MK. MANAJEMEN KESUBURAN TANAH

MANAJEMEN PEMUPUKAN YANG

RAMAH-LINGKUNGAN

Smno.jurtnh.fpub.2013

PENGELOLAAN HARA TANAH..

..

Tujuan pengelolaan hara tanah adalah menghasilkan tanaman yang menguntungkan secara berkelanjutan. Hal ini berarti bahwa faktor-faktor seperti biaya (amandemen, bahan bakar, dan peralatan) harus dievaluasi

kontribusinya terhadap peningkatan hasil tanaman. Misalnya, penambahan dua kali jumlah pupuk mungkin tidak meningkatkan hasil

panen dua kali lipat. Dengan demikian, petani harus menentukan apakah biaya tambahan pupuk dapat dilunasi oleh tambahan hasil panen.

Selain itu, petani harus selalu berpikir “bahwa praktik pengelolaan yang tidak memadai atau berlebihan dapat mempengaruhi kualitas tanah dari

waktu ke waktu”. Salah satu penyebab utama erosi atau kehilangan tanah adalah karena kerusakan struktur tanah, yang dapat disebabkan oleh praktek-praktek seperti pengolahan intensif (pengolahan tanah), lalu

lintas kendaraan di atas permukaan tanah secara berlebihan, pengambilan secara berlebihan residu tanaman, dan pengurasan hara

tanah, terutama nitrogen.

UNSUR HARA

Ada sekitar 14 unsur esensial yg diperoleh tanaman dari tanahCa dan Mg diberikan ke tanah berbentuk kapur.Unsur hara makro yg paling sering bermasalah adalah N, P, KKetiga unsur hara ini lazim disebut sebagai UNSUR PUPUK

KESEIMBANGAN HARA Unsur hara N, P, K bila dipakai secara tepat, akan mampu mengendalikan, mengimbangi, mendukung dan mengisi satu-sama-lain, serta berpengaruh baik thd unsur hara lainnya. Unsur hara pupuk yg diberikan seyogyanya merupakan tambahan bagi unsur yg sudah ada dalam tanah, sehingga keseimbangan hara tanah dapat menunjang pertumbuhan tanaman yg baik.

TIGA KELOMPOK BAHAN PUPUK1. Pembawa nitrogen2. Pembawa fosfat tersedia3. Pembawa kalium larut air.

PEMBAWA NITROGEN

Pupuk N juga disebut dengan istilah AMONIAT, ada dua kelompok, yaitu:1. ORGANIK2. ANORGANIK

PEMBAWA NITROGEN ORGANIKPupuk organik harus mengalami aminisasi, amonifikasi, dan nitrifikasi sebelum nitrogennya tersedia bagi tanaman.Pupuk organik secara lambat dan berangsur-angsur membebaskan nitrogen sepanjang musim tanaman.

Pupuk organik Sumber Persentase N

Darah kering Rumah Potong Hewan 8 - 12Sisa daging RPH 5 -10 (3-13% P2O5) Tepung daging RPH 10-11 (1-5% P2O5)Sisa ikan kering Pengolahan ikan 6 - 10 (4-8% P2O5)Tepung biji kapas Ampas 6-9 (2-3% P2O5; 1-2% K2O)Batang tembakau Sisa 1.5 - 3.5 (4-9% K2O)Tepung tembakau Ampas 5 - 7 (2% P2O5, 1% K2O)Tepung coklat Ampas 3.5 - 4.5Sekam padi Ampas 1.0

Sumber: Nelson, 1965

PEMBAWA NITROGEN

ANORGANIK

Pertimbangan Umum:Pupuk N anorganik dapat dibuat dari N2 atmosfer

dengan teknologi sintetik yang semakin maju.

