated crop-livestock) has been proposed as one of the important ways that reduce the negative effects of agriculture on the environment, but large-scale experimental data are lacking. In this study, we examined the coupled rice-crab system, which is a rapidly developing rice-fish system in China. We conducted a field survey across several rice-planting areas and field and mesocosm experiments to determine whether the rice-crab system achieves high yields of both rice and crab without damaging the environment. Our field survey showed that rice yield was not reduced in the rice-crab system across four rice-growing areas although total fertilizer N was reduced compared to rice monoculture. Our field experiment also showed that the rice-crab treatment produced higher rice yield than rice monoculture treatment with the same fertilizer N application, and that the coupled rice-crab treatment had higher crab yield with less crab numbers of precocious maturation than the crab monoculture treatment with the same amount of feed. Both field and mesocosm experiments showed that the rice-crab system did not cause serious feed-N accumulation in the field. Isotope 15N labeling indicated that rice plants used 7.6% of the feed-N. Dual isotope 13C/15N analysis showed that 59.1% of the food consumed by crabs consisted of organisms that thrived by directly using nutrients in the field. This recycling of N within the field explains the low fertilizer-N input and low effluent-N in the coupled rice-crab system. Our results suggest that the coupling of rice with fish production can achieve synergies between food production systems to reduce environmental impacts per unit of production.

Grain yield, water productivity and nitrogen use efficiency of rice under different water management and fertilizer-N inputs in South China

The increasing scarcity of irrigation water necessitates the development of water-saving technology in rice production. Our previous studies have shown that “safe” alternate wetting and drying irrigation (AWD15) can effectively save water, improve water productivity while maintain grain yield compared to continuous flooding (CF) and farmer's water management practice (FP) under a single fertilizer-N input. The objectives of this study are (1) to investigate the superiority of this novel water management practice compared with FP; and (2) to examine whether there is an interaction between water and N input and whether fertilizer-N input needs to be adjusted under AWD15. Two field experiments were conducted during the late cropping seasons of 2014 and 2015. A hybrid rice variety Tianyou3618 was grown under two water management (AWD15 and FP) and four fertilizer-N rates (0, 90, 180, 270kgNha−1). Grain yield, water productivity and nitrogen use efficiency were determined. Compared to that of FP, irrigation water input of AWD15 was reduced by 24.1% in 2014 and 71.4% in 2015. The number of irrigations decreased and water productivity increased significantly. No significant differences existed between AWD15 and FP in grain yield, biomass, leaf area index and nitrogen use efficiency. Nitrogen input level had significant effects on yield, biomass, harvest index and nitrogen use efficiency in both years. Grain yield increased with N rate and the optimal N rate was 180kgNha−1. No significant interaction was found between water and nitrogen rate regarding biomass production and grain yield. Our results demonstrated that no change in N input is needed under AWD15 condition and AWD15 is advantageous over farmer's water management practice under all N levels investigated in South China. This is the first report on the performance of AWD15 under different fertilizer-N levels in South China.

Maintaining yields and reducing nitrogen loss in rice–wheat rotation system in Taihu Lake region with proper fertilizer management

