Philippine Journal of Crop Science 2003, 28(1): 39-48 Copyright 2005, Crop Science Society of the Released January 2005

SOIL FERTILITY LIMITATIONS OF RICE TERRACES

TAHERE A SIGARP, NENITAV DESANIER01, JIMMY C CABIGAT2, EMILIO H ABAYAO2 & ALFONSO B CAYONG2 'Philippine Rice Research Institute, Maligaya, Science City of Munoz, Nueva Ecija. 2 Local Government Unit, Ifugao

In 2002 and 2003, a total of 68 soil samples were collected from Ifugao rice terraces in 3 municipalities (, and ) and evaluated for fertility status through 2 methods: (a) minus-one-element test (MOET) and (b) soil analysis (SA). For SA, the samples were dried and sieved while for MOET the samples were kept moist. MOET setups were prepared in 2 replicates planted with PSB Rc44 and Palawan (local variety) following procedures described by Descalsota et al (2001) and Sigari et al (2002). Soils with relative shoot dry weight (RSDW) of 80% or less were considered nutrient-deficient. Likewise, SA was done to measure soil texture, pH, %OM, %0C, total N (%), C:N ratio, available P, exchangeable K, available Zn, S, Cu and soluble Fe. Soils with total N < 0.2%, Olsen P < 6 ppm, exchangeable K < 0.2 cmol/ kg soil, available Zn < 1 ppm, available S < 6 ppm, and available Cu < 0.1 ppm were identified as nutrient-deficient. By MOET, N deficiency was found common to all soils. In Banaue, 31.9% of the soils were recorded as deficient in P, 78.6% in K, 31.9% in Zn, 61.2% in S, and 17.8% in Cu. In Hungduan, 54.7% of the soils were deficient in P, 66.6% in K, 41.9% in Zn, 69.4% in S, and 33.3% in Cu. In Kiangan, 33.6% of the soils were deficient in K, 16.4% in Zn, 38.4% in S, and 28.3% in Cu. The results of SA revealed that all the soils were acidic (pH range 4.8-6.8), mostly with medium texture, and had medium to high levels of OM. In Banaue, soil C:N ratio averaged 16.1, in Hungduan 14.8 and in Kiangan 11.4. In Banaue, 54.1% of the soils were N- deficient, 67.6% P-deficient, 37.8% K-deficient, and 5.4% S-deficient. In Hungduan, 23.8% of the soils were N-deficient, 57.1% P-deficient, 44.4% K-deficient and 4.8% S-deficient. In Kiangan, 100% of the soils were N-deficient and 20% were K-deficient. With data combined, N-, P-, K-, S, and Zn deficiencies appeared to be the major soil fertility limitations of Ifugao rice terraces. Zinc deficiency appeared to be associated with a high amount of OM in the soil, and other limiting factors, making Zn unavailable to the rice plants. Use of organic nutrients with adequate amounts of P and K and improvement of cultural practices to alleviate N-, Zn- and S-deficiencies are recommended. Keywords Ifugao rice terraces, MOET, nutrient deficiency, rice terraces, soil analysis, soil fertility