Pupuk Rumus Kimia Persentase Nitrogen

Natrium nitrat NaNO3 16Ammonium sulfat (NH4)2SO4 21Amonium nitrat NH4NO3 33Amonium nitrat gamping NH4NO3 dan dolomit 20Urea CO(NH2)2 42 - 45Kalsium sianamida CaCN2 22Amonia cair NH3 cair 82Larutan amonia NH4OH encer 20-25Amofos NH4H2PO4 11 (48% P2O5)Diamonium fosfat (NH4)2HPO4 21(53% P2O5)

AMONIA

NH3

Gas amonia dibuat dari unsur-unsurnya, Hidrogen dan nitrogen:

N2 + 3H2 ------------------------ 2 NH3

Penggunaannya:1. Dg menggunakan tekanan tinggi dapat dicairkan menjadi

amonia cair2. Dapat dilarutkan dlm air menjadi NH4OH3. Gas amonia dipakai untuk pembuatan pupuk lain

Bagan pembuatan pupuk Nitrogen: + NH3 Am. Nitrat 33% N

HNO3 Na2CO3 Na-nitrat 16% N + Batu fosfat Nitrofosfat 12- 20% N

+O2+ H2SO4 Am. Sulfat 21% N

NH3 + H3PO4 Am. Fosfat 11-21% N

+ CO2 Urea 45% N

+NH4NO3, +Urea, + H2O Larutan N 27-53% N

+ H2O Larutan amonia 20% N

PUPUK NITROGEN

AMONIUM SULFATBanyak digunakan oleh petani di IndoensiaDapat digunakan untuk membuat pupuk majemukIon NH4+ dalam kondisi aerobik dapat mengalami nitrifikasiPada sawah NH4+ bereaksi dengan koloid tanah, shg tdk tercuciPada tanah alkalis memberikan hasil yang memuaskan

Natrium & AMONIUM NITRATAmonium nitrat mengandung ion NH4+ dan NO3- Pemberiannya sebaiknya dlm bentuk pelet, unt mengurangi sifat higroskopisMUDAH MELEDAK BILA TERJADI KEBAKARAN

UREA Reaksi pembuatannya: 2NH3 + CO2 NH2COONH4 NH2CONH2 + H2O

PUPUK FOSFAT

SUPERFOSFATKandungan fosfatnya 16-21%, dibuat dengan jalan menambahkan asam sulfat kepada batu fosfat.

Ca3(PO4)2 + 2H2SO4 Ca(H2PO4)2 + 2CaSO4 + kotoranCaHPO4

Superfosfat biasa( 20% P2O5)

+ H2SO4 Pupuk majemuk

Batu +H2SO4 or H3PO4 +NH3 NH4-fosfat (20-54% P2O5) Fosfat tanur listrik 54% P2O5

TSP (42-50% P2O5)

+ HNO3 + NH3 Nitrofosfat (11-35% P2O5)

PUPUK FOSFAT

SP : Super PhosphateTSP : Triple Super Phosphate

Pupuk Bentuk Kimiawi Kadar P2O5 tersedia (%) Persen P

Superfosfat Ca(H2PO4)2 + CaHPO4 15-50 7 - 22

Superfosfat NH4H2PO4 amoniat CaHPO4

Ca3(PO4)2 16-18 (3-4%N) 7 - 8(NH4)2SO4

Amofos NH4H2PO4 48 (11% N) 21

Amonium-polifosfat (NH4)4P2O7 & lainnya 58-60 (12-15%N) 26-27

Diamonium fosfat (NH4)2HPO4 53 (21% N) 23

Sampah tanur baja (CaO)5.P2O5.SiO2 15-25 7-11

Batu fosfat Fluor atau Klor Apatit 25-30 11 - 13Ca-metafosfat Ca(PO4)2 62-63 27-28Asam superfosfat H3PO4 dan H4P2O7 76 33

Klasifikasi Pupuk Fosfat

Pupuk fosfat dapat diklasifikasikan berdasarkan ketersediaan fosfatnya. FOSFAT TERSEDIA: Fosfat yang segera dapat diserap tanaman dan merangsang pertumbuhan tanaman

