COELHO, A. M.

CUNHA, T. F.

LIMA, G. J. de O.

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18th Sydiposium ofthe Internationai Scientific Centre ofFertilizers, Rome (Italy), 8·12 November 2009 85SITE SPECIFIC SOIL FERTILITY MANAGEMENT OF AN OXISOL CULTIV ATEDWITH CORN FOR APPLICATION OF LIME AND GYPSUM ,..A.M. Coelho', G.J. de O. Lima", T.F. Cunha''Embrapa Maize and Sorghum Research Institute, Sete Lagoas- MG, Brazil,E-mail: al1}coelho@cnpms.embrapa.br, telephone +55-31-3027-1145, fax +55-31- 3027-1188"Campo Agricultural and Environmental Analyses, Paracatu-MG, Brazil,E-mail: ap@campoanalises.com.br, telephone +55-38-3671-1164IV Session: Fertilization and environrnental qualityAbstractDue to the necessity to improve soil fertility diagnostic, the researches have been searched for'''1ore efficient technologies on agronornic and environrnental aspects. One of these technologies is1euse of the concept of site specific for soil fertility management. This research was conducted ina farm field (100 ha) located in Corinto, Minas Gerais state, in the 200712008 growing season. Thesoil is classified as Silt Clay Oxisol, cropped with com and irrigated with a center-pivot sprinklerirrigation system. Grid cell of 1 ha, was used for collecting soil samples from O to 20 em asd 20 to40 em depths. Data ofpH, Ae+, Ca2+, Mg2+, CEC, base saturation (BS), A13+saturation and organicmatter were submitted to geostatistical analysis and interpolated by point-kriging using the modeledsemi-variograms. Based on the maps of BS and Ae+ saturation, it was possible to define zones ofmanagement for application of lime and gypsum. The threshold used to the definition of the rates oflime was 60 % of BS in the top of 20 cm. The criteria based on values of Ca «0.5 cmok/dm") andA13+ saturation (>25 %) in the subsoil (20 to 40 em) were used for gypsum application. With theseinformations, maps of application of lime and gypsum at variable rate were generated. The rates oflime range from O to 3 t/ha and for gypsum of O and 1 t/ha. The costs of soil sampling with GPS,soil chemical analyses, field mapping with GIS and application oflime and gypsum, are evaluated.Book of Abstracts - ClEC 2009

Site specific soil fertility management of an oxisol cultivated with corn for application of lime and gypsum.