INTRODUCTION partly because of adverse agro-climatic conditions and partly because of local cultural Geographically, the rice terraces of Ifugao management practices, use of varieties with low- Province, northernLuzon, make up a yielding potential, and poor soil fertility. While magnificentlandscapesculpturedintotheuse of improved rice cultivars with high-yielding mountainsides and have been declared a Worldpotential and tolerancetoadverse climatic HeritageSite(1995).Agriculturally,theirconditions can address the problems of low production is very much below their potential.temperature and low solar radiation, actual Rice yields in such relatively cool, elevated areasyield may not be increased if proper cultural are very low, 2.3 t/ha (CECAP & Philrice 2000), management practices are not adapted and soil fertilityisnot improved appropriately. Past The overall objective of this study was to studies revealed that with appropriate nutrientgenerate data on which to base soil fertility and water management, a rice yield of 5-6 t/harecommendations for Ifugao rice terraces. The could be obtained. In the same studies, it was specific objectives were as follows: shown that rice yield increased with additional a)Evaluateand comparethefertility organic nutrients, but the increases were not status of soils in the rice terraces of proportional to the amount of organic nutrients selected Ifugao towns, those of Banaue, added and in some cases, were not significant at Hungduan and Kiangan. all. Thus, Sigari et al (2002) assumed that either b)Compare and combine the results of two the soil was infertile or the fertility limitation methods of determining soilfertility: was not confined to nitrogen but included other minus-one-element test (MOET) and soil nutrients as well. In both cases,rice yield analysis (SA). increases would be less than that expected as c) Based on theresults, recommend a the green manures were added to the ricefields. fertility management scheme for the rice Thus it appeared necessary to have a detailed terraces to improve yield and increase data on the soil fertility status of rice terraces. income of Ifugao rice farmers. Such data would provide clues in formulating an integrated nutrient management package to MATERIALS & METHODS ensure increased rice yield and higher farmer income. During the years 2002 and 2003, a total of In the province, the farmers recycle almost 68 soil samples were collected from Ifugao rice all the rice straw and weeds into the soil. Toterraces in 3 municipalities,ie, Banaue (39 some extent this helps return nutrients taken up samples), Hungduan (19 samples), and Kiangan by rice plants and weeds. Use of organic matter (10samples).From eachlocation,10soil in the long run, however, may result in the samples were randomly collected down to a 20- accumulation of organic substances especially cm depth and the soil thoroughly mixed. A small under cool climate and continuous flooding. portionof each sample was air-dried and Accumulation of organic substances may in turnpulverized for soil analysis and the rest were aggravate soil acidity, and make some elements kept moist for the MOET. such as Zn and Cu less available to plants A nethouse was installed at the Phil Rice (Dobermann & Fairhurst 2000). CentralExperimentStationinMaligaya, Soil fertility limitations are evaluated byScience City of Mu floz, Nueva Ecija, for the fieldexperiments,planttissueanalysis, MOET setup. Each setup contained 8 plastic observations on the incidences of deficiency orpots (20 cm in diameter and 18 cm in height) per toxicitysymptomsandsoilanalysis.Soil replication, each filled with 4 kg wet soil and analysis has been widely used in diagnosis ofassigned for the following nutrient formulas: soil fertility limitations. complete (soil supplied with the N, P, K, Zn, S, In recent years, a biological technique calledand Cu elements), control, minus N, minus P, theminus-one-elementtest(MOET) was minus K, minus Zn, minus S and minus Cu developed by Phil Rice soil scientists (Descalsota (Descalsota et al 2001). With adequate soil, each et al 1999), with 6 elements under consideration setup was prepared in 2 replications. All the (N, P, K, S, Zn and Cu), whereby experimentalnutrients except N were mixed 3-5 cm into the plants are grown from seed to seed with a soil surface before seeding. The N was added 10 different fertilizer element deliberately missing daysafterseeding (DAS).Initially,5pre- in each treatment; observations on plant growth germinated seeds of rice cultivars PSB Rc44 and arecomparedwithknownsymptomsof Palawan (local variety) were sown into each pot; elemental deficiency. The technique is based onlater, the growing seedlings were thinned to 3 the principle that plant growth is determined orper pot at 10 DAS. The soil was kept submerged limited by the most limiting nutrient in the soil. and water depth increased to 2-3 cm as the The responses are partly manifested by reduced seedlings grew taller. Weekly observations were plantheight,reducedtillercount,delayed made regarding the occurrence of deficiency maturity, smaller panicles and by the presence symptoms and plant growthfactors(plant ofdistinctdiscolorationsuchaschlorosis, height and tiller count). necrosis and/or streaks (Descalsota et al 2000). At 60 DAS, the plants were cut at the base and oven-dried.Soils where total shoot dry 8.3%. C:N ratio averaged 16.1, ranging from 10.3 weight was less than 80% of shoot dry weight ofto 24.1; total N averaged 0.19%, from 0.09% plants grown with complete fertilizer (given all (very low) to 0.38% (medium), Olsen P averaged the 6 elements) were classified as nutrient- 12.7 ppm, from 2.6 ppm (low) to 41.7 ppm (high); deficient (Descalsota et al 2000). exchangeable K averaged 0.25 cmol/ kg soil, Likewise soil samples were analyzed for from 0.1 cmol/ kg soil (low) to 0.97 cmol/ kg soil texture (particle size density), pH (1:1 water: (high); available Zn averaged 5.7 ppm, from 1.1 soil) organic carbon and organic matter content ppm (marginal)to47.7 ppm (veryhigh); (usingthe Walkey-Black method),total Navailable S averaged 20.2 ppm, from 5.2 ppm (Kjeldahl method), available P (Olsen method), (low) to 81.6 ppm (very high), available Cu exchangeable K (ammonium acetate), availableaveraged 13.2 ppm, from 1.9 ppm (medium) to Zn (DTPA), available S (turbidimetric method),21.2 ppm (high); soluble Fe averaged 248 ppm, available Cu (DTPA) and soluble Fe (ammonium from 34.1 ppm (high) to 441.5 ppm (very high). acetate extraction method). Soils with total N