KLASIFIKASI PUPUK FOSFAT

1. Larut dalam air Ca(H2PO4)2

NH4 H2PO4

K H2PO4 Fosfat tersedia2. Larut dlm sitrat: 15% amonium sitrat CaHPO4

atau 2% asam sitrat

3. Tidak larut Tepung tulang Fosfat tidak tersediaBatuan fosfat

PUPUK KALIUM

Bahan dasar pupuk kalium adalah hasil tambang garam kalium (klorida dan sulfat) yang terdapat di Jerman, Perancis dan USA.

BAHAN PUPUK KALIUM

Pupuk Rumus Kimia Persentase Kalium

Kalium klorida KCl 48-60Kalium Sulfat K2SO4 48-50Kalium-magnesium sulfat K dan Mg sulfat 20-30

(25% MgSO4 )Kainit KCl sebagian besar 12-16Kalium Nitrat KNO3 44( 13% N)Abu kayu K2CO3 sebagian besar 3-7 (1-2% P)Abu ampas tebu An-organik 30Abu sabut kelapa An-organik 30Sekam padi Organik 2

PUPUK MIKRO

Garam-garam unsur mikro yg lazim untuk pupuk

Tembaga sulfat CuSO4 25-35% CuTembaga sulfat basa CuSO4. 3Cu(OH)2 13-53% CuTembaga karbonat (basa) CuCO3. Cu(OH)2 57 % CuSeng sulfat ZnSO4 23 - 35% ZnSeng sulfat basa ZnSO4.4 Zn(OH)2 55% ZnMangan sulfat MnSO4 23 % MnMangan sulfat basa MnSO4. MnO 40-49 % MnNatrium Borat Na2B4O7 34-44% B2O3

Fero sulfat FeSO4 20% FeFeri sulfat Fe2(SO4)3 17% FeNatrium molibdat Na2MoO4 37-39% Mo.

PUPUK MAJEMUK

PUPUK CAMPURAN = PUPUK MAJEMUK = pupuk yang mengandung lebihdari satu macam unsur hara esensial N, P, KPUPUK LENGKAP = pupuk yang mengandung unsur hara N, P, K

PENAMPILAN FISIK PUPUK

Umumnya bersifat lepas, sehingga mudah ditabur ke tanahPupuk tidak mudah menggumpal dan mengerasCara menghindarkan penggumpalan:1. Pupuk disimpan dalam kantong kedap air2. Pupuk dicampur dengan bahan yang dapat menyerap air3. Membuat pupuk berbentuk pelet

PENGARUH PUPUK thd pH TANAH

Kebanyakan pupuk majemuk cenderung mengasamkan tanahPengaruh utama adalah karena NH4+ mengalami nitrifikasi:

NH4+ + 2 O2 2H+ + NO3

- + H2O

Yield response curve: The curve below describes the

crop response to fertilizers application

Zone A - Too low fertilizers application which results in

nutrient deficiencies and lower yields

    Zone B - Adequate fertilizers application results in maximum

efficiency and the highest                 profitability.

    Zone C - Over fertilization where yield is not affected but

fertilizers are wasted.    Zone D - Excessive fertilizers

application which results in decreased yields, toxicities and

                 salinity damages

Sumber: www.smart-fertilizer.com/tips-and-info

Careful adjustment of fertilizer application to plant needs and timing for maximum growth benefit.

www.kalkaskacounty.net/planninge...0020.asp

Fertilizer application in this manner is called "banding," as opposed to "broadcasting" over entire field.

Sumber: cals.arizona.edu/extension/susta...sic.html

FERTILIZER PLACEMENT

Potassium fertilizers have been recently used as much as nitrogen and phosphorus

fertilizers and therefore much research work has

been done concerning their placement. Placement of

potassium fertilizer with the seed has appeared to be the

most effective method of application provided the rate of application is not greater than the seed can tolerate.

