Nutrient sources in four forest watersheds in Japan: the contribution of precipitation, weathering and litter fall

<p>Base cation such as calcium and potassium is important nutrient for tree growth in forest ecosystems.  Major sources of basic cation to forest soil are precipitation, weathering of parent material and litter fall.  Weathering rate of basic cation is estimated from the input from precipitation, runoff from stream and uptake by vegetation.  Nutrient cycling of many Japanese forest ecosystems has been studied but information about the contribution of these sources is limited.  This study compared three nutrient sources in four forest watersheds in Japan.  These are Oyasan (Gunma Pref.), Kamikamo (Kyoto Pref.), Kiryu (Shiga pref.) and Takatori (Kochi Pref.).  We calculated nutrient budget of potassium, calcium and magnesium.  The rate of rock weathering of base cation ranged from 0.22 to 4.37 kmolc ha<sup>-1</sup> yr<sup>-1</sup> and increased in the order of Kamigamo < Kiryu < Oyasan < Takatori.  In potassium cycling, the contribution of litter fall was greater than that of weathering or precipitation.  The runoff of calcium and magnesium from soil was greater in Takatori, where the rate of weathering was high.  Although the rate of weathering varied substantially among forest watersheds, the annual flux of litter fall was relatively constant.  Similar calculation was applied for nitrogen cycling and the　source from soil was treated as that from nitrogen accumulated during the past pedogenesis.  Nitrogen input from the accumulated soil source was 36 % in Oyasan whereas that in other three watersheds was 0%. Oyasan was considered as a nitrogen-saturated forest and the result of the study suggest the ecosystem relies on different nitrogen source.</p>

THE INFLUENCE OF MULTI-YEAR ORGANIC AND MINERAL FERTILISATION ON THE PHYSICOCHEMICAL PROPERTIES OF LESSIVE SOIL

<p>In a multi-year field fertilisation experiment the effects of organic and mineral fertilisers on the physicochemical properties of lessive soil were compared. Manure, two doses of slurry and mineral fertilisers were applied to soil farmed in an eight-field crop rotation. Dose 1 of slurry, manure and mineral fertiliser were applied in doses balanced with nitrogen. Dose II of slurry was determined so that the amount of organic carbon introduced along with it was the same as in the dose of manure. To the experimental facilities with manure and slurry, additional fertilisation with phosphorus and potassium was applied. Following 36 years of annual fertilisation, samples of soil were taken from the 0-25 cm layer, determining the amount of organic carbon and the sorption properties of the soil. It was determined that as a result of applying organic fertilisers, the amount of organic carbon, sorption complex capacity and basic cation content increased whereas hydrolytic acidity decreased. Manure was found to have the most beneficial effect, which was matched by neither dose I nor II of slurry. Additional phosphorus-potassium fertilisation of soil with manure and slurry positively influenced the sum of bases and the total sorption capacity of the soil. Mineral NPK fertilisation led to the decrease in the saturation of bases of the sorption complex and the increase in hydrolytic acidity.</p><p> </p><p>W wieloletnim polowym doświadczeniu nawozowym porównano działanie nawozów naturalnych i mineralnych na właściwości fizykochemiczne gleby płowej. Pod rośliny uprawiane w 8-polowym zmianowaniu stosowano obornik, gnojowicę w dwóch dawkach i nawozy mineralne. Gnojowicę w dawce I, obornik i nawożenie mineralne stosowano w dawkach zrównoważonych azotem. Wielkość dawki II gnojowicy określono tak, by ilość wprowadzanego z nią węgla organicznego była taka sama jak w dawce obornika. W obiektach z obornikiem i gnojowicą stosowano dodatkowe nawożenie fosforem i potasem. Po 36 latach corocznego nawożenia pobrano próbki gleby z warstwy 0-25 cm i oznaczono zawartość węgla organicznego oraz właściwości sorpcyjne gleby. Stwierdzono, że w wyniku stosowania nawozów organicznych wzrosła zawartość węgla organicznego, pojemność kompleksu sorpcyjnego i zawartość kationów zasadowych, a zmalała kwasowość hydrolityczna. Najkorzystniej na badane właściwości gleby działał obornik, któremu ustępowała gnojowica w dawce II i gnojowica w dawce I. Dodatkowe nawożenie fosforowo-potasowe w obiektach z obornikiem i gnojowicą działało korzystnie na sumę zasad i całkowitą pojemność sorpcyjną gleby Nawożenie mineralne NPK spowodowało zmniejszenie wysycenia kompleksu sorpcyjnego zasadami i wzrost kwasowości hydrolitycznej.<br /><br /></p>