In the Tailake region of China, heavy nitrogen (N) loss of rice–wheat rotation systems, due to high fertilizer-N input with low N use efficiency (NUE), was widely reported. To alleviate the detrimental impacts caused by N loss, it is necessary to improve the fertilizer management practices. Therefore, a 3 yr field experiments with different N managements including organic combined chemical N treatment (OCN, 390 kg N ha−1 yr−1, 20% organic fertilizer), control–released urea treatment (CRU, 390 kg N ha−1 yr−1, 70% resin-coated urea), reduced chemical N treatment (RCN, 390 kg N ha−1 yr−1, all common chemical fertilizer), and site-specific N management (SSNM, 333 kg N ha−1 yr−1, all common chemical fertilizer) were conducted in the Taihu Lake region with the ‘farmer’s N’ treatment (FN, 510 kg N ha−1 yr−1, all common chemical fertilizer) as a control. Grain yield, plant N uptake (PNU), NUE, and N losses via runoff, leaching, and ammonia volatilization were assessed. In the rice season, the FN treatment had the highest N loss and lowest NUE, which can be attributed to an excessive rate of N application. Treatments of OCN and RCN with a 22% reduced N rate from FN had no significant effect on PNU nor the yield of rice in the 3 yr; however, the NUE was improved and N loss was reduced 20–32%. OCN treatment achieved the highest yield, while SSNM has the lowest N loss and highest NUE due to the lowest N rate. In wheat season, N loss decreased about 28–48% with the continuous reduction of N input, but the yield also declined, with the exception of OCN treatment. N loss through runoff, leaching and ammonia volatilization was positively correlated with the N input rate. When compared with the pure chemical fertilizer treatment of RCN under the same N input, OCN treatment has better NUE, better yield, and lower N loss. 70% of the urea replaced with resin-coated urea had no significant effect on yield and NUE improvement, but decreased the ammonia volatilization loss. Soil total N and organic matter content showed a decrease after three continuous cropping years with inorganic fertilizer application alone, but there was an increase with the OCN treatment. N balance analysis showed a N surplus for FN treatment and a balanced N budget for OCN treatment. To reduce the environmental impact and maintain a high crop production, proper N reduction together with organic amendments could be sustainable in the rice–wheat rotation system in the Taihu Lake region for a long run.

Improving agronomic practices to reduce nitrate leaching from the rice–wheat rotation system

Winter wheat–summer rice rotation with unique dry–wet cycle water regime is one of the most general cropping systems in the Yangtze Delta, which might favor NO3−-N leaching into shallow groundwater due to high fertilizer-N input with low N use efficiency. To alleviate the detrimental impacts caused by N leaching, it is necessary to apply improved management practices. Therefore, the objectives of the present study are to investigate characteristics of N leaching under drained upland crop-flooded rice rotation and illustrate the effectiveness of an improved agronomic practice for mitigating NO3−-N leaching. N leaching measured in situ for the control (CK), conventional (CT), and improved (IT) treatments for one rice–wheat rotation. Improved fertilization and crop cultivation managements have been applied to the IT treatment in an integrated manner, including low N fertilization rate, high fertilization frequency, and dense planting. During the rice-growing season, NO3–-N and dissolved organic N (DON) were the predominant forms of N in percolation water, and contributed over 25% and 59% to TN, respectively. NO3–-N and TN concentrations in percolation water and leaching losses did not differ significantly (p>0.05) between treatments. N leaching occurred mainly during the early stage of rice seedling transplanting. During the wheat-growing season, N in percolation water was predominantly in the form of NO3–-N, and accounted for over 64.5–82.9% of TN. N fertilization significantly increased NO3–-N and TN concentrations in percolation water. Nitrate and TN leaching losses from the IT treatment (1.15 and 1.38kg Nha−1, respectively) were smaller than the CT treatment (1.34 and 1.76kg Nha−1, respectively). The majority of N leaching losses for wheat occurred during the period from late February to final harvest. The IT treatment exhibited no significant effect on wheat yield, but significantly (p<0.05) increased rice yield (8.60Mgha−1 compared to 8.06Mgha−1) relative to the CT treatment. Compared with the conventional management practice, the improved management practice appeared to be effective in reducing N leaching and increasing grain yield under the rice–wheat rotation.

Crop production for biogas and water protection—A trade-off?