Sumber:159.226.205.16/curriculum/3w/02/...dex.html

.kapan memupuk padi?........

.. http://ezt.com.my/apply_status/integrated-nutrient-management

Recommended fertilizer application for transplanted Japonica rice with growth duration of 150−155 days. Sumber: www.irri.org/irrc/SSNM/country%2...rice.htm

.MANAJEMEN HARA TANAMAN JAGUNG.

. http://www.soils4teachers.org/fertility.

Site-Specific Nutrient Management (SSNM) for Manual Transplanted Rice in Jiangsu Province, China

Single Japonica rice: 150−155 days growth duration (from seed to harvest)  SSNM is a plant-based approach for ‘feeding’ a rice crop with nutrients as

needed. SSNM includes the following features:

1. Applying sufficient P and K within 14 days after transplanting (DAT) to meet crop needs.

2. Applying only a moderate amount of fertilizer N before active tillering.3. Applying fertilizer N at tillering and later growth stages based on the

needs of the crop for supplemental N as determined with a leaf color chart (LCC).

4. Applying fertilizer K at panicle initiation based on crop needs.5. Using micronutrients based on local recommendations.

The Scientific Basis for Making Fertilizer Recommendations

Yield response as influenced by soil test level and soil test recommendation approach.  (Hergert, 1997)

Konsep Kesuburan TanamanThree main interpretations have developed as a basis for making

fertilizer recommendations. These have developed slowly, but became important during the 1950s and 1960s when soil testing research was

conducted.

Because our research database is limited, general principles are developed so that decisions can be made in areas where all the

desired information is not known. Since agricultural production always includes unknowns, crop fertilization recommendations are based on

interpretation of data and experience.

Reasonable scientists have come to different conclusions on what these general fertility principles are. Some of the differences are due

to geographic location; some are due to the specific nutrient in question; and other differences are due to the value placed on the

many possible objectives.

These three crop nutrition concepts are called: the deficiency correction approach, the maintenance

approach, and nutrient removal. These approaches recognize that:

1)  Only a fraction of a given plant nutrient in the soil is measured by a soil test.

2)  It is impossible to measure how much of a nutrient will be readily available to plants. This means that a soil test

value is an index of the soil’s fertility status, not a quantitative measure of the total amount of nutrient in the

soil or its availability.

3)  Early researchers recognized that the level of available nutrients measured may range from low to high in a given field. Early recommendations were intended to be applied

on a field basis.

Deficiency Correction ApproachThe deficiency correction concept states that a nutrient should be applied only if there is a reasonable expectation of a crop response. The idea of a

limiting factor resulted (Bray, 1944, 1945). This approach is the basis for the correlation and calibration process discussed in Soils - Part 9. A soil test is developed that indicates when a specific nutrient is yield-limiting in a field. Research is conducted to determine crop yields at different soil test levels

for a given nutrient (correlation). The next step determines how much fertilizer is required for optimum yields at different soil test levels

(calibration).This approach requires the most intensive research because the soil test needs to be responsive to changes in soil levels and correlated with crop

response. The two essential questions to be answered are:1)  Will the crop respond to fertilizationþ

2)  How much fertilizer is neededþIn addition, the soil test should be broadly applicable to various crops and across geographic regions. The database should be large enough that a

probability statement can be made with each fertilizer recommendation. For example, “When soil tests for phosphorus are at 10 ppm (Bray and Kurtz

#1), there is a 0-20 percent probability of a yield response to applied phosphorus.” (NebGuide G859, Fertilizer Recommendations for Soybeans)

.Manajemen Hara………...

. http://www.midwestmachinery.co.nz/shop/new/effluent.html.

The advantage of this method is that the only fertilizers applied will be those that increase yields, and these will be

applied at optimum rates.

This has been called “fertilizing the crop,” since emphasis is placed on achieving crop response.

