Introduction. Department of Soil Science, Faculty of Agriculture, Kasetsart University, Bangkok * Corresponding author:

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1 KHO แก นเกษตร KAE 45 AGR. (2) J. : (2) : (256). (217). KHO KAE AGR. J. 45 (2) : (217). 373 The impcts of tillge, soil conditioners, nd chemicl fertilizer on yield of cssv in Ysothon Soil Series (Typic Pleustult), reltionship between nutrient concentrtion nd cssv yield components, nd soil property Piltluck Lunlio 1, Somchi Anusontpornperm 1*, Suphich Thnchit 1 nd Irb Kheoruenromne 1 ABSTRACT: A study ws conducted in frmer field t Bn Supplu oi, Huy Bong subdistrict, n Khun Thot district, kon Rtchsim. Cssv, Huy Bong 8 vriety, ws plnted in Ysothon soil series clssified s Typic Pleustult. Split-split plot in RCB ws employed with four replictions. Min plot consisted of norml () nd deep tillge (). Subplot contined 11 tretments, T1: no soil conditioner pplied, nd pplying respective rtes of 625 nd 1,25 kg/h of soil conditioners such s bentonite (T2 nd T3), perlite (T4 nd T5), gypsum (T6 nd T7), dolomite (T8 nd T9), nd ground limestone (T1 nd T11). Sub-subplot ws performed with two rtes of chemicl fertilizer; (L) nd 625 (H) kg/h. Soil representing the experimentl re ws clssified s Typic Pleustult. Cssv ws hrvested t 1-month of ge. ifferent plnt prts of cssv were smpled during the hrvesting time for the nlysis of nutrient concentrtion. Results showed tht deep tillge highly significntly promoted higher fresh tuber yield (FTY) of t/h nd strch yield (STY) of 7.77 t/h thn did norml tillge (25.61 nd 6.93 t/h, respectively) but hd no different effects on strch content (STC) nd boveground biomss (ABG). The ppliction of dolomite (T8) significntly gve the highest FTY, STY nd ABG of 31.68, 8.65 nd 1.97 t/h, respectively. Cssv did not respond to rtes of chemicl fertilizer differently. However, there were some interctions between tillge nd chemicl fertilizer tht ffected cssv yield components. There were positive correltions between plnt nutrient concentrtions, especilly mcronutrient in stem, with FTY nd ABG. Both rtes of dolomite (T8 nd T9) nd ground limestone (T1 nd T11) induced higher soil ph thn did other soil conditioners nd the control. Furthermore, the ppliction of some soil conditioners contributed higher vilble P, K nd Mg contents remined in the soil fter growing cssv for one crop. Keywords: Plough Pn, Tillge Prctice, Soil Conditioner, Cssv, orthest Thilnd Introduction Cssv (Mnihot esculent Crntz.) is considered one of the most importnt economic crops in Thilnd of which the country is the leding cssv exporter of the world. Plnting re of cssv in Thilnd in 215 ws round 1.49 million h. A mjor cssv plnting re is in the northest, ccounting for pproximtely.78 million h. However, the verge yield of cssv in this region is lower thn in other regions (Office of Agriculturl Economics, 216). Most cssv growing soils in the northest hve sndy lom to corser texture, possessing low griculturl potentil, low fertility, wek structure, moderte to excessive dringe nd high rte of leching (Howeler, 1981; Rtnwrh et l., 1997; Anusontpornperm et l., 29). Plough pn is one of mjor problems in these cssv growing soils in the region (Anusontpornperm et l., 25; Kliklom et l., 21; Meewssn et l., 21). Hmz nd Anderson (22) found tht deep ripping lone incresed the infiltrtion rte in the first three yers but the effect did not lst into the fourth yer. There re some reports showing tht subsoiling by using ripper gve significntly higher fresh tuber yield thn did the other without using ripper (18.25 compred to t/h) (Riyphn et l., 21). Using ripper to brekdown plough pn gve fresh tuber yield of t/h, which ws significntly higher thn tht of without 1 eprtment of Soil Science, Fculty of Agriculture, Ksetsrt University, Bngkok 19 * Corresponding uthor: somchi.@ku.c.th

2 374 แก นเกษตร 45 (2) : (256). rippering (28.94 t/h) in the first yer but the effect ws to no vil in the following yer (Sukswt et l., 21). This indicted tht the efficiency of ripper lsted only one yer nd is of the cse ccording to the study of Kewkmthong et l. (214). Uses of soil conditioners for improving the soils in this region hve been studied (ungptr, 1988). For instnce, ground limestone nd dolomite tht re rich in clcium cn increse soil ph nd vilble phosphorus (Riyphn et l., 21; Promm et l., 212) nd lso improve soil structure, especilly in reducing compction (ungptr, 213). The ddition of ground limestone, dolomite nd gypsum on Ysothon soil incresed fresh tuber yield of cssv, number of tuber/plnt, bove ground biomss, nd strch content, prticulrly more clerly in the second yer (Promm et l. 212). As results of using ripper to brekdown plough pn tht helped improve yield of cssv only in the first yer, this study ws undertken with the ims t investigting the impct of tillge, soil conditioners nd chemicl fertilizer on yield, nd correltions between nutrient concentrtion nd yield components of cssv grown on Typic Pleustult, which is mjor cssv soils in the northest (Anusontpornperm et l., 29) nd to exmine soil properties s ffected by these prctices. Mterils nd Methods The experiment ws crried out in frmer field t Bn Spplu oi, Huy Bong subdistrict, n Khun Thot district, kon Rtchsim province during ovember 212 nd October 213. The experimentl site ws undulting with 5% slope nd elevtion of 38 m bove MSL. The verge nnul rinfll nd temperture t the site were 1,36. mm/yr nd 27.6 C, respectively. The soil ws developed on locl lluvium over residuum derived from sedimentry rock minly conglomerte nd sndstone, hving well-