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MK. MANAJEMEN KESUBURAN TANAH MANAJEMEN PEMUPUKAN YANG RAMAH-LINGKUNGAN Smno.jurtnh.fpub.2013 MK. MANAJEMEN KESUBURAN TANAH MANAJEMEN PEMUPUKAN YANG RAMAH-LINGKUNGAN.

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Presentasi berjudul: "MK. MANAJEMEN KESUBURAN TANAH MANAJEMEN PEMUPUKAN YANG RAMAH-LINGKUNGAN Smno.jurtnh.fpub.2013 MK. MANAJEMEN KESUBURAN TANAH MANAJEMEN PEMUPUKAN YANG RAMAH-LINGKUNGAN."— Transcript presentasi:

1 MK. MANAJEMEN KESUBURAN TANAH MANAJEMEN PEMUPUKAN YANG RAMAH-LINGKUNGAN Smno.jurtnh.fpub.2013 MK. MANAJEMEN KESUBURAN TANAH MANAJEMEN PEMUPUKAN YANG RAMAH-LINGKUNGAN Smno.jurtnh.fpub.2013

2 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.

3 UNSUR HARA Ada sekitar 14 unsur esensial yg diperoleh tanaman dari tanah Ca dan Mg diberikan ke tanah berbentuk kapur. Unsur hara makro yg paling sering bermasalah adalah N, P, K Ketiga 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 PUPUK 1. Pembawa nitrogen 2. Pembawa fosfat tersedia 3. Pembawa kalium larut air.

4 PEMBAWA NITROGEN Pupuk N juga disebut dengan istilah AMONIAT, ada dua kelompok, yaitu: 1. ORGANIK 2. ANORGANIK PEMBAWA NITROGEN ORGANIK Pupuk 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 keringRumah Potong Hewan Sisa dagingRPH5 -10 (3-13% P2O5) Tepung dagingRPH10-11 (1-5% P2O5) Sisa ikan keringPengolahan ikan (4-8% P2O5) Tepung biji kapasAmpas 6-9 (2-3% P2O5; 1-2% K2O) Batang tembakauSisa (4-9% K2O) Tepung tembakauAmpas (2% P2O5, 1% K2O) Tepung coklatAmpas Sekam padiAmpas1.0 Sumber: Nelson, 1965

5 PEMBAWA NITROGEN ANORGANIK Pertimbangan Umum: Pupuk N anorganik dapat dibuat dari N2 atmosfer dengan teknologi sintetik yang semakin maju. Pupuk Rumus KimiaPersentase Nitrogen Natrium nitratNaNO316 Ammonium sulfat(NH4)2SO421 Amonium nitratNH4NO333 Amonium nitrat gampingNH4NO3 dan dolomit20 UreaCO(NH2) Kalsium sianamidaCaCN222 Amonia cairNH3 cair82 Larutan amoniaNH4OH encer20-25 AmofosNH4H2PO411 (48% P2O5) Diamonium fosfat(NH4)2HPO421(53% P2O5)

6 AMONIA NH3 Gas amonia dibuat dari unsur-unsurnya, Hidrogen dan nitrogen: N2 + 3H NH3 Penggunaannya: 1. Dg menggunakan tekanan tinggi dapat dicairkan menjadi amonia cair 2.Dapat dilarutkan dlm air menjadi NH4OH 3.Gas amonia dipakai untuk pembuatan pupuk lain Bagan pembuatan pupuk Nitrogen: + NH3Am. Nitrat33% N HNO3 Na2CO3Na-nitrat16% N + Batu fosfatNitrofosfat12- 20% N +O2 + H2SO4Am. Sulfat21% N NH3+ H3PO4Am. Fosfat11-21% N + CO2Urea45% N +NH4NO3, +Urea, + H2OLarutan N27-53% N + H2OLarutan amonia20% N

7 PUPUK NITROGEN AMONIUM SULFAT Banyak digunakan oleh petani di Indoensia Dapat digunakan untuk membuat pupuk majemuk Ion NH4+ dalam kondisi aerobik dapat mengalami nitrifikasi Pada sawah NH4+ bereaksi dengan koloid tanah, shg tdk tercuci Pada tanah alkalis memberikan hasil yang memuaskan Natrium & AMONIUM NITRAT Amonium nitrat mengandung ion NH4+ dan NO3- Pemberiannya sebaiknya dlm bentuk pelet, unt mengurangi sifat higroskopis MUDAH MELEDAK BILA TERJADI KEBAKARAN UREA Reaksi pembuatannya: 2NH3 + CO2 NH2COONH4 NH2CONH2 + H2O