Characteristics Ranges Descriptions Data Source pH 3.0 - 4.0 Extremely acid BSWM, personal 4.0 - 5.0 Acidic communication 5.0 - 6.0 Slightly acidic 6.0 - 7.0 Slightly neutral >7.0 Alkaline C:N >50 presence of high BSWM, personal amounts of biomass communication 15 - 30 well humified 10 optimum BSWM, personal Organic Matter 1 > OM > 8 unfavorable communication Content (%) 1 < OM < 8 favorable Total N (%) N < 0.1 very low BSWM, personal 0.1 < N < 0.2 low communication 0.2 < N < 0.5 medium 0.5 < N < 1 high N > 1 very high Organic Carbon OC < 2 very low BSWM, personal 2 < OC < 4 low (%) communication 4 < OC < 10 medium 10 < OC < 20 high OC > 20 very high Available P P < 6 low Dobermann and (ppm) 6 < P < 10 medium Fairhust (2000) P > 10 high Exchangeable K K < 0. 2 low (cmol/ kg soil) BSWM, personal 0.2 < K < 0.4 medium communication 0.4 < K < 0.8 high K > 0.8 very high

Available S S < 6 low Dobermann and (ppm) 6 < S < 9 medium Fairhust (2000) S > 9 high Available Zn Zn < 0.5 very low BSWM, personal (ppm) 0.5 < Zn < 1 low communication 1 < Zn < 5 medium 5 < Zn < 20 high Zn > 20 very high Cu (ppm) Cu < 0.1 low BSWM, personal Cu > 0.1 adequate communication Soluble Fe Fe < 1 very low BSWM, personal (ppm) 1 < Fe < 6 low communication 6 < Fe < 14 medium 14 < Fe < 31 high Fe > 31 very high

42 Tahere A Sigari et al In Kiangan, soil pH averaged 5.9, rangingin Hungduan, 20% in Kiangan contained high from 4.8 (acidic) to 6.8 (slightly neutral); OM levels of exchangeable K (Figure 6). Without content averaged 4.3%, from 2.8% to 5.1%; C:N exception, available Zn levels in all soils were ratio averaged 11.4, from 9.3 to 13.9; total Nhigher than 1 ppm. Only 10.8% of the soils in averaged 0.14%, from 0.12% (low) to 0.18% (low); Banaue, 4.8% in Hungduan and 10% in Kiangan available P averaged 13.6 ppm, from 18.1 ppmcontained marginal levels(1.0-1.5 ppm) of (high)to35.1 ppm (high);exchangeable Kavailable Zn (Figure 7). Of available S, 5.4% of averaged 0.42 cmol/ kg soil, from 0.1 cmol/ kg the soils in Banaue, 19% in Hungduan, and 10% in Kiangan showed medium 120 - levels (6