The University of Nebraska soils faculty prefers this method because it is based on UNL research and has been proven over many years. This method is both economical

and environmentally sound.

The deficiency correction approach to fertilizing the crop only recommends fertilizer to the point of economic

optimum yield.

Experience has shown that fertilizer recommendations to correct deficiencies increase the soil test level for most

non-mobile nutrients.

The point called “economic maximum yield” is the yield at which a farmer makes the most profit from fertilizer

If a farmer applies less fertilizer than this, he will save money on his fertilizer bill, but the money lost from

decreased yields will be larger than the money he saved on fertilizer.

If a farmer applies more fertilizer than needed to reach the economic yield, he may increase his yield somewhat, but his fertilizer costs will increase more than the increase in

crop value.

Yield increase x price of corn > lbs of fertilizer x cost of fertilizer

EKONOMI PEMUPUKAN

Use of fertilizers is an index of the use of modern agricultural methods

Faktor lain yg berpengaruh:1. Water control2. Seedbed3. Cultivar4. Date and rate of seeding5. Stand of population6. Fertilizer placement7. Cultivation8. Weed, insect and disease9. Harvesting practices

EKONOMI PUPUK Petani melakukan usahataninya

bertujuan mendapatkan keuntungan yang sebesar-besarnya per satuan luas lahan yang digarapnya ……….. Profit maximizing

The farmer realize that : “he must spend money to make money”

This is certainly true of expenditures for: “lime, fertilizer, and manure”

EKONOMI PUPUK DAN

KAPUR

Level of management on returns from farming

Level of Management:Current Good Superior

Yield, bu per acre 20.0 34.0 50.0Price per unit 2.00 2.00 2.00Value per acre 40.00 68.00 100.00Cost per acre 41.98 53.72 55.75Cost per unit 2.10 1.56 1.11Return over cash -1.98 14.28 44.25

Usahatani kedelai

RETURNS PER RUPIAH SPENT ON FERTILIZER.

Effect of rate of nitrogen on net return per added Rp invested

Nitrogen rate Added input Net return per added Rpkg/ha kg N/ha invested

20 20 7.2540 20 5.7560 20 5.0080 20 3.87100 20 2.38120 20 1.63140 20 0.88160 20 0.50180 20 0.12200 20 -0.62

PROFIT per LAND-AREA.

Petani umumnya akan berupaya melakukan pemupukan untuk mencapai keuntungan (profit) yang setinggi-tingginya per hektar lahannya.

Maximum profit tercapai kalau tambahan hasil sama dengan biaya tambahan terakhir dosis pupuk yang diberikan ( Δ hasil / Δ pupuk).

Aspek ekonomi dari respon hasil jagung terhadap dosis pupuk nitrogen

Dosis N Yield Marginal Marginal Marginal Return Gross profit per ha kg/ha kw/ha Yield Cost ……. (harga jagung Rp 1/ ku) ………..

20 8 8 2.4 3.33 5.6040 15 7 2.4 2.92 10.2060 21 6 2.4 2.50 13.8080 26 5 2.4 2.08 16.40100 30 4 2.4 1.67 18.00120 32 2 2.4 0.83 17.60

Catatan: Harga pupuk N sebesar Rp 0.12 per kg

What are the most profitable rates of plant nutrients?.

Beberapa faktor yang berpengaruh:1. The expected increase in yield from each increment2. The level of management3. The price of fertilizer4. The price the farmer expects to receive for his crops

5. Additional harvesting and marketing costs6. Residual effects7. Levels of other nutrients in the soil or fertilizer

Expected increase in yield from each incement of fertilizer.

Hasil per ha HA

HB Lokasi ALokasi B

HELokasi E

HCLokasi C

HD Lokasi D

N

Dosis pupuk N

Respon tanaman terhadap pemupukan dipengaruhi oleh kesuburan tanah.