8 PUPUK FOSFAT SUPERFOSFAT Kandungan fosfatnya 16-21%, dibuat dengan jalan menambahkan asam sulfat kepada batu fosfat. Ca3(PO4)2 + 2H2SO4 Ca(H2PO4)2 + 2CaSO4 + kotoran CaHPO4 Superfosfat biasa ( 20% P2O5) + H2SO4Pupuk majemuk Batu +H2SO4 or H3PO4 +NH3NH4-fosfat (20-54% P2O5) Fosfat tanur listrik 54% P2O5 TSP (42-50% P2O5) + HNO3 + NH3Nitrofosfat (11-35% P2O5)

9 PUPUK FOSFAT SP : Super Phosphate TSP : Triple Super Phosphate Pupuk Bentuk KimiawiKadar P2O5 tersedia (%)Persen P SuperfosfatCa(H2PO4)2 + CaHPO SuperfosfatNH4H2PO4 amoniatCaHPO4 Ca3(PO4) (3-4%N)7 - 8 (NH4)2SO4 AmofosNH4H2PO448 (11% N)21 Amonium-polifosfat(NH4)4P2O7 & lainnya58-60 (12-15%N)26-27 Diamonium fosfat(NH4)2HPO453 (21% N)23 Sampah tanur baja(CaO)5.P2O5.SiO Batu fosfatFluor atau Klor Apatit Ca-metafosfatCa(PO4) Asam superfosfatH3PO4 dan H4P2O77633

10 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 airCa(H 2 PO 4 ) 2 NH 4 H 2 PO 4 K H 2 PO 4 Fosfat tersedia 2. Larut dlm sitrat: 15% amonium sitrat CaHPO 4 atau 2% asam sitrat 3. Tidak larutTepung tulangFosfat tidak tersedia Batuan fosfat

11 PUPUK KALIUM Bahan dasar pupuk kalium adalah hasil tambang garam kalium (klorida dan sulfat) yang terdapat di Jerman, Perancis dan USA. BAHAN PUPUK KALIUM PupukRumus KimiaPersentase Kalium Kalium kloridaKCl48-60 Kalium SulfatK 2 SO Kalium-magnesium sulfatK dan Mg sulfat20-30 (25% MgSO 4 ) KainitKCl sebagian besar12-16 Kalium NitratKNO 3 44( 13% N) Abu kayuK2CO3 sebagian besar3-7 (1-2% P) Abu ampas tebuAn-organik30 Abu sabut kelapaAn-organik30 Sekam padiOrganik2

12 PUPUK MIKRO Garam-garam unsur mikro yg lazim untuk pupuk Tembaga sulfatCuSO % Cu Tembaga sulfat basaCuSO 4. 3Cu(OH) % Cu Tembaga karbonat (basa)CuCO 3. Cu(OH) 2 57 % Cu Seng sulfatZnSO % Zn Seng sulfat basaZnSO 4.4 Zn(OH) 2 55% Zn Mangan sulfatMnSO 4 23 % Mn Mangan sulfat basaMnSO 4. MnO40-49 % Mn Natrium BoratNa 2 B 4 O % B 2 O 3 Fero sulfatFeSO 4 20% Fe Feri sulfatFe 2 (SO 4 ) 3 17% Fe Natrium molibdatNa 2 MoO % Mo.

13 PUPUK MAJEMUK PUPUK CAMPURAN = PUPUK MAJEMUK = pupuk yang mengandung lebihdari satu macam unsur hara esensial N, P, K PUPUK LENGKAP = pupuk yang mengandung unsur hara N, P, K PENAMPILAN FISIK PUPUK Umumnya bersifat lepas, sehingga mudah ditabur ke tanah Pupuk tidak mudah menggumpal dan mengeras Cara menghindarkan penggumpalan: 1. Pupuk disimpan dalam kantong kedap air 2. Pupuk dicampur dengan bahan yang dapat menyerap air 3. Membuat pupuk berbentuk pelet PENGARUH PUPUK thd pH TANAH Kebanyakan pupuk majemuk cenderung mengasamkan tanah Pengaruh utama adalah karena NH 4 + mengalami nitrifikasi: NH O2 2H + + NO H 2 O

14 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: fertilizer.com/tips-and-info

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

16 Fertilizer application in this manner is called "banding," as opposed to "broadcasting" over entire field. Sumber: cals.arizona.edu/extension/susta...sic.html

17 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: /curriculum /3w/02/...dex.html

18 .kapan memupuk padi?

