Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 10

Liczba wyników na stronie
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników

Wyniki wyszukiwania

help Sortuj według:

help Ogranicz wyniki do:
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
The Meghalaya Plateau, located in NE India, forms hilly horst block elevated to about 2000 m a.s.l. In the subtropical monsoonal climate, with strong mean annual rainfall gradient from 11,000 mm in Cherrapunji to 2,200 mm in Shillong and 1,600 mm in Gauhati were developed several cultivation systems. The shifting cultivation is the oldest and predominant system at lower elevations (such near Gauhati). It induces soil loss of about 40 t ha⁻¹ yr⁻¹ under cereals and perennial cropping on slopes up to 25-40°. As long as this system has long a cycle which permits forest regrowth on the abandoned fields, the effect of agricultural activity is not visible in the soil profiles. Intensive human activity (near Shillong), resulted in development of the sedentary agriculture, where soil erosion rates of about 55 t ha⁻¹ y⁻¹ are observed under potato cultivation. Radiocarbon dates of colluvial deposits in this area indicate intensification of agricultural human activity from at least 200-300 years. Closer to the southern margin of the plateau (near Cherrapunji), high monsoonal rainfall combined with cultivation in the past caused transformation of forest to grassland. The erosion below 2 t ha⁻¹ yr⁻¹ indicates that compact pavement of soil and root grass system has exerted a greater control over the sediment transfer than the energy impact of the rainfall and overland flow. Only wet rice cultivation in populated valleys and creation of terraces does not threat the environment. Various forms of agriculture and accelerated soil erosion lead to the gradual retreat of cultivated fields from high to low rainfall areas on the Meghalaya Plateau.
The estimation of soil erosion rates in complex tropical agricultural systems is difficult and most of the traditional methods have serious limitations. The ¹³⁷Cs technique allows to obtain relatively quickly retrospective medium term soil erosion results. The spatial variation of soil erosion rates was studied, in a small catchment under intensively cultivatcd fields and permanent grasslands on the hilly Meghalaya Plateau in India, using the ¹³⁷Cs technique. The measurcd values of cesium inventory for all sampling points are between 3% and 70% of the reference value of cesium inventory. The estimated annual soil loss depends strongly on the model used to calculation. It is visible that value obtained by simplified mass balance model (7.9-78.9 Mg·ha⁻¹·a⁻¹) and improved mass balance model (6.3-72.3 Mg·ha⁻¹·a⁻¹) are quite similar (whereas the value of soil erosion obtained by proportional model (5.6-18.1 Mg·ha⁻¹·a⁻¹) are far away from mass balance models. In case of grassland the diffusion-migration model was used and obtained results of soil erosion are lower than 0.5 Mg·ha·a⁻¹
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.