Siklus NPK

SIKLUS NITROGEN SIKLUS NITROGEN

Siklus hara adalah pergerakan unsur/hara pada Siklus hara adalah pergerakan unsur/hara pada suatu sistem suatu sistem

Pergerakan siklus hara memerlukan sumber Pergerakan siklus hara memerlukan sumber energi -------- sumber energi (sinar matahari) energi -------- sumber energi (sinar matahari)

The Nitrogen CycleThe Nitrogen Cycle

Four processes participate in the cycling of Four processes participate in the cycling of nitrogen through the biosphere: nitrogen through the biosphere:

nitrogen fixation decay nitrification nitrification denitrificationdenitrification Microorganisms play major roles in all four of Microorganisms play major roles in all four of

these. these.

Symbiotic nitrogen fixationSymbiotic nitrogen fixation 1. Legume symbioses1. Legume symbioses The most familiar examples of nitrogen-fixing symbioses are the The most familiar examples of nitrogen-fixing symbioses are the root nodules of root nodules of

legumeslegumes (Paraserianthes falcataria, Accacia spp, peas, beans, clover, etc.). (Paraserianthes falcataria, Accacia spp, peas, beans, clover, etc.).

Part of a crushed root nodule of a pea plant, showing four root cells Part of a crushed root nodule of a pea plant, showing four root cells containing colonies of containing colonies of RhizobiumRhizobium. The nuclei (. The nuclei (nn) of two root cells are ) of two root cells are shown; shown; cwcw indicates the cell wall that separates two plant cells. Although it indicates the cell wall that separates two plant cells. Although it cannot be seen clearly in this image, the bacteria occur in clusters which cannot be seen clearly in this image, the bacteria occur in clusters which are enclosed in membranes, separating them from the cytoplasm of the are enclosed in membranes, separating them from the cytoplasm of the plant cells. plant cells.

In nodules where nitrogen-fixation is occurring, the plant tissues contain In nodules where nitrogen-fixation is occurring, the plant tissues contain the oxygen-scavenging molecule, the oxygen-scavenging molecule, leghaemoglobinleghaemoglobin (serving the same (serving the same function as the oxygen-carrying haemoglobin in blood). The function of function as the oxygen-carrying haemoglobin in blood). The function of this molecule in nodules is to reduce the amount of free oxygen, and this molecule in nodules is to reduce the amount of free oxygen, and thereby to protect the nitrogen-fixing enzyme thereby to protect the nitrogen-fixing enzyme nitrogenasenitrogenase, which is , which is irreversibly inactivated by oxygenirreversibly inactivated by oxygen

2. Associations with 2. Associations with FrankiaFrankia 2. Associations with 2. Associations with FrankiaFrankia

Frankia Frankia is a genus of the bacterial group termed is a genus of the bacterial group termed actinomycetesactinomycetes - - filamentous bacteria that are noted for their production of air-borne spores. filamentous bacteria that are noted for their production of air-borne spores. Included in this group are the common soil-dwelling Included in this group are the common soil-dwelling StreptomycesStreptomyces species species which produce many of the antibiotics used in medicine (see which produce many of the antibiotics used in medicine (see StreptomycesStreptomyces). ). FrankiaFrankia species are slow-growing in culture, and require species are slow-growing in culture, and require specialised media, suggesting that they are specialised symbionts. They specialised media, suggesting that they are specialised symbionts. They form nitrogen-fixing root nodules (sometimes called actinorhizae) with form nitrogen-fixing root nodules (sometimes called actinorhizae) with several woody plants of different families, such as alder (several woody plants of different families, such as alder (AlnusAlnus species), species), sea buckthorn (sea buckthorn (Hippophae rhamnoidesHippophae rhamnoides, which is common in sand-dune , which is common in sand-dune environments) and environments) and CasuarinaCasuarina (a Mediterranean tree genus). Figure A (a Mediterranean tree genus). Figure A (below) shows a young alder tree ((below) shows a young alder tree (Alnus glutinosaAlnus glutinosa) growing in a plant pot, ) growing in a plant pot, and Figure B shows part of the root system of this tree, bearing the orange-and Figure B shows part of the root system of this tree, bearing the orange-yellow coloured nodules (arrowheads) containing yellow coloured nodules (arrowheads) containing Frankia.Frankia.

