K+Ca2+ Ca2+ Ca2+

Ca2+

K+

K+Ca2+

K+ K+

Ca2+

K+

Ca2+

K+

K+

Dadan Mulyana Dept. Silvikultur Fakultas Kehutanan IPB

Definisi Kalium ditemukan pada tahun 1807 olehSir Humphrey Davy, yang dihasilkan dari potasy kaustik (KOH). Kalium merupakan logam pertama yang didapatkan melalui proses elektrolisis. Kalium mempunyai simbol K (Bahasa Latin: "Kalium" daripada bahasa Arab: "alqali") dan nombor atom 19

Potassium in Plants First or second in amount taken up bymost plants (N is usually first) Main functions Osmotic control Enzyme activation Deficiencies spotting, necrosis of leaf tips or edges, causes weak stems

K Deficiency

Corn

K DeficiencyAlfalfa

Soybean

Potassium Fertility K is most likely to be deficient underconditions of: Acid, weathered soils Sandy soils With high K-use crops (e.g. alfalfa) However, very high crop demand for K can sometimes create deficiencies in any soil

Cadangan K duniaDunia 1. Amerika utara 18.400 106tonK2O

2. amerika selatan3. eropa 4. russia 5. Afrika 6. Asia 7. Oseania Jumlah

165.723-9.400 24.000 141-150 544 Potensial 48.649-52.470

Cadangan K terbanyak > 24.000x106 tonK2O adalah di delta S.Mekong

Pentingnya K - K merupakan anggota unsur ke 3 (NPK)- Cadangan K sedikit - Kadar K di Indonesia tergolong rendah Teknologi tinggi untuk pengadaannya

Bentuk K tanah K berdasarkan ketersediaanya bagi tanaman dapat digolongkan : - Kalium relatif tidak tersedia- Kalium lambat tersedia - Kalium segera tersedia

Diagram hubungan ke tiga bentuk K adalah sbb. K-relatif tidak tersedia (feldspar, mika dll: 90-98%dari total K)

K-lambat tersedia K-tidak dapat dipertukarkan (l-10% dari K-total)

K-segera tersedia K-dapat dipertukarkan & K dalam larutan tanah (1-2 % K total)

90 %

10 %

K tidak dapat ditukar

K dapat ditukar

K-larutan tanah

Faktor yang mempengaruhi ketersediaan kaliumtipe koloid tipe 2:1 dapat fiksasi K, karena sifat mengembang dan mengerut tipe 1:1 tidak dapat fisasi Ksuhu t jumlah kalium dapat ditukar makin tinggi serapan K pembasahan dan pengeringan Kdd tanah kering kemasaman tanah fiksasi K pada pH tanah rendah, sehingga Kdd pelapukan pelapukan lanjut Kdd

Environmental Factors Affecting K Availability to a Plant 78 % of K

Soil moisture Low soil moisture results in more tortuous path for K diffusion takes longer to get to root Increasing K levels or soil moisture will increase K diffusion Increase soil moisture from 10 to 28 % can increase total K transport by up to 175 %

supplied to root via diffusion

Soil Aeration High moisture results in restricted root growth, low O2 and slowed K absorption by the root

Environmental Factors Affecting K Availability to a Plant Soil temperature Low temperature restricts plant growth and rate of K uptake Providing high K levels will increase K uptake at low temperatures

Soil pH At low pH, K has more competition for CEC sites As soils are limed, greater amount of K can be held on CEC and K leaching reduced.

Leaching K leaching can occur on course textured or muck soils particularly if irrigated

K Sources InorganicFertilizer Potassium chloride (muriate of potash) Potassium magnesium sulfate Chemical Formula KCl K2SO42MgSO4 Fertilizer Analysis 0-0-60 to 0-0-62 0-0-22 Salt Index 116 43

Potassium nitratePotassium sulfate

KNO3K2SO4

13-0-440-0-50

7446

Mineral Nitrat - niter Silikat - feldspar ortoklas sanidin mikroklin -feldspatoid losit -mika biotit moskovit Fosfat lukofosfit minyulit KNO3

Komposisi kimia

Kadar K2O (%) 46.5

K(AlSi308) K(AlSiO3.08) K(AlSi308) K(AlSi2O6) K(Mg, Fe)3 (AlS13 O10) KAI(AlSi3O10)(OH)2 K2 (FeAl)2(PO4)4(OH)116H2O KAl(PO4)2 (OH)31/2H2O

14.00 11.00 14.00 19-7.1 7.5 9.9

7.5 10.2

Neraca kaliumSisa hewan tanaman

Pupuk unorganik

Mineral Kalium

Air Irigasi

K-Tersedia

Terangkut tanaman

Tercuci

Tererosi

Fiksasi

Potassium in Soils Almost all soil K is in inorganic forms: Minerals K-feldspars Clays (often called fixed K): Primary micas (biotite, muscovite) Secondary clays (illite)

Exchangeable K+ on cation exchange sites

Available: K+ in soil solution

from PPI

Interlayer (fixed) K in Illite

K in soil claysPlanar position Inner position Hydrated and exchangeable cation Inner position

Edge position Hydroxy Al (or Fe) islands

Potassium in Clays The availability of K+ on clays to plantsdepends on position on the clay (micas, illite): inner sites - low availability, fixed K in illite edge sites - moderate availability planar sites - high availability readily exchangeable

Potassium Equilibrium in SoilsSoln. K+ Solution Exch. K+ planar sites edge sites Fixed K+ inner sites Mineral K+ feldspars

K in solution is usually K pada tanah masamK tidak begitu kuat diretensi. Titik jerapan akan dimenangkan oleh Al sehingga K lepas Antara K dan Ca K dapat menggantikan Ca dari jerapan liat. Kalau tanah didominasi Ca (kapur), maka pada tanah itu ada peluang besar akan terjadi retensi K lebih banyak pada liat

b. NH4+,Dapat menghalangi pembebasan K yang terikat, karena NH4+ terikat seperti K. Ini terjadi pada ilit atau vermikulit

NH4 ditambahkan Mg/100gr 0 10 25 50 100

K TDD diserap jagung Mg/K 22 16 12 5 1

Makin banyak NH4+ ditambahkan makin sedikit K TDD diserap

Add a solution of ammonium acetateNH4+ NH4+ NH4+ NH4+ NH4+ NH4+ NH4+ NH4+ NH4+ NH4+ NH4+ NH4+ + NH4 NH4+ NH4+ NH4+ NH4+ NH4+ NH4+

Note: Ammonium acetate extraction will remove only the K+ on planar and edge exchange sites, and K+ in solution.

NH4+NH4+ NH4+

NH4+

NH4+

K+Ca2+ Ca2+ Ca2+

Ca2+

NH4+

NH4+

K+

NH4+

NH4+ NH4+

NH4+

NH4+

K+Ca2+

K+ K+

Ca2+

K+NH4+

NH4+

NH4+

NH4+

Ca2+

NH4+

NH4+

NH4+

K+

K+

Soil with exchangeable cationsCa2+ K+

Measure amount of K+ released

Kdd hilang oleh pencucian 100 80 60 40 20

4,5

5,5

6,5

pH tanah

Gambar : Hubungan kehilangan Kdd dengan pH tanah

Tips for Managing K Soil test first!!! Many soils dont need K. K loss is not usually a problem in mostsoils, except very sandy soils. K does not cause environmental problems. Beware of K-fixing soils! K can be applied significantly in advance of plant needs, because of the low risk of loss.