In Germany the promotion of renewable energy has led to a rapid expansion of biogas production in recent years. Growing controversy surrounds this development due to potential environmental trade-offs caused by biomass production for co-fermentation, which is dominated by silage maize. The aim of the study was to evaluate the N-leaching potential following application of biogas residues and animal slurry to grassland and maize on a sandy soil in northern Germany.The study was based on a field experiment conducted in northern Germany over two consecutive leaching periods (2007/2008 and 2008/2009). Treatments included N-fertilizer type (co-fermented biogas residue, cattle slurry, calcium ammonium nitrate) and N amount (grass: 0, 160, 320 and 480kgNha−1; maize: 0, 120, 240 and 360kgNha−1). The fertilizer amount was split into two (maize) or four (grass) dressings. Leachate was collected using ceramic suction cups installed at 60cm depth. Water fluxes were simulated with a site-adapted model in which the soil water balance calculation was based on mechanistic approaches, while crop height and green area index were quantified by simple logistic growth equations. Nitrogen load was obtained by combining the simulated leachate amount with measured N concentration.Water fluxes, crop height and green area index were satisfactorily simulated. Nitrate-N loss in grassland generally was very low, staying below the critical nitrate-N load, according to the EU drinking water threshold. At optimal N input, i.e. N input required for maximum yield, maize caused a considerable nitrate-N load (48–67kgha−1), and it increased exponentially at higher inputs. Most of the variation of nitrate-N load among fertilizer types was explained by the proportion of fertilizer-N input as mineral N. For both grassland and maize, biogas residues had a similar nitrate leaching potential to animal manures. Maize achieved a substantially higher methane hectare yield (mN3 CH4 ha−1) than grassland. This could not overcompensate for its higher nitrate-N load, as indicated by the eco-efficiencies in terms of kg nitrate-N load per mega liter methane produced at optimal N input (maize: 7.7–14.7, grass: 0.3–2.9).

Nitrogen use efficiency: re-consideration of the bioengineering approach

There is considerable confusion about N use efficiency (NUE) in the plant literature. We would like to propose the simple and ubiquitous definitions described by Good et al. (2004) as a starting point for studies of NUE. Based on this terminology, there is evidence from breeding programs for variation in both uptake efficiency (UpE) and utilization efficiency (UtE). Molecular physiology studies typically address mechanisms for improving NUE, but often do not calculate NUE or even acquire appropriate data for calculating NUE. Herein, we report in detail on recent studies involving molecular approaches for improving NUE, and calculate changes in NUE where possible. The evidence suggests that there is potential for improving usage index and UpE in dicots and UpE and UtE in monocots by overexpressing enzymes for N assimilation, specifically glutamine synthetase 1, glutamate synthase, and alanine aminotransferase. If decreased fertilizer-N input and improved NUE are truly goals of the plant biology community, researchers are encouraged to (i) consider the use of both wild type and azygous controls, (ii) compare general NUE (on the basis of grain or biomass yield per unit of applied N) of overexpression mutants and controls at both limiting and non-limiting N levels, (iii) select an appropriate type of specific NUE for assessing the physiological mechanisms involved (uptake versus internal utilization), and (iv) confirm promising results under field conditions.

Study of nitrate leaching and nitrogen fate under intensive vegetable production pattern in northern China

Because of intensive vegetable production in plastic greenhouses in northern China, the potential risk of nitrate leaching to groundwater is increasingly apparent, threatening ecosystem services and the sustainability of food production. In the present work, nine drainable lysimeters were installed into vegetable fields, with in-situ loamy soils, in Shouguang City of the north China vegetable base. The experiments were conducted to quantify the magnitude and variability of nitrate leaching to groundwater and to access the fate of total fertilizer-N inputs in the area. The results obtained indicated that: under local conventional agronomic practices, there is a high discrepancy in leaching nitrate-N concentration (ranging from 17 to 457 mg L −1), and nitrate losses (152–347 kg N ha −1) were observed from 1-m soil profiles in the field. Meanwhile, high fertilizer N application resulted in low N efficiency, with only ( 33.0 ± 13 ) % ( mean ± S.D. ) of input N absorbed by the crops, while additionally nearly half of the total inputs of N were unaccounted in a partial N balance sheet. It is concluded that groundwater pollution associated with greenhouse-based vegetable production had been confirmed in Shouguang, adversely affecting water quality and leading to serial agro-ecological problems. To cite this article: X.-Z. Song et al., C. R. Biologies 332 (2009).

