The composition of the leachate through cropped and uncropped soils in lysimeters compared with that of the rain

Abstract

SUMMARYThe composition of the leachate from undisturbed monolith lysimeters cropped with white clover or meadow fescue or maintained bare was compared with t h a t of the rain falling on rhein. No nitrogen fertilizer was applied only an initial dressing of phosphorus and potassium. The grass received rauch more nitrogen from the rain than it lost by leaching whereas the clover lost more t h a n it received. Most of the leached Ilitrogen was N O s -N -92 per cent on the bare soil and 90 per cent on the clover. A b o u t 271b nitrogen per acre (30 kg/ha) per year was drained from the actively growing clover sward risilig to about 1171b N/acre/year (131 kg/ha) when the clover died or was removed. Only 2.31b/ac (2.5 kg/ha) was drained from the actively growing grass sward. I t was estimated t h a t the clover fixed at least 2701b N/ac/year (303 kg/ha/year. The rates of leaching of potassium from a grass sward was about 1.7 lb/ac/year (1.9 kg/ha) and 0.8 lb (0.9 kg) phosphorus. The quantities were similar for clover. The grass received from the rain more phosphorus and potassium than was leached but only 60 per celit of the calcium and 13 per cent of the magnesium, similar results being obtained with white clover.During the year of establishment of the grass sward there was evidence of loss of gaseous nitrogen (elemental alid/or compoulld) from the soll: subsequently the nitrogen content of the soil slowly increased. Calcium loss from the bare soil with all average rainfall of 26" (650 mm) was about 100 Ib Ca/ac/year ( 112 kg/ha).

Direct field measurements of leaching losses of nitrogen in pasture and cropping soils using tension lysimeters

“…However, under pasture, leaching losses of soil N (Table 1) are considerably higher than those reported in the literature. This is in contrast to earlier conclusions based on results from monolith and filled-in lysimeter studies (Karraker et al 1950;Theron 1964;Low & Armitage 1970) and periodical analyses of inorganic N levels at various soil depths (Cunningham & Cooke 1958;Gasser 1959;Tham 1971;Risk 1976).…”

“…These lysimeters have larger cross-sectional areas than porous tubes or cups and therefore they are more likely to reduce sampling errors, especially in the composition of the leachate collected (van der Ploeg & Besse 1977). Furthermore, the installation of tension lysimeters causes little distortion of soil structure and the plant rooting system compared with installing various kinds of classical lysimeters, whose relative merits have been discussed extensively by Low & Armitage (1970).…”

Effects of sward botanical composition on nitrogen and potassium leaching in cut grassland

“…The corresponding figures in the grass-clover sward were 16.7 (1 st year), 19.8 (2 nd year) and 21.0 (3 rd year) mg L -1 N, and in the grass-only sward 15.9 (1 st year), 17.5 (2 nd year) and 19.7 (3 rd year) mg L -1 N. Significant difference between two swards appeared in the second year; probably it was due to the decrease in legume content in the sward (Table 5) and the decomposition of N-rich plant residues in the soil. Earlier Low and Armitage (1970) studies have demonstrated increased leaching in the swards with reduced legume content.…”

“…Eriksen et al (2004) have reported that less leaching occurs from unfertilized grassland containing white clover than from fertilized grass-only grassland. Low and Armitage (1970) studies have demonstrated increased leaching in the swards with reduced legume content.…”

An elementary model of nitrogen uptake and redistribution by annual plant species

“…Nitrogen concentration of rainfall varies widely but is generally between 1 to 2.5 ppm (Low and Armitage, 1970). As it becomes available during the season (unlike fertilizer nitrogen which is immediately available at the beginning) it may -·· bSl_of cQnsiderikblej:rnp_ortancejn maintaining_ growth towards th~e_e,._,n""'d~o""'f"'----"t~h~e _____ _ season.…”