Nitrate Leaching

Determination of nitrate leaching is the main focus for this study as per European Union and Netherlands’ regulations are concerned. As reported by Kladivko et al. (1997), most nitrate losses through subsurface drainage take place during autumn, winter and early spring. Moreover, the leaching rate is promoted by the tillage processes (Hansen and Djurhuus, 1997). Two soil water samplers (Eijkelkamp Agrisearch Equipment, Giesbeek, the Netherlands) were installed per sub-plot. Samplers consisted of 48 mm diameter polyvinylchloride cylinders with a 60 mm long ceramic cup fitted at the bottom end (Hansen and Harris 1975), (Vos and Van Der Putten, 2004). The ceramic cup were installed at 80 cm below the soil surface. Soil solution was extracted at

(2015). About 20g of each sample were combusted in a furnace at 5500C for ignition duration of three hours and a tray turning at half-time. The empty crucibles were weighed when hot at three decimals (A) in a drying oven at 1030C. about 5g of soil were weighed (W) then the crucibles with about 20g of soil sample were dried at 1030C for about 3 hours then weighed when hot (B). The crucibles were put in the furnace then raising temperature gradually from room temperature to 5500C then temperature of 5500C was maintained for about 3 hours. The furnace was cooled up to about 1500C then crucibles were put in drying oven at 1030C for about 1 hour before the hot crucibles with ash (C) were weighed. The dry matter content and SOM of the sample in percentage (%) was calculated as

The soil samples were first shaken for about two hours after putting the relevant solvent before pH measured in the settling suspension.
3.3.3 Soil bulk density, water content and porosity
Soil bulk density was measured in the three main plots and six sub-plots. Two rings of 5cm diameter each was used to collect the samples from three holes for the layers of 0-10cm, 10-20cm and 20-30cm per each sub-plot at any time in winter or spring if the soil is not too wet. The samples from each ring will be put in the bag, weighed then dried by oven at 1050C. Dry bulk density, water content and soil porosity will be measured using pycnometer method as described by Heiskanen (1992).
3.3.4 Soil penetration resistance
Soil penetration resistance was measured using the methods described by Kouwenhoven et al. (2002). A digital Eijkelkamp penetrologger was used for 20 measurements per each subplot in a systematic order at a depth of 60cm. The total measurements were conducted in March, 2016 during spring season with a total of 360 measurements for all three plots (NIT, ECO and CON).
3.3.5 Earthworm population and