Farmer participatory testing of standard and modified site-specific nitrogen management for irrigated rice in China

Rice in China receives high amounts of fertilizer nitrogen (N) that are often not used efficiently by the crop. A recently developed site-specific N management (SSNM) approach enables the application of fertilizer N to dynamically match the field- and season-specific needs of the rice crop for N. We used farmer participatory research for on-farm testing of N fertilization by standard and farmer-modified SSNM for irrigated rice. Our study was done in 14 villages in four provinces of China in 2003 and 2004. Twelve to 15 farmers were randomly selected in each study village in each year for a dialogue with the research team and for a rapid rural technology assessment (RRTA). Based on the information obtained from the RRTA, modified SSNM (MSSNM) schemes were developed through dialogue between a research team and farmers at a workshop in each village. Modification mainly involved decreasing the number of fertilizer-N topdressings and increasing the rate of basal N application. Among the 514 farmers surveyed during the workshops, 95% were willing to adopt SSNM and MSSNM technologies and 76% were willing to conduct SSNM or MSSNM experiments. More than two-thirds of the farmers preferred adopting MSSNM rather than the standard SSNM. Based on the farmers’ willingness, 144 farmers were selected to conduct an experiment to compare SSNM or MSSNM with the farmers’ fertilizer practices (FFP). The rate and distribution of fertilizer N during the growing season of MSSNM were in between those of SSNM and FFP. SSNM and MSSNM, compared with FFP, maintained rice yields with significantly less fertilizer N and no significant increase in total labour input. The reduction in fertilizer-N input averaged 48 kg N/ha for SSNM and 23 kg N/ha for MSSNM. The study suggests that there is potential for large-scale dissemination of SSNM technology in China.

The impact of modern farming practices on soil fertility and quality in England and Wales

Data are presented on the effects of modern farming practices on soil as an agricultural resource in England and Wales (E&amp;W), namely: nutrient status, pH, soil organic carbon (SOC), heavy metal concentrations, and on soil erosion risk. Fertilizer-N inputs to tillage (arable) and grassland soils increased from 84 and 65 kg/ha N in 1969 to 151 and 120 kg/ha N, respectively, in 1997. The estimated N surplus (inputs less outputs) increased from 84 and 96 kg/ha N to 102 and 154 kg/ha N, respectively, over the same time. Phosphorus inputs to tillage (mean 37 kg/ha P) and grassland (mean 21 kg/ha P) changed little over the period. However, P surpluses decreased from 25 kg/ha P in 1969 to 15 kg/ha P in 1997 on tillage land (largely as a result of greater P offtakes), and from 20 to 17 kg/ha P in 1997 on grassland (largely because of a small decrease in fertilizer P). The cumulative tillage land soil P surplus was c. 580 kg/ha P, and was estimated to increase topsoil total P concentrations by c. 170 mg/kg P and Olsen-extractable soil P by c. 26 mg/l P. The mean annual P surplus for grassland was 18 kg/ha P which, over the study period, added c. 427 kg/ha P to the soil, an increase in topsoil total P of c. 214 mg/kg P, and in Olsen-extractable P of 19 mg/l P.Concentrations of SOC in some soils have decreased between 1980 and 1995, especially where soils have been ploughed out of grassland and on lowland organic and peaty soils in tillage. The mean SOC of soils in arable/ley cultivation in 1980 was 3·4% and 2·8% in 1995.The proportion of arable soils with pH &lt; 6·0 decreased from 10% in 1969–73 to 4% in 1990–93, reflecting the better targeting of lime inputs. In contrast, the proportion of grassland soils with pH &lt; 6·0 increased from 39% in 1969–73 to 56% in 1990–93.Although there were statistically significant changes in the mean soil concentrations of Cd, Cu, Ni, Pb and Zn between 1980 and 1995, many of the changes were small in absolute terms. Hence, there was little evidence of marked or systematic changes in topsoil total heavy metal concentrations that could not be explained by factors other than increased pollutant loadings.Over the next 50 years or so, the threat from soil erosion to crop productivity will be greatest on shallow soils ([les ] c. 0·3 m depth), mostly over chalk and sandstone as further removal of soil will lead to increased drought stress. Provided that nutrient supplies are maintained, the evidence is that losses in arable crops on eroded soils would range between 2% and 8% of current yields.Thus, within the limitations of the data available, both in time and space, we found little evidence that most soils in E&amp;W cannot continue to support modern farming practices, and the associated crop and animal outputs, given appropriate inputs of nutrients and an adequate degree of crop protection.