0 Fri Fe3+toFe2+,increasein N P K Zn s Cu available N, P, K, Si, and Mo, Nutrient element decrease in availability of S, Fig 2. Frequency distribution of soils from Ifugao rice terraces for Zn, and Cu and generation of nutrient deficiencies (SA) organic toxics. Probability of Zn and Cu deficiencies soil (low) to 0.8 cmol/ kg (high); available Znbecomes highin organic soils that are poorly averaged 3.6 ppm, from 1.5 ppm (marginal) to drained. 4.8 ppm (high); available S averaged 11.4 ppm, Within4-6weeksafterflooding,the from 8.9 ppm (medium) to 12.7 ppm (high); concentration of water soluble SO4 2in most soils available Cu averaged 20.3 ppm, from 9.0 ppmdrops to almost zero (Ponnamperuma 1985). (medium) to30.2 ppm(high);soluble FePlants require S in the form of S0421 from the averaged 209 ppm, 155.3 ppm (very high) to soil solution. Reduction of S0421 to elemental S , 340.7 ppm (very high). As to texture, 20% of theandtheformationofsulfidesfollowthe soils were loam, 20% silt loam, 20% clay loam, and 40% were clay (Table 4). 50 In pH, 18.9% of the soils in Banaue, 23.8% in 45 Banue ClHungduan Kiangan Hungduan and 20% in Kiangan had pH less than 5. Soil pH of the rest was higher than 5 and 40 less than 7. The soils of Kiangan were relatively 35 30 less acidic (Figure 3). Of OM, 10.8% of the soil in c Banaue and 14.3% in Hungduan contained more 25 cr than 8%. Soils of Kiangan appeared to have less 220 LL OM than thoseof Banaue and Hungduan 15 (Figure 4). Of available P, 43.2% of the soils in 10 Banaue and 38.1% in Hungduan contained 5 medium to high levels. In Kiangan, all the soils 0 4.5-5 5-5.5 5.5-6 6-6.5 >6.5 contained sufficient level of P (Figure 5). Most pH thesoilscontained relatively low levelsof Fig3. Frequency distribution of soils from exchangeable K, ie, only 5.4% in Banaue, 9.6% Ifugao rice terraces for pH reduction of Fe3+ to Fe2+ in a flooded soil. Sstraw and chicken manure, increases microbial availability decreases as soil reduction proceeds. activities for N mineralization; however, if the As the result, S can become deficient; Fe, Zn and manuresareusedalone, N may become Cu become immobilized and H2S toxicity cantemporarily less available. On the other hand occur in soils containing small amounts of Fe use of green manure alone may not be the proper (Dobermann & Fairhurst2000).Increased means to alleviate P and K deficiencies but to concentration of soluble Fe in submerged soils provide more N available to rice plants. containing high amounts of organic matter The findings indicated that the soil fertility contributes largely to decreased availability of P, varied within and between the locations. In most S, Cu and Zn. The availability of Cu decreases at cases, the variations within each municipality flooding because of the formation of insoluble Cu were higher than those observed between the sulfides and Cu ferrites and complexes withmunicipalities. In general, however, the soils of organic matter. The plant availability of CuKiangan contained less amounts of OM but decreaseswithincreasing pH and organicappeared rich in P and had more balanced matter content. Likewise, Zn uptake is reduced fertility components. The paddy soil-rice system by an increase in the concentration of organichas an efficient nutrient replenishing acids that occurs under submerged conditionsmechanism. In some Asia paddy fields, rice has (Dobermann & Fairhurst 2000). Comparisonoforganiccarbonand NTable 2. Chemical properties and texture indicates that most of the organic matter are of soil from Banquet rice terraces well humified and have become stabilized in the (Ifugao 2002-2003) soil. The extent of humification was higher in Kiangan than Hungduan and Banaue. Likewise, Chemical Average Range soils of Kiangan contained less OM and total N, Properties pH 5.1 4.8-6.5 80 Banue Hungduan Kiangan OM (%) 4.9 1.9-8.3 70 C:N 16.1 10.3-24.1 60 Total N (%) 0.19 0.09-0.38 >, 50 c(..) g 40 Olsen P (ppm) 12.7 2.6-41.7 D- LLE 30 Exch. K (cmol/ kg) 0.25 0.1-0.97