Hasil tanaman Tanah kaya P dan K

HK

HM

Tanah miskin P dan K

NDosis pupuk N

Profit PK

Tanah kaya P dan K PM’

profit difference PM

PK’ Tanah Miskin P dan K Max profit

NM NK Dosis pupuk N

Weather effects on the fertilizer response.

Hasil tanaman

HG good weather

HD

dry weather

NDosis pupuk

Price of fertilizer vs. Value of cropHasil tanaman per ha

kurva hasil tanaman Y

C garis biaya pupuk

YC

NC N N’

Dosis pupuk per ha

EKONOMI PEMUPUKAN.

Hasil tanaman yang lebih tinggi akan menyediakan peluang yang lebih besar untuk mencapai maximum net-profit per luasan lahan dan memperkecil biaya produksi per satuan hasil. Kesuburan tanah yang baik menjadi faktor utama untuk mendapatkan hasil yang tinggi. Biaya tetap dalam usahatani adalah biaya yang dikeluarkan oleh petani, tidak tergantung pada besarnya hasil tanaman. Dengan demikian praktek usahatani yang meningkatkan hasil tanaman biasanya akan memperendah biaya produksi per satuan hasil .

Kurva respon hasil tanaman terhadap pemupukan biasanya mengikuti The Law of Diminishing Return (Kurva Asimtotis).Pendapatan per biaya produksi akan semakin menurun, hal ini menjadi pertimbangan utama bagi petani yang modal kerjanya terbatas.

Petani yang progresif biasanya menyadari bahwa profit per hektar lahan lebih penting daripada penghasilan per satuan biaya produksi

Maximum profit dari pemupukan akan tercapai kalau tambahan hasil tanaman sama dengan tambahan biaya pemupukan (dY/dX = dC/dX)

EKONOMI PEMUPUKAN.

Dosis pupuk yang apling menguntungkan dipengatruhi oleh:1. Peningkatan hasil akibat tambahan pupuk2. Level of farm management3. Harga pupuk4. Harga hasil tanaman5. Tambahan biaya panen6. Biaya pemasaran7. Residual effects8. Soil fertility level.

Level of farm management: derajat sampai dimana semua faktor produksi tanaman dapat berhasil dikendalikan.Pada dosis pupuk yang tinggi, diperlukan kemampuan manajerial yg lebih tinggi

Harga per satuan hara tanaman, beragam dengan bahan pupuk.Pupuk yang kandungan haramya lebih tinggi dianggap lebih murah biaya aplikasinya

Prioritas penggunaan modal kerja sangat penting bagi petani.Umumnya lebih menguntungkan untuk melakukan pemupukan sesuai dengan ahsil uji tanah.

EKONOMI PEMUPUKAN

Residual effects pupuk menjadi bagian penting dari ekonomi pemupukan. Semakin banyak jumlah pupuk yang diaplikasikan dalam jangka panjang, maka nilai residual pupuk harus dipertimbangkan.

1. Why high yields are a necessity in periods of low prices ?2. What are fixed cost? Variable costs? In relation to the fertilizer

application3. Discuss the factors that determine the most profitable rate of plant

nutrients.

4. How would you evaluate the residual nutrients in your area?

Maintenance ApproachThe maintenance approach sets a soil test level goal, and

recommends fertilizer to build the soil to the specific nutrient level that has been determined to be ideal. This approach uses soil test levels, as does the deficiency correction approach, to

determine when to fertilize. Soil tests for this approach still have to be correlated, as with the deficiency correction approach. The difference is that emphasis is placed on

maintaining the soil fertility level at or above the point of the economic maximum yield. This has been called “fertilizing the soil,” since emphasis is placed on achieving a specific nutrient

level in the soil. Those who recommend this approach have interpreted the research data to conclude that this approach benefits the producer over time. Generally, the maintenance approach uses a higher soil test level than the critical level

used for the deficiency correction approach.

