HUBUNGAN TANAH, AIR DAN

TANAMAN

Batasan Tanah dari sudut ekologi Tumbuhan

Komponen penyusun tanah dan perannya bagipertumbuhan dan produksi tanaman

Profil Tanah dan pengaruhnya terhadap vegetasi

Faktor yang mempengaruhi sifat tanah

Sifat fisika, kimia, biologi, hidrologi danmorfologi tanah

Faktor yang berpengaruh terhadap hasil tanaman

Tanah? akumulasi tubuh alam bebas,

berdimensi tiga,

menduduki sebagaian besar permukaan

daratan bumi, yang

mampu menumbuhkan tanaman, dan

memiliki sifat sebagai pengaruh iklim (I) dan

organisme (O) yang bertindak terhadap

bahan induk (B) pada kondisi topografi (L)

tertentu dan selama waktu (W) tertentu”

(Donahue, 1970).

GAS

CAIRAN /

LIQUID

PADATAN /

SOLID

RUANG PORI

(VOID)

MINERAL LEMPUNG

BAHAN ORGANIK

RUANG PORI

(VOID)

BAHAN ORGANIK

20- 30%

20- 30%

< 5%

45% MINERAL LEMPUNG

Tanah Pertanian Ideal

Tanah yang baik untuk pertumbuhan

tanaman darat non padi: tersusun

atas komponen

• bahan mineral 45%,

• bahan organik 5%,

• udara 20-30% dan air 20-30%

• (atas dasar volume).

Media

Tumbuh

Tanah

BahanOrganik

AIR

Hara

SifatFisik

SifatKimia

• KompleksPertukaran

• Nutrisi

Biologi• Mikroorganisme

• Dekomposer

SIFAT FISIKA TANAH

• Tektur• Pori• Struktur

TEKTUR TANAH

Faktor penentu tekstur tanah?

Mengapa tekstur tanah penting?

Particle sizes:

• Gravel: >2.0 mm

• Sand: 0.05-2.0 mm

• Silt: 0.002-0.05 mm

• Clay: <0.002 mm (microscopic)

Fig

. 6.7

, C

am

pbell

& R

eece,

7th

ed.

Pengaruh ukuran partikel pada permukaan :volume ratio

Importance of soil particle size—

Critical in determining soil physical properties.

Clay has much higher surface:volume ratios (due to small particle size) than larger particles.

Electrostatically negative charges on clay micellespermit stronger adsorption of water and nutrients, reducing leaching, especially of cationic nutrients (e.g., NH4, Ca, Mg, K, Na, Cu, Mn, Zn, Fe all have + charges)

Too much clay results in reduced pore sizes

Sand—with its larger particle sizes—has characteristics opposite to those of clay

Silt is between clay and sand in size and traits

Best agricultural soils are classed as loams, varying broadly around a 40:40:20 ratio of sand, silt, and clay, respectively

SIFAT KIMIA TANAH

• Macronutrients• micronutrients• Pertukaran ion

Macronutrients—

Macronutrients are defined as elements that make up >0.1% of plant tissue dry weight

C, H, and O—the basic constituents of organic molecules—make up about 96% of plant dry weight.

Other macronutrients include N, P, K, Ca, S, Mg

Macronutrients—

Their functions

Ta

ble

6.1

, S

mith &

Sm

ith 7

thed. (p

. 120

)

Micronutrients—

Micronutrients (a.k.a., “trace elements”) are needed in small quantities (<0.01% by weight)

Although required in tiny amounts, micronutrients are nonetheless essential

Often serve as cofactors, facilitating enzyme activity

E.g., Cu, Mn, Zn, Fe

Using hydroponic culture to identify essential plant nutrients

Fig

. 37.2

, C

am

pbell

& R

eece (

6th

ed)

Identifying essential plant nutrients—

Magnesium deficiency in a tomato plant

Fig. 37.3, Campbell & Reece (6th ed)

Gas exchange and the uptake of water and nutrients by a plant: an overview

Fig

. 37.1

, C

am

pbell

& R

eece (

6th

ed)

Cation exchange capacity (CEC) of soil—

Capacity of the soil to adsorb cations

Strength of cation retention depends on number of “exchange sites” and the intensity of the charges on them.

Largely determined by clay and humus content

Clay micelles have numerous negative charges. Because of the tiny size of the clay particles and the resulting small soil pore sizes, clayey soils tend to a high CEC.

Plant roots use cation exchange to assist in nutrient uptake from the soil—

(a) Soil moisture surrounding the roots

(b) Absorption of soil mineral nutrients by cation exchange

Where does the plant get this CO2 that it’s putting into the soil??