20 Available Zn (ppm) 5.7 1.1-47.7 10 Available S (ppm) 20.2 5.2-81.6 0 0-2 2-4 4-6 6-8 8-10 1012 Available Cu (ppm) 13.2 1.9-21.2 OM% Fig 4. Frequency distribution of Ifugao rice Soluble Fe (ppm) 248 34.1-414.5 terraces soils for organic matter content but appeared with more balanced amounts of P,been cultivated for hundreds of years without S, Zn and Cu. MOET results also indicatedreceiving any fertilizer and yet yields of 1.6 to 2 comparatively lower Zn and S deficiencies in t/ha have been sustained (Kyuma 1996). Kiangan. The farmers in the province recycle rice SUMMARY straws and weeds into thesoil.Rice straw contains 0.8% N, 3.7% K and 1.2% P; therefore, 1 Table5summarizes and compares the ton straw provides 8 kg N, 37 kg K and 12 kg P, values obtained through the MOET and SA in and increases soil organic matter (De Dattaterms of soil deficiencies in N, P, K, Zn, S and 1981). Green manures with a narrow C: N ratioCu in the 3 study sites: Banaue, Hungduan, and are rich in N but have littlepotential for Kiangan, all in Ifugao Province. increasing soil organic matter overtime. Use of By method of analysisforsoilfertility organic fertilizers high in C:N ratio, such as deficiency, MOET showed that all the samplewere acidic, contained relatively high level and well-humified organic matter, and were deficient in N, P, and K. The results of MOET confirmed Table 3. Chemical properties and the SA findings and indicated that the soils were texture of soil from Hungduan also deficient in S and Zn. The soil fertility levels rice terraces (Ifugao 2001 2003) varied within and between the 3 municipalities; however,ingeneralthesoilsof Kiangan Chemical Average Range contained less amounts of organic matter, but Properties had adequate levels of available P and appeared pH 5.3 4.7-6 with more balanced nutrient components, and consequently with no incidences of Zn and S OM (%) 6 3.2-12 deficiencies. C:N 14.8 11-18.3 Since soil analysis is the prevalent method of determining nutrient deficiency of soils, and the Total N (%) 0.28 0.14-0.42 SA results differed much from those of MOET, Olsen P (ppm) 12.4 1.5-29.6 which is a promising method, it is recommended that further studies be conducted comparing the Exch. K (cmol/ kg) 0.23 0.08-0.98 results of the two methods in studies involving Available Zn 2.97 1.2-5.5 the determination of soil deficiency levels and (ppm) actual application of the findings in farmers' fields. Available S (ppm) 12.7 5.1-39.2 The current farmer's practice of recycling Available Cu 11.6 6.7-20.2 rice straw and weeds may be able to satisfy the (ppm) objective of rice yields of 2-3 t/ha, but if higher yields are desired, then more balanced and Soluble Fe (ppm) 333.1 146.3-440.6 higher quantities of organic fertilizers have to be developed and applied. Organic resources high not only in N, P, and K but also in Zn, S and Cu soils were highly deficient in N, P, K, Zn, S and must be explored and used. In addition to rice potentially in Cu, while SA showed only majorstraw, adequate amounts of organic fertilizers N-, P-, K-deficiencies and potential S-deficiency. must be supplied to reach the target yields of 5-6 Thelevelsofdeficiencieswerealsoveryt/ha. different, with MOET values mostly higher than Improvement of cultural management such SA values. as by adopting the use of high-quality seeds, use By element, not only the traditional majorof high-yielding varieties, use of healthy and elements - N, P, K - were found to be highlyvigorous seedlings, proper water and pest and deficient in the soils, but also Zn and S. It is noteworthy that MOET shows all sample soils 100 - from the 3 study sites highly deficient in N. Banue Hungduan Kiangan By study site, on one hand, the deficiencies 90 - in Hungduan were generally higher than those 80 - in Banaue and more so than in Kiangan, 70 -

according to MOET results. On the other hand, e>,60 - the opposite is true according to SA results. cU ca) 50 - From the results of both MOET and SA, it is cr a) 40 - seen that N, P and K deficiencies are the major Li soil problems of rice terraces. By MOET alone, it 30 - is seen that the soils are deficient in elements S and Zn and potentially deficient in Cu. 20 - 10 - CONCLUSIONS & RECOMMENDATIONS 0 E 0 -5 5 -10 10 -15 15-20 >20 P,ppm The results of soil analysis revealed that Fig 5. Frequency distribution of soils from most of the soil samples from the rice terraces Ifugao rice terraces for available p diseasemanagement,shouldbeeffective by using these resources. However, the use of measures to make the soils in the rice terracesgreen manures maynotbe appropriate in soils more fertile and the rice plants more productive.with low available P and K, so that other Occasional drainage should make P, Zn, Cu, S,resources high in P and K must be explored and and P more available to rice plants. used. To help protect the rice terraces as a World Occasional drainage of the terraces not only HeritageSiteandtoavoid any ecologicalwould facilitatesoil aeration and accelerate disturbances, the use of inorganic fertilizers is decompositionoforganicmatter,butalso notrecommended. Abundant natural sources ofminimize the risk of the accumulation of toxic organic fertilizersstill give the province thesubstances. opportunity to sustain and elevate soil fertility

References Azhiri-Sigari T, JC Cabigat, AB Cayong, EH Abayao & NV Desamero. 2003. Nutrient and water management for increased rice yield in cool elevated area. Annual Report for 2002, Phil Rice, Maligaya, Mu lioz, Nueva Ecija Azhiri-Sigari T, JC Cabigat, RF Orge, EU Bautista, CJM Tado, NB Hamor, AB Mataia & CB Casiwan. 2002. Nutrient and water management for increased rice yield in cool elevated area. Annual Report for 2001, Phil Rice, Maligaya, Mu lioz, Nueva Ecija CECAP & Phil Rice. 2000. Highland Rice Production in the Philippine Cordillera. Central Cordillera Agricultural Program (CECAP), Banaue, Ifugao and Philippine Rice Research Institute (Phil Rice), Maligaya, Mu lioz, Nueva Ecija De Datta SK. 1981. Principles And Practices Of Rice Production. John Wiley & Sons, Inc, Singapore Descalsota JP, CP Mamaril & GO San Valentin. 1999. Evaluation of the soil fertility status of some rice soils in the Philippines. Paper presented at the 2nd annual meeting and symposium of the Philippines Society of Soil Science and Technology Inc, State University, La Trinidad, Benguet, May 20-21 Table 4. Chemical properties and texture of soil from Kiangan rice terraces (Ifugao 2002 2003)