This approach is used by several midwestern universities. Some soil testing laboratories split

their recommendations into a fertilizer recommendation and a “build” recommendation.

The “build” recommendation is designed to speed the increase in soil test level to the chosen

optimum value.

Whether it applies to soils of a given region must be tested to confirm its validity in terms of crop

response and farm profitability.

A specific example of the maintenance idea is the nutrient balance concept. This concept states that for optimum

crop growth there is a “best ratio” of basic cations (positively charged ions) and a best total base saturation

for a given soil. There has been little information published that confirms that a best cation saturation ratio really

exists for all soils or that it should vary from one soil to another (Leibhardt, 1981; McLean, et. al. 1983).

Because the balance concept includes only calcium, magnesium and potassium, using an extrapolation of the balance concept by applying a ratio approach for making recommendations of micronutrient elements and sulfur is

not valid. This has brought about criticism of laboratories using the

balance concept.

The balance concept resulted from research on soils where cation saturations varied widely.

The initial work (Bear, et al., 1945) was done with alfalfa on one New Jersey soil having uniform

amounts of exchangeable magnesium and hydrogen and variable amounts of exchangeable

potassium and calcium.

From this study, a “best ratio” for the cation composition of the cation exchange capacity

(CEC) was proposed — 65 percent calcium, 10 percent magnesium, 5 percent potassium, and 20

percent hydrogen.

Later work by Graham in Missouri (1959) suggested that the percentages of calcium, magnesium and potassium be

75, 10 and 2.5, but could vary around these values.

The saturation ranges were: 65-85 percent calcium, 6-12 percent magnesium, and 1-5 percent potassium. There is

general agreement that variation of the cation composition in these ranges will not likely affect yield appreciably.

While the idea of keeping a soil in “balance” is appealing, it should not be taken so far as to demand remedial

treatment in most cases. If each nutrient is non-limiting and extreme excess is not apparent, the relative relationship between nutrients will be acceptable

Nutrient Removal Approach

A third approach to fertilizer recommendations still widely used is nutrient removal. Before the advent of soil testing, the nutrient removal approach to

crop fertilization was the best science had to offer. Early agricultural scientists realized that crops obtained their nutrition from the soil and, to maintain good

production, nutrients had to be returned to the soil. This was accomplished through crop residues, wood ashes, and manures. As a simple guideline to

adding fertilizers, the nutrient removal approach is a major advance over not considering crop nutrition at all. The theoretical advantage of returning to the soil what is removed is that productivity is maintained and depletion avoided.

The disadvantage of this approach is that it does not account for the soil’s ability to supply many essential nutrients. Nutrient removal does not recognize that not all nutrients are used at 100 percent efficiency. A producer may under-

or over-fertilize by following the nutrient removal approach. The most profitable fertilization approach needs to consider the cost of farm inputs and environmental concerns. Making fertilizer recommendations by relying on the crop nutrient removal approach ignores these two issues. In addition, a strict adherence to the nutrient removal approach makes soil testing unnecessary,

since nutrients are added based on what is harvested.

48

PRAKTEK TERBAIK PEMUPUKAN - P

PTP-P

Best Management Practices (BMP) For Phosphorus

Fertilization

Reagan M. WaskomExtension Water Quality

SpecialistColorado State University

Cooperative ExtensionAugust 1994

Bulletin #XCM-175

49

Peraturan mengamanatkan kepada semua pihak pengguna bahan agrokimia untuk dapat

mengaplikasikannya secara tepat pestisida dan pupuk

Adopsi PTP-P oleh petani akan membantu mengendalikan pencemaran sumber-sumber air ,

memperbaiki persepsi publik atas industri dan mungkin dapat mengeliminir perlunya regulasi lebih

jauh .

PENDEKATAN PTP-P

. Integrated plant nutrient (IPN) components in the Nepalese farming system.

. http://www.fao.org/docrep/010/ag120e/AG120E10.htm.