Dissolved organic carbon losses from grazed grasslands under different management regimes

Dissolved organic matter (DOM) is fundamental to many biogeochemical processes in soils and natural waters. Despite the large number of studies reporting on DOM losses from forest soils and in surface waters there is little published data on exports from managed grasslands. The objective of our study was to determine the extent of short-term exports of dissolved organic carbon (DOC) from managed grazed grasslands and to evaluate the influence of fertilizer management and drainage regime. DOC discharged from grazed grassland plots, with a range of management strategies, was determined over 2 months. Total export varied from 42 to 118 kg C ha −1, and was greater from some plots than literature estimates for annual losses from all catchment types. There was a significant ( P=0.048) positive correlation between DOC export and rates of nitrogen application for treatments with no artificial drainage. Increased dry matter production arising from increased fertilizer-N inputs is suggested as an important factor in this relationship. DOC export was significantly ( P=0.032) reduced by artificial drainage and adsorption of DOC to soil surfaces and the restriction of decomposition due to waterlogging are suggested as two possible explanations.

Comparative effects of grain lentil–wheat and monoculture wheat on crop production, N economy and N fertility in a Brown Chernozem

Low commodity prices and a desire by producers on the Canadian Prairies to reduce fertilizer-N inputs have resulted in a marked increase in grain lentil (Lens culinaris medikus) production. Many producers grow lentil in rotation with spring wheat (Triticum aestivum L.). A 12-yr study carried out at Swift Current, Saskatchewan, on an Orthic Brown Chernozemic silt loam was used to compare the N economy of four monoculture wheat rotations, of various rotation lengths and levels of N fertilization, with that of a wheat–lentil (W–Len) rotation. Except for continuous wheat (Cont W) receiving mainly P fertilizer, all systems received N and P on the basis of soil tests. Neither grain nor straw yield of the associated wheat crop was influenced by lentil in the rotation; but grain- and straw-N concentrations of the wheat in W–Len were increased compared with those of monoculture wheat. Average N content of straw was greatest for grain lentil and for wheat grown on fallow (F) (14.2 kg ha−1 yr−1), followed by wheat in W–Len (11.8 kg ha−1 yr−1) and by stubble-wheat of well-fertilized monoculture systems (F–W–W and Cont W (9.5 kg ha−1 yr−1)), and lowest for Cont W receiving mainly P (5.7 kg ha−1 yr−1). Nitrate N in the root zone (0–90 cm) in spring and at harvest was greatest under F–W, followed by W–Len and then by F–W–W and Cont W receiving N and P, and lowest for Cont W receiving mainly P. In the last 5 or 6 yr of study, there was a marked increase in the amount of soil-NO3 N found in the root zone under the W–Len rotation. This was accompanied by a similar increase in the apparent net N mineralized (estimated by N balance) during the growing season. Concomitantly, there was a gradual reduction in the fertilizer-N requirement for W–Len, indicating a cumulative enhancement of the N-supplying power of the soil, although estimates of the initial potential rate of N mineralization on samples taken in 1990 did not confirm this trend. We concluded that soil-testing laboratories may need to adjust fertilizer-N recommendations downward for producers that regularly use a 2-yr W–Len rotation. There was less NO3 N leached below the root zone of W–Len, probably because there was greater synchrony of N uptake in W–Len than in Cont W (N + P); this augurs well for the use of the W–Len rotation for sustainability.Key words: Crop rotations, pulse crops, N mineralization, N fixation, N leaching