Chemical Average Range 40 Properties Banue Hungduan Kiangan 35 pH 5.9 4.8-6.8 30 OM (%) 4.3 2.8-5.1 C:N 11.4 9.3-13.9 25 Total N (%) 0.14 0.12-0.18 20 I Olsen P (ppm) 13.6 18.1-35.1 15 Exch. K (cmol/ kg) 0.42 0.1-0.8 10 1- Available Zn 3.6 1.5-4.8 (ppm) 0-0.1 0.1-0.2 0.2-0.3 0.3-0.4 0.4-0.5 >0.5 Available S (ppm) 11.4 8.9-12.7 Exchangeble K ( cmol/kg soil) Available Cu 20.3 9-30.2 Fig 6. Frequency distribution of soils from Ifugao rice terraces for exchangable K (ppm) Soluble Fe (ppm) 209 155.3- 340.7 Descalsota JP, CP Mamaril, GO San Valentin, AL Ayo, TM Corton & SR Obien. 2001. Minus-One Element Technique of diagnosis nutrient limitation and balancing fertilizer application in lowland rice soils. Paper presented in 14th National Rice Research and development Conference, Phil Rice, Maligaya, Mu lioz, Nueva Ecija, March 7-9 Doberman A & T Fairhurst. 2000. Rice: Nutrient Disorders and Nutrient Management. Potash and Phosphate institute (PPI), Potash and Phosphate Institute of Canada (PPIC) and International Rice Research Institute (IRRI) Kyuma K. 1996. Ecological Sustainability of Paddy Soil-Rice System in Asia: Inappropriate use of Fertilizers in Asia and the Pacific. A Saleem (ed), Proceedings Of The APO-FFTC Seminar On Appropriate Use Of Fertilizers, held in Taiwan, November 6-14, 1995, pp 128-142 PCARR. 1980, Standard methods of analysis for soil, plant tissue, water and fertilizer. Philippine Council for Agriculture and Resources Research (PCARR), Los Balios, Laguna Ponnamperuma FN. 1984. Effect of flooding on soils. In Flooding And Plant Growth. TT Koslowski (ed). Academic Press, New York Ponnamperuma FN. 1994, Evaluation and improvement of lands for wetland rice production, In Rice And Problem Soils In South And Southeast Asia, D Senadhira (ed), IRRI Discussion Paper Series. International Rice Research Institute, PO Box 933, Manila, Philippines

90 60 80 - Banue Hungduan Kiang an Banue Hungduan Kiang an 50 - 70 -

e 60 - 40 2 50 - .40a) - 3 30 - 3- a) 6:30 - 20 - 20 - 10 - 10 -

0 0 <1.5 1 5 5 5 -10 10-15 3 -6 6 -9 9 -12 12-15 >15 Available Zn, ppm S (ppm) Fig 7. Frequency distribution of soils from Fig 8. Frequency distribution of soils from Ifugao rice terraces for available Zinc Ifugao rice terraces for available S 100 Banue Hungduan Kiangan 90 80

70 60 a 50 a- 40 EL2 u_ 30 20

10

0 1-6 6-14 14-31 Available Cu, ppm Fig 9. Frequency distribution of soils from Ifugao rice terraces for available Cu Table 5. Results of nutrie deficiency analysis by MOET and SA of soils in the rice terraces of 3 selected municipalities of Ifugao Test/Study Site Percent Of Sample Soils Deficient In In Ifugao Province N P K Zn S Cu Minus-One-Element Test (MOET) Banaue 100 31.9 78.6 31.9 61.2 17.8 Hungduan 100 54.7 66.6 41.9 69.4 33.3 Kiangan 100 ND 33.6 16.4 38.4 28.3 Soil Analysis (SA) Banaue 54.1 67.6 37.8 ND 5.4 ND Hungduan 23.8 57.1 44.4 ND 4.8 ND Kiangan 100 ND 20 ND ND ND ND = no deficiency

48 Tahere A Sigari et al