19 Recommended fertilizer application for transplanted Japonica rice with growth duration of 150−155 days. Sumber:

20 .MANAJEMEN HARA TANAMAN JAGUNG..

21 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.

22 The Scientific Basis for Making Fertilizer Recommendations Yield response as influenced by soil test level and soil test recommendation approach. (Hergert, 1997)

23 Konsep Kesuburan Tanaman Three 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.

24 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.

25 Deficiency Correction Approach The 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 neededþ In 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)(NebGuide G859, Fertilizer Recommendations for Soybeans)

26 .Manajemen Hara………....

27 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.

28 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

29 EKONOMI PEMUPUKAN Use of fertilizers is an index of the use of modern agricultural methods Faktor lain yg berpengaruh: 1.Water control 2.Seedbed 3.Cultivar 4.Date and rate of seeding 5.Stand of population 6.Fertilizer placement 7.Cultivation 8.Weed, insect and disease 9.Harvesting practices Use of fertilizers is an index of the use of modern agricultural methods Faktor lain yg berpengaruh: 1.Water control 2.Seedbed 3.Cultivar 4.Date and rate of seeding 5.Stand of population 6.Fertilizer placement 7.Cultivation 8.Weed, insect and disease 9.Harvesting practices

30 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” The farmer realize that : “he must spend money to make money” This is certainly true of expenditures for: “lime, fertilizer, and manure”

31 EKONOMI PUPUK DAN KAPUR Level of management on returns from farming Level of Management: CurrentGoodSuperior Yield, bu per acre Price per unit Value per acre Cost per acre Cost per unit Return over cash Usahatani kedelai

32 RETURNS PER RUPIAH SPENT ON FERTILIZER. Effect of rate of nitrogen on net return per added Rp invested Nitrogen rateAdded inputNet return per added Rp kg/hakg N/ha invested

33 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 NYieldMarginalMarginalMarginal Return Gross profit per ha kg/ha kw/haYieldCost ……. (harga jagung Rp 1/ ku) ……… Catatan: Harga pupuk N sebesar Rp 0.12 per kg

34 What are the most profitable rates of plant nutrients?. Beberapa faktor yang berpengaruh: 1. The expected increase in yield from each increment 2. The level of management 3. The price of fertilizer 4. The price the farmer expects to receive for his crops 5. Additional harvesting and marketing costs 6. Residual effects 7. Levels of other nutrients in the soil or fertilizer

35 Expected increase in yield from each incement of fertilizer. Hasil per ha HA HBLokasi A Lokasi B HE Lokasi E HC Lokasi C HDLokasi D N Dosis pupuk N

36 Respon tanaman terhadap pemupukan dipengaruhi oleh kesuburan tanah. Hasil tanaman Tanah kaya P dan K H K H M Tanah miskin P dan K N Dosis pupuk N Profit P K Tanah kaya P dan K P M ’ profit difference P M P K ’Tanah Miskin P dan K Max profit N M N K Dosis pupuk N

37 Weather effects on the fertilizer response. Hasil tanaman H G good weather H D dry weather N Dosis pupuk

38 Price of fertilizer vs. Value of crop Hasil tanaman per ha kurva hasil tanaman Y C garis biaya pupuk Y C NC N N’ Dosis pupuk per ha

39 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)

40 EKONOMI PEMUPUKAN. Dosis pupuk yang apling menguntungkan dipengatruhi oleh: 1. Peningkatan hasil akibat tambahan pupuk 2. Level of farm management 3. Harga pupuk 4. Harga hasil tanaman 5. Tambahan biaya panen 6. Biaya pemasaran 7. Residual effects 8. 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.

41 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 application 3.Discuss the factors that determine the most profitable rate of plant nutrients. 4. How would you evaluate the residual nutrients in your area?

42 Maintenance Approach The 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.

43 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.

44 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.

45 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.

46 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: 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

47 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 48 PRAKTEK TERBAIK PEMUPUKAN - P PTP-P Best Management Practices (BMP) For Phosphorus Fertilization Reagan M. Waskom Extension Water Quality Specialist Colorado State University Cooperative Extension August 1994 Bulletin #XCM-175

49 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

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


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