Comparing the effectiveness of radish cover crop, oilseed rape volunteers and oilseed rape residues incorporation for reducing nitrate leaching

摘要: The soil water and N dynamics have been studied during two long fallow periods (between wheat or oilseed rape a spring crop) in field experiment Châlons-en-Champagne (eastern France, 48°50′ N, 2°15′ E). involved frequent measurements of water, mineral dry matter uptake by cover crops. Water budgets were established using Ritchie's model for calculating evapotranspiration cropped soils (LIXIM) drainage, leaching mineralisation bare soils. During the first autumn winter, radish crop (grown from September 1994 to January 1995) was compared soil. second period (July 1995 April 1996), comparison carried out between (i) volunteers, (ii) with types residues incorporated into (R0 R270 residues) (iii) without incorporation. R0 came preceding crops which received rates fertilizer (0 270 kg ha-1). Soil content markedly reduced presence volunteers autumn. calculated actual (AET) did not differ much treatments, meaning that transpiration relatively low (100–150 L kg-1 matter). Consequently, nitrate rest winter as well concentration percolating water: 45 vs. 91 mg NO3 - L-1 soil, respectively. incorporation also exerted beneficial but smaller action on reducing This effect due extra immobilisation reached maximum about 20 ha-1 mid-autumn both residues. Nine months after residues, comparing control incorporation, rich induced significant positive net (+ 9 ha-1) corresponding 10% added whereas poor no still obtained at end (−3 ha-1, significantly different 0). To reduce periods, it is necessary promote techniques leading decrease mineral-N contents before drainage period, such residue harvest (without fertiliser-N) allowing grow sowing just last main crop.