Quantification of C and N stocks in grassland topsoils in a Dutch region dominated by dairy farming

Estimates on soil organic carbon (SOC) and nitrogen (N) stocks in soils cannot be directly calculated from routine soil analyses, since these often lack measurements on soil bulk density (Bd). Hence, flexible pedotransfer functions are required that allow the calculation of SOC stocks from gravimetrically determined SOC contents. The present paper aimed to: (1) quantify SOC and N stocks in grassland topsoils for a Northern Dutch region dominated by dairy farming and (2) analyse the relationships between SOC and bulk density at the field level. As estimates of SOC and N stocks are potentially affected by soil compaction, the combined measurements on soil bulk density and soil organic matter (SOM) were also evaluated with respect to critical limits for soil compaction using soil density (Sd) for sandy soils and packing density (Pd) for clay soils. The SOC and Bd measurements were done in the upper 0·1–0·2 m of grasslands at 18 dairy farms, distributed across sandy, clay and peat soils. Both farm data and grassland management data were collected. Non-linear regressions were used to analyse relationships between Bd and SOM. Significant non-linear relationships were found between gravimetric SOC contents and bulk density for the 0–0·1 m layer (R2=0·80) and the 0·1–0·2 m layer (R2=0·86). None of the fields on sandy soils or clay soils indicated signs for limited rooting in the topsoil although some fields appear to approach the critical limit for compaction for the 0·1–0·2 m layer. Stocks of SOC in the top 0·2 m at farm level were highest in the peat soils (21·7 kg/m2) and lowest in the sandy soils (9·0 kg/m2). Similarly, N stocks were highest for farms on peat soil (1·30 kg/m2) and lowest for farms on sandy soil (0·60 kg/m2). For the sandy soils, the mean SOC stock was significantly higher in fields with shallow groundwater tables

Maaiveldsdaling van veengrasland bij twee slootpeilen in de polder Zegvelderbroek : vijfentwintig jaar zakkingsmetingen op het ROC Zegveld

De maaiveldsdaling van veengrond zonder kleidek is bij twee polderpeilen vastgesteld door in 1966 en 1992 de maaiveldhoogte te meten. Onderzocht is wat het aandeel van de klink is en hoe het verlies aan veen door oxidatie over de diepte verdeeld is. Bij een hoog polderpeil zakt het maaiveld in 25 jaar 0,167 m (6,7 mm/a). Een verlaagd slootpeil van constant 0,70 m beneden maaiveld geeft in dezelfde periode een maaiveldsdaling van 0,396 m (15,8 mm/a). Door de peilverlaging wordt het oxidatieverlies meer dan verdubbeld tot 10,9 mm/a. Een hoger aandeel minerale delen in de bovengrond kan meer of minder oxidatie geven. De klink is een doorgaand proces

Diminishing peat oxidation of agricultural peat soils by infiltration via submerged drains

Oxidation of peat soils used in dairy farming in the western peat area of The Netherlands causes subsidence rates up to 13 mm.y and emissions of CO2 to about 27 t.ha.y. In 2003 experiments started with subsurface irrigation by submerged drains to raise groundwater levels to reduce oxidation and so subsidence and GHG emissions. Subsidence and so CO2 emissions were reduced with at least 50% and the trafficability improved. The advantages of submerged drains for dairy farmers beside the reduction of subsidence are the improved trafficability, reduced drought risk and reduced loss of grass yield in wet periods by trampling. This makes for dairy farmers the use of submerged drains an acceptable solution in contrary to the often suggested solution to raise ditchwater levels. This acceptance by dairy farmers makes submerged drains a promising tool to preserve the valued cultural historic peat soil landscape