Impact of fertilizer type and rate on carbon and nitrogen pools in a sandy Cambisol

Abstract

Type and rate of fertilizers influence the level of soil organic carbon (C org ) and total nitrogen (N t ) markedly, but the effect on partitioning of C and N into different pools is open to question. Objectives were to investigate the impact of fertilizer type and rate on labile, intermediate and passive C and N pools in a sandy Cambisol at Darmstadt, Germany, after 27 years of different fertilization treatments. The six treatments were: straw incorporation plus application of mineral fertilizer (MSI) and application of farmyard manure (FYM) each at high (140-150 kg N ha −1 year −1 ), medium (100 kg N ha −1 year −1 ) and low (50-60 kg N ha −1 year −1 ) rates. Soil microbial biomass C (C mic ) and N (N mic ) and C and net N mineralization (266 days incubation at 10°C and 50% waterfilled pore space) were determined. Soils (0-25 cm) of MSI treatments had significantly (p≤0.05) lower C mic stocks (308-361 kg ha −1 ) than soils of FYM treatments (404-520 kg ha −1 ). Differences in N mic stocks were less pronounced. After 266 days, mineralized C (1130-1820 kg ha −1 ) and N (90-125 kg ha −1 ) had significantly increased with fertilizer rate. The application of an exponential two-pool model showed that very labile pools (turnover times: 17 and 9 days for C and N, respectively) were small (1.3-1.8% of C org and 0.5-1.0% of N t ) and not influenced by type or rate of fertilizer. Stocks of the modeled labile C and N pools (turnover times: 462 and 153 days for C and N, respectively) were not influenced by the type of fertilizer but depended significantly on the application rate and ranged from 7 to 13% of C org and from 4 to 5% of N t . In contrast, the size of the calculated intermediate C pool was greater for the FYM treatments, and depended significantly on the interaction of fertilizer type and rate. The intermediate N pool was unaffected by fertilizer type or rate. Passive C and N pools, as experimentally revealed by oxidation with disodium peroxodisulfate (Na 2 S 2 O 8 ), were independent of the treatments. Overall, labile and intermediate pools were affected differently by the fertilizer type and the application rate.

Effects of fertilization and soil management on crop yields and carbon stabilization in soils. A review

“…II) but depended significantly on the application rate and ranged from 7 to 13% of SOC and from 4 to 5% of total N (Heitkamp et al, 2009). In contrast, the size of the calculated intermediate C pool was greater for the manure treatments (Tab.…”

“…In the four-year course of the crop rotation from 2003 to 2006, measured mean annual C inputs (t ha −1 year −1 ) with straw were between 1.0 and 1.2 in the NPK and straw treatments, whereas measured differences in C inputs from manure were more pronounced and ranged from 0.6 to 1.3 in the manure treatments (Heitkamp et al, 2009).…”

“…The soil is a Haplic Cambisol (WRB, 2006) which developed on alluvial fine sands of the former river Neckar (Bachinger, 1996). The soil has a sand and clay content in the surface soil of 86% and 5%, respectively, and bulk density ranges from 1.35 to 1.41 g cm −3 (Heitkamp et al, 2009). Before the trial started, the site was managed as part of a biodynamic farm for at least 20 years (Abele, 1987).…”

“…To account for the structure of the strip design we applied a mixed model in order to test for significant (P 0.05) effects of the treatments on crop yields and SOC fractions (Heitkamp et al, 2009). The field trial was divided into main rows and main columns.…”

Intensive Management in Grasslands Causes Diffuse Water Pollution at the Farm Scale

“…The high rates of C export support the notion that agricultural catchments, particularly pastoral systems, yield higher C losses than do forested or seminatural catchments (Graeber et al, 2012). Increased C losses from agricultural catchments may be caused by manure applications and grazing causing an increase in soil dissolved organic matter concentration through stimulation of microbial activity and increased oxygenation of the agricultural soils (Chantigny, 2003;Heitkamp et al, 2009) and higher erosion rates (Hope et al, 1997a;Quinton et al, 2010) transporting high rates of particulate C. The few studies that quantified DOC and particulate C in agricultural landscapes showed a high contribution of particulate carbon to overall C losses by low DOC/TOC ratios (up to 1.01) and 58 and 42% of organic C losses as DOC and particulate organic C, respectively (Stutter et al, 2008). Therefore, studies measuring C cycling and C losses from agricultural land to freshwater should include TC as up to 50% of C losses may not be accounted for (Quinton et al, 2006).…”