More Sustainability in AgricuIture: New Fertilizers and Fertilization Management _18th Intemational Symposium ofCIECSITE SPECIFIC SOIL FERTILITY MANAGEMENT OF AN OXISOLCULTIVATED WITH CORN FOR APPLICATION OF LIME AND GYPSUMA. M. Coelhot, G. J. de O. Lima', T. F. Cunha2'Embrapa Maize and Sorghum Research Institute, Sete Lagoas- MG, Brazil,e-mail: amcoelho@cnprns.embrapa.br, phone +5:::-31-3027-1145, fax +55-31- 3027-11882Campo Agricultural and Environrnental Analyses, Paracatu-MG, Brazil,e-mail: ap(a).campoanalises.com.br. phone +55-38-3671-1164AbstractDue to the necessity to improve soil fertility diagnostic, the researchers have been searched formore efficient technologies on agronomic, economic and environrnental aspects. One of thesetechnologies is the use of the concept of site-specific for soil fertility management. Thisresearch was conducted in a farm field (100 ha) located in Corinto, Minas Gerais state, startingin the 2007-2008 growing season. The soil is classified as Clay Oxisol, cropped with com (Zeamays L.) and irrigated with a center-pivot sprinkler irrigation system. Grid cell of 1 ha wasused for colIecting soil samples from O to 20 em and 20 to 40 em depths. Data of pH, AI3+,Ca2+, Mg2+, CEC, base saturation (BS), A13+ saturation in the CEC at soil pH (effective CEC)and organic matter were submitted to geostatistical analysis and interpolated by point-krigingusing the modeled semi-variograms. Based on the maps of BS and Ae+ saturation, it waspossible to define zones of management for application of lime and gypsum. The thresholdused to the definition of the rates of lime was 60 % of BS in the top of 20 em. The criteriabased on values of Ca «0.5 cmol, dm') and Ae+ saturation (>25 %) in the subsoil (20 to 40em) were used for gypsum application. With these informations, maps of application of limeand gypsum at variable rate were generated. The rates of lime range from O to 3 t ha" and forgypsum of O and 1 t ha-1• The costs of soil sampling with GPS, soil chemical analyses, fieldmapping with GIS and application of lime and gypsum, were evaluated. Allocating the cost ofsite-specific soil acidity management, over a useful lifetime of four years, the cost of thetechnological package, US$ 18.40 per hectare, become economicalIy feasible.Keywords: soil acidity, spatial variability, variable rate, economic aspects, Zea mays L.IntroductionSoil analysis should be the basis for alI programs of soil fertility evaluation and the building ofa nutrient management plano It can be complemented by other techniques, but it is the only one262 Proceedings - CIEC 2009More Sustainability in Agriculture: New Fertilizers andFertilization Management _18th IntemationalSymposiumofCIECthat efficiently, on a routine basis, makes it possible to anticipate the existing soil constraint forthe growth and development of plants. In general, the current soil tests performed in thelaboratories in Brazil, are both precise and accurate in determining the nutrient supplyingpower of the soil that is being analyzed. Most states also have certification programs thatensure that the laboratories are performing the correct test and are proficient in the exactprocedure (Cantarella, 1999). However, the greatest difficulty for soil fertility evaluation iscollecting the right soil samples to test and that represents the area sampled. Also, soilsampling has often been described as the weak link in soil testing. Thus, there is the necessityto improve soil fertility diagnostic, and the researchers have been searched for more efficienttechnologies on agronomic, economic and environmental aspects.One of these technologies is the use of the concept of site-specific for soil fertilitymanagement. It is based on information about spatial variability of soil attributes and involvecustomize management of fertilizer and soil amendments (lime and gypsum), in sub-regions ofa field, in order to reduce soil variability, optimizing productivity and profitability (Mulla andHemández, 2006; Coelho, 2008a). The aim of precision farming research is to help farmersoptimize the management of their fie1ds so that gross returns are maximized for eachmanagement area. To do this, the farmer needs to know how the conditions for growing cropsvary over the area of interest. The objective of this research was to identify the spatialvariability of soil fertility, with emphasis in the soil acidity, to define management zones forapplication of lime and gypsum at variable rate, in an Oxisol cropped with com. Also,theprofitability was evaluated to obtain the balance cost of soil sampling with the value 'ofinformation.Materiais and MethodsThis research was conducted in a farm field (100 ha) located in Corinto (18° 13'S, 44° 36'W,550 m above sea level), Minas Gerais state, starting in the 2007-2008 growing season. The soilis classified as Clay Oxisol (47 % of clay), cropped with com and irrigated with a center-pivotsprinkler irrigation system. A georeferenced grid cell of 1 ha, was used for collecting soilsamples from O to 20 em and 20 to 40 em depths. Five soil cores were randomly collectedwithin a 5-m radius ofthe grid-line intersection (node) and composited as one soil sample. Soiltest analyses were