Fig. 37.6, Campbell & Reece (6th ed)

Fig. 4.11, Smith & Smith 7th ed. (p. 66)

Absorption and leaching of soil nutrients in the soil solution

Soil moisture and water uptake by plants—

Water moves in response to a gradient of water potential, from higher water potential to lower water potential.

Net water potential in the plant is determined by

(a) osmotic pressure—due to cross-membrane differences in solute concentration,

(b) water pressure—due to atmospheric pressure, and

(c) the transpiration stream—which pulls water up through xylem tissues, based on transpiration from leaves and the adhesion and cohesion properties of water.

Fig. 6.3, Smith & Smith (5th ed), p. 105

Water movement through a plant—

the “transpiration stream”

A stoma functions in gas exchange—

Stomatal openings respond to environmental cues to control gas exchange rates—

Fig. 36.14, Campbell & Reece, 7th ed. (p. 749)

Open Closed

The water balance of living cells

Fig. 8.12, Campbell & Reece (6th ed)

A wilted tomato plant regains its turgor when watered

Fig. 36.5, Campbell & Reece (6th ed)

Fungsi-fungsi Tanah Sebagai

Sumberdaya Alam

unsur produksi pertanian

unsur pengatur tata air siklus hidrologi

unsur perlindungan alam/lingkungan

unsur teknik bangunan/infrastruktur

• Mendukung aktivitas biologi, keaneka ragaman hayatidan produktivitas

• Mengatur tata air dan aliran lautan

• Sebagai saringan, buffer, degradator, detoksifikatorsenyawa anorganik dan organik, termasuk limbahindustri, rumah tangga dan limbah atmosfer;

• Menyimpan dan mendaur ulang hara dan unsur lain didalam biosfer;

• Mendukung bangunan dan melindungi kekayaanarkeologi.

Fungsi-fungsi Tanah

(Karlen et al., 1997)

Hidrologi adalah ilmu yang berhubungan dengan kejadian,

pergerakan dan distribusi air di dalam Siklus Hidrologi.

Siklus Hidrologi adalah dinamika sistem transfer air alami

dimana air secara kontinyu bergerak dan berubah dari satu

bentuk ke bentuk yang lain, dan selama itu jumlah total air

di bumi tetap.

Walaupun menurut definisi, hidrologi mencakup studi air tanah,dalam aplikasinya penekanan hidrologi masih terfokus padastudi aliran air di permukaan dan faktor-faktor sejenis yangmenentukan

Studi tentang aspek-aspek kejadian dan pergerakan air tanahdilakukan secara terpisah dan umumnya dikenal sebagaiGeohydrology (Hidrologi air tanah – groundwater hydrology)

Hydrologic Cycle

Water enters the soil, interacts with soil particles and leaves the soil (through

evaporation, transpiration or leaching).

Setelah mencapai permukaan bumi, air hujan terus bergerak danberubah bentuknya, yaitu:

bagian yang masuk ke dalam tanah – Infiltration,bagian yang mengalir sepanjang permukaan – Run-off, bagian yang kembali ke atmosfer sebgai uap air – Evaporation, bagian yang diambil tanaman dan dikembalikan ke atmosfer –Transpiration.

Bagian air hujan yang ditangkap oleh daun dan batang tanaman disebut Interception.

Bagian air hujan yang terkumpul di permukaan tanah disebut Surface Storage,

Bagian air hujan yang diikat di dalam tanah– Soil moisture danbagian yang diperkolasikan ke bagian bawah tanah yangberhubungan dengan zone jenuh air – Groundwater, sehinggasecara sederhana neraca air dapat ditulis sebagai:

Precipitation = Runoff + Evapo-transpiration + Change storage

Hydrologic Cycle and the Soil

Color

Structure

Bulk Density

Texture

pH

Temperature

Moisture

Horizon

Depths

Soil Properties that are part of the hydrologic cycle.

SIKLUS HIDROLOGI HUJAN

Hujan

Hujan lebih Intersepsi Evp & Ept, dll.

Infiltrasi

SSRO Perkolasi dalam

PromptSSRO

Delayed SSRO

Groundwater storage

Direct RO Base flow

Aliran permukaan

Total RO/Stream flow

Fungsi Tanah sebagai

Faktor Produksi Tanaman

• Tunjangan mekanis sebagai tempat tanaman tegak dan tumbuh;

• Penyedia air, udara dan unsur hara (nutrisi);

• Lingkungan tempat akar atau batang dalam tanah melakukan aktivitas fisiologinya

• Pengontrol temperatur tanah

• Tempat tumbuh dan berkembangnya organisme tanah.

TERIMA KASIH