3. Cyanobacterial associations3. Cyanobacterial associations

The photosynthetic cyanobacteria often live as free-living organisms in The photosynthetic cyanobacteria often live as free-living organisms in pioneer habitats such as desert soils (see cyanobacteria) or as symbionts pioneer habitats such as desert soils (see cyanobacteria) or as symbionts with lichens in other pioneer habitats. They also form symbiotic with lichens in other pioneer habitats. They also form symbiotic associations with other organisms such as the water fern associations with other organisms such as the water fern AzollaAzolla, and , and cycads.The association with cycads.The association with AzollaAzolla, where cyanobacteria (, where cyanobacteria (Anabaena Anabaena azollaeazollae) are harboured in the leaves, has sometimes been shown to be ) are harboured in the leaves, has sometimes been shown to be important for nitrogen inputs in rice paddies, especially if the fern is important for nitrogen inputs in rice paddies, especially if the fern is allowed to grow and then ploughed into the soil to release nitrogen before allowed to grow and then ploughed into the soil to release nitrogen before the rice crop is sown. A symbiotic association of cyanobacteria with the rice crop is sown. A symbiotic association of cyanobacteria with cycads is shown below. The first image shows a pot-grown plant. The cycads is shown below. The first image shows a pot-grown plant. The second image shows a close-up of the soil surface in this pot. Short, club-second image shows a close-up of the soil surface in this pot. Short, club-shaped, branching roots have grown into the aerial environment. These shaped, branching roots have grown into the aerial environment. These aerial roots contain a nitrogen-fixing cyanobacterial symbiont.aerial roots contain a nitrogen-fixing cyanobacterial symbiont.

Organisme membutuhkan fosfor untuk banyak Organisme membutuhkan fosfor untuk banyak hal.hal.

Daur fosfor lebih sederhana daripada daur-daur Daur fosfor lebih sederhana daripada daur-daur lainnya karena daur fosfor tidak melibatkan lainnya karena daur fosfor tidak melibatkan atmosfer.atmosfer. Fosfor hanya ada dalam bentuk fosfat, yang diserap Fosfor hanya ada dalam bentuk fosfat, yang diserap

tanaman dan digunakan untuk sintesis senyawa tanaman dan digunakan untuk sintesis senyawa organik.organik.

Humus dan partikel tanah mengikat fosfat, hal Humus dan partikel tanah mengikat fosfat, hal ini menyebabkan daur fosfat bersifat lokal.ini menyebabkan daur fosfat bersifat lokal.

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Daur FosforDaur Fosfor

+

Daur FosforDaur Fosfor Sumber utamaSumber utama

batuanbatuan Bahan organik Bahan organik

tanahtanah tanamantanaman POPO44

-- dalam dalam tanahtanah

Input:Input: pelapukan batuanpelapukan batuan

Output:Output: fiksasi mineral, fiksasi mineral, pelindianpelindian

Daur N dan PDaur N dan P Titik perhatianTitik perhatian::

ketersediaan sebagai faktor ketersediaan sebagai faktor pembataspembatas

dekomposisi membatasi dekomposisi membatasi ketersediaanketersediaan

Proses berjangka panjang

Proses berjangka pendek

1

2

Havlin et al., 2001Havlin et al., 2001

Potassium CyclePotassium Cycle

The Potassium CycleThe Potassium CycleAnimal

manuresand biosolids

Mineralfertilizers

Crop harvest

Runoff anderosion

Leaching

Soil solution potassium (K+)

Plant residues

Plantuptake

Mineralpotassium

Fixedpotassium

Exchangeable potassium

Input to soilComponent Loss from soil

K release during mineral K release during mineral weatheringweathering

Recolored from Fig. 6.9 in Havlin et al. (1999)

Exchangeable vs. Exchangeable vs. Non-exchangeable KNon-exchangeable K

Exchangeable KReadily buffers soil solution K

Non-Exchangeable KSlowly buffers soil solution K

Soil tests measure exchangeable K