carried out according to methodology described by Embrapa (1997). Data ofpH, A13+,Ca2+, Mg2+, CEC, percent base saturation (BS), percent A13+saturation in the CEC atsoil pH (effective CEC) and organic matter were submitted to geostatistical analysis, asdescribed by Isaaks and Srivastava (1989), and interpolated by point-kriging using the modeledsemi-variograms, Based on the maps of BS and Ae+ saturation, it was possible to defme zonesProceedings - CIEC 2009 263More Sustainability in Agriculture: New Fertilizers and Fertilization Management - 18th IntemationalSymposiumofCIECof management for application of lime and gypsum. The threshold used to the definition of therates of lime was 60 % of BS in the top of 20 em. The eriteria based on values of Ca «0.5cmol, dm") and A13+ saturation (>25 %) in the subsoil (20 to 40 em) were used for gypsumapplieation. The ealculation of the rates of lime to bring soil BS to 60 %, was based on thefollowing equation: RLIOO = [(60 - BS)*CEC/I00]. Where, RLIOO is the rate oflime with theeffective ealcium earbonate rating of 100 %. The rates of gypsum were based on clay content,according to Alvarez V, et al (1999). With these informations, maps of applieation of lime andgypsum at variable rate were generated. Based on these maps, lime and gypsum were appliedat variable rates, on the soil surface, using a eommereial spreader applicator. The costs of soilsampling with GPS, soil chemical analyses, field mapping with GIS and application of limeand gypsum at variable rate, are evaluated.Results and DiscussionSince this study is ongoing, a complete analysis of site-specific soil fertility management is notyet possible. However, the observed spatial variability in the com crop yield and nutrient levelshas important implications for both variable and constant rate fertilizer and soil amendment(lime and gypsum) applications. The site in this study show large spatial variability in the soilattributes used as indicators of the soil acidity (Figure lac). In the topsoil (20 em), spatialpattems in kriged BS (Figure Ia) show values ranging from about 40-60 % in a 100-ha field.The BS is approaching the deficiency in part southwest of the field « 50 %), yet is plentiful(BS > 50 %) in parts northwest and southeast of the field. This variability (Figure Ia) affordthe opportunity to differential application of limestone and the modem technology of precisionfarming. The spatial scale makes it feasible technologically. According to National ResearchCouncil (1997), soil variation is of interest when conditions vary over patches manageable byagricultural machinery.Based on map of BS (Figure Ia), four management zones were established for limestoneapplication (Figure 1b): zone 1 - 0.0 t ha", representing 27 ha; zone 2 - 0.3 to <1.0 t ha-t,representing 21 ha; zone 3 - 1.0 to <2.0 t ha-1, representing 38 ha and; zone 4 - 2.0 to 3.0 t ha",representing 13 ha. Field-averaged soil test for BS was 49 ± 10 %. For com crop, the values ofBS of 50 to 60 % are recommended (Coelho, 2008b). If the field is to be uniformly liming at asingle rate to bring BS to 60 %, according to recommendation for com, there is a necessity of1.0 t ha-1 of limestone. Although the total comsuption of the limestone (99 t), is similar forboth, uniform and variable rate application, the large variability in the soil acidity, justify theuse ofvariable rate technology.264 Proceedings - CIEC 2009More Sustainability in Agriculture: New Fertilizers and Fertilization Management - 18th lnternationalSymposiumofCIEC+BS -O-2Ocm (%)E2J 40,23,44,0344,03·47,41• 47,41,50,80.50,80-54,02.54,02-61,3ê-..•..•.. -a) Map ofbase saturation 0-20 em depth+ACSat 2040cm C%)~ 1.,05-28,90_ 28,.'-34,75_34,7.-42,80_ ",., -50,44_ 50,45-58,30c) Map of Ae+ saturation 20-40 em depth+Ume(tIha)~0,OO-O,5O.0,51-1,21.,,22-,,80.,,8,-3,00b) Map of lime application+Gypsum(tlha)~O,OO-O,19B°.20-0,52.0,53-0,83.0,84-1,00d) Map of gypsum applicationFigure 1: Interpolated maps of base saturation (a); lime application (b); aluminum saturation(c) and, gypsum application (d).For Ae+ saturation in the CEC at soil pH, the values in the soil surface range from O to 35 %(data not showed). The subsoil (20 - 40 em) presented high acidity, with values of A13+saturation ranging from 20 to 58 % in almost alI fie1d (Figure lc). Thus, according to criteriafor gypsum recommendation, in 70 ha of the field, there is the opportunity for gypsumapplication at maximum rate of the 1.0 t ha" (Figure ld). Research reported by Prado (2001)showed for some com hybrids, that grain yie1d was reduced by 47 % in an oxisol with A13+saturation of 23 % in the topsoil (0-20 em). The results presented and discussed here, show thatthe conventional approache to soil testing, based on average, was inadequate for characterizingspatial variation of soil acidity. However, only the economic conspire against it, because oftheneed to analysis the soil for nutrients at least 99 points at two depths, and the cost of that in anyone year could be more than the farmer can expect to gain in greater efficiency. In the Table I,are showing the annual costs for application of lime and gypsum at variable rate for a 100-hectare field.Proceedings- CIEC 2009 265More Sustainability in Agriculture: New Fertilizers and Fertilization Management _181h IntemationalSymposiumofCIECTable I: Annual information costs for application of lime and gypsum at variable rate f,or a100hectare field, with a 4-year soil sampling cycle.Activities Price (US$/ha) Amount (US$)Soil sampling labor 0-20 em depth(lha grid) 5.00 500.00Soil sampling labor 20-40 em depth (lha grid) 5.00 500.00Soil test lab analyses (l98 samplesj'' 10.00 1,980.00Constructing soil test results maps with GIS 4.00 400.00Lime application (72 ha) 18.00 1,296.00Gypsum application (70 ha) 18.00 1,260.008.428.4233.356.7421.8321.23Total variable cost 5,936.00 100.00Cost of capital (discount rate 6 % a.a.) 356.16Depreciation (4 years) 1,484.00Annualized cost for 100-hectare field 1,840.16Annualized cost per hectare 18.40liAssumes a composite sample for each hectare. Cosi of soil test lab analyses US$1 0,00 per sample for analyses ofpH, Al, H+Al, Ca, Mg, P, K and organic matter.'FJi~;iotalvariable cost (Table 1), for grid soil sampling, laboratory analyses, building soil maps~:;t''r..~.= .anel;'application of lime and gypsum for 100ha field was US$ 5,936.00, which represent a cost,ofthe US$ 59.36 ha". However, according to National Research Council (1997), theinformation gained from sampling and mapping soil phosphorus, potassium and, soil acidity, isoften used for three to five years, allowing sampling and analysis cost to be amortized overseveral growing seasons. Thus, allocating the C,ostof soil acidity management over a usefullifetime of four years, the cost of this technological package become relatively reasonable, US$18.40 ha" (Table 1). It is important to remember that this cost was obtained for an intensivegrid soil sampling of 1 ha and, collecting samples from two depths. According to Hennessy etaI. (1996), optimal sampling depends on trade-offs between potential savings in inputexpenditures, potential gains from increased yields due t,o improved management, andsampling costs.ConclusionsThe conventional approache to soil testing, based ,on averages, was inadequate forcharacterizing spatial variation of soil acidity. Intensive grid sampling conducted for precisionfarming studies showed that the indicators of the soil acidity levels within field are variable andcan be mapped into management units suitable for variable rate application technology, Theannualized cost (US$ 18.40 per hectare) of intensive grid sampling was economically feasible.Since this study is ongoing, little information is available t,odescribe the long-term effects ,onsoil productivity. Innovative soil fertility manager should consider field heterogeneity as a266 Proceedings - CIEC 2009More Sustainability in Agriculture: New Fertilizers and Fertilization Management _18th IntemationalSymposiumofCIECpotential altemative to conventional strategies and a way to improve fertilizer profitability,particular1yif appropriate yield goals and fertilizer recommendation can be developed.ReferencesAlvarez V.V.H.; Dias, L.E.; Ribeiro, C.A. e Souza, R.B.de., 1999: Uso de gesso agrícola.In: Recomendação para o uso de corretivos e fertilizantes em Minas Gerais. Comissão deFertilidade do Solo do Estado de Minas Gerais. (eds A.C. Ribeiro, P.T.G. Guimarães and V.H.Alvarez V). Viçosa. p. 67-78.Cantarella, H., 1999: A qualidade da análise de solo. ln: lnter-relação fertilidade, biologia dosolo e nutrição de plantas (eds J. o. Siqueira, F. M. S. Moreira, A. S. Lopes, L. R G.Guilherme, V. Faquin, A. E. Furtini Neto and J. G. Carvalho). Lavras:SBCSIUFLAlDepartamento de Ciência do Solo. p. 321-335.Coelho, A.M., 2008a: Agricultura de precisão em sistemas agrícolas. In: Savanas: dasafios eestratégias para o equíliibrio entre a sociedade, agronegócio e recursos naturais. (eds F.G.Faleiro, and A.L. de Farias Neto). Planaltina: Embrapa Cerrados, p. 1063-1080.Coelho, A.M., 2008b: Nutrição e adubação do milho. ln: A cultura do milho. (eds J.C Cruz, D.Karam, M.A. R. Monteiro and P.C. Magalhães). Sete Lagoas: Embrapa Milho e Sorgo. capo6,p.131-157.Empresa Brasileira de Pesquisa Agropecuária-Embrapa, 1997: Centro Nacional dePesquisa de Solos. Manual de métodos de análise de solo. 2.ed. Rio de Janeiro. 212p.Hennessy, D.A., Babcock, B.A. and Fiez, T.E., 1996: Effects of site-specific management onthe application of agricultural imputs. Pullman, Wash.: Department of Agriculture Economics,Washington State University.Isaaks, E.H. and Srivastava, R.M., 1989: An introduction to applied geostatistic. OxfordUniversity Press. New York. 561p.Mulla, D.J. and Hernández, J.A., 2006: On farm trials for precision agriculture. In:Congresso Brasileiro de Agricultura de Precisão, 2. São Pedro. Anais... Piracicaba: USP:ESALQ. 1CD-ROM.National Research Couneil (NRC), 1997: Precision Agriculture in the 21st Century:Geospatial and Information Technologies in Crop Management. National Academy Press,Washington, DC. 147p.Prado, R.M., 2001: Saturação por bases e híbridos de milho sob sistema plantio direto.Scientia Agrícola, v.58, n.2, p.391-394.Proceedings - CIEC 2009 267

Site specific soil fertility management of an oxisol cultivated with corn for application of lime and gypsum.

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