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The relationship between soil structure, soil cultivation, nitrogen uptake, and crop growth. II. —Effects of Cultivation on Aggregation of Soil
Author(s) -
Singh Khazan,
Pollard A. G.
Publication year - 1956
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.2740070802
Subject(s) - plough , agronomy , nitrogen , soil horizon , soil water , organic matter , crop , chemistry , field experiment , tine , soil structure , soil science , environmental science , biology , organic chemistry , structural engineering , engineering
The effects of depth of cultivation on aggregation of the Harlington field station soil, during 1949 and 1950, are examined, the crops studied being swedes in 1949 and spring wheat in 1950. The type of cultivation influenced the size distribution of aggregates, mainly in the surface 4 in. of soil. The larger aggregates >0 ·5 mm., particularly those of 4–2 mm. diam., were more especially affected. Both deep‐ and shallow‐ploughed plots contained a higher percentage of larger aggregates > 0·5 mm. than did the tine‐cultivated plots. The plough by inverting the slice brought the better structured sub‐surface soil to the surface and thus increased the percentage of larger aggregates >0·5 mm. in the 0–4‐in. layer. This effect of ploughing lasted for abouut 4 to 5 months. Except in one instance, the type of cultivation did not affect the ‘degree’ of aggregation of particles <0·05 mm.; both deep‐ and shallow‐ploughed soils showed a greater degree of aggregation than did the tine‐cultivated soil. With all three types of cultivation the horizon A 1 of the soil contained a higher proportion of larger aggregates >1· 0 mm. than did horizon A 2 . The reverse was true of the smaller aggregates <1·0 mm., particularly those of 0·25–0·05 mm. diam. Differences between the proportion of very fine particles (<0·5 mm.) in the two horizons were small. The higher content of clay and lower content of organic matter in horizon A 2 than in horizon A 1 were probable factors in these differences. Seasonal variations were apparent in both the size distribution of aggregates and the degree of aggregation of soil during two years. Soil moisture played the major part in these variations, lower moisture content being associated with higher content of aggregates >0·05 mm. and vice versa. Disruption of aggregates occurred throughout the two growing seasons, which demonstrates the unstable nature of the structure of this soil. The order of stability among aggregates of different sizes was 0·25–0·05, 0·5–0·25, 2·0–1·0 mm. > 1·0–0·5 mm. > 4·0–2·0 mm. ≫ 4·0 mm., and that among individual layers in the soil profile was: 0–2‐in., 8–12‐in. layers < 2–4‐in., 4–8‐in. layers. Seasonal variation in the stability of the aggregates was in the order: August > September, January > October, July. No significant differences existed between the cultivation treatments in regard to disruption of aggregates or in their stability. No experimental evidence was obtained that finer material (particles <0·05 mm.) became leached from the upper to lower depths.