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Effects of overwinter cover on nitrate loss and drainage from a sandy soil: consequences for water management?
Author(s) -
Shepherd M.A.,
Webb J.
Publication year - 1999
Publication title -
soil use and management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.709
H-Index - 81
eISSN - 1475-2743
pISSN - 0266-0032
DOI - 10.1111/j.1475-2743.1999.tb00073.x
Subject(s) - loam , lysimeter , cover crop , agronomy , environmental science , zoology , soil water , biology , ecology
. A lysimeter study from April 1993 to June 1997 assessed the effects of winter cover crops and unfertilized grass on both the volume of water draining over winter and the amounts of nitrate leached. There were three to five replicates of each treatment in a fully randomized design. The lysimeters were undisturbed monoliths of loamy medium sand, 1.2 m deep and 0.8 m diameter. There were six treatments: sown cover before spring‐sown crops (SC), natural regeneration (‘tumbledown’) before spring‐sown crops (T), unfertilized grass (UG), bare soil permanent fallow, (PF), winter barley (WB) and conventional overwinter fallow before spring‐sown crops (WF). Sugarbeet replaced cereals in 1996 as a disease break, and in consequence no cover was established in SC and T in autumn 1996. Of the four years of the study, two were above‐average rainfall, while two were of less than average rainfall. Results are only quoted if statistically significantly different from WB ( P =0.10). Over the first winter, NO 3 ―N losses were similar under UG (26 kg ha −1 ) and PF (29 kg ha −1 ), due to the slow establishment and growth of the grass. In the following three winters NO 3 ―N losses under UG were small ( c. 6 kg ha −1 ), giving an overall mean of c. 11 kg ha −1 . Sown cover crops and T gave means of c. 16 and 22 kg ha −1 respectively, compared with c. 27–31 kg ha −1 under PF, WB and WF. Mean NO 3 ―N concentrations were smallest under UG (4.4 mg l −1 ) and SC (10.6 mg l −1 ), although both T (13.7 mg l −1 ) and PF (12.4 mg l −1 ) were less than under WB and WF (15.8–18.7 mg l −1 ). Overwinter drainage was greatest from UG and PF, at 239 and 247 mm respectively. In the three winters that cover crops were grown, drainage was decreased by, on average, 30 mm year −1 compared with WF. However, there were large differences in effects between years, with significant decreases in only one year. We conclude that the widespread adoption of cover crops before spring‐sown crops will reduce overwinter drainage in UK Nitrate Vulnerable Zones by no more than c. 2%, compared with no cover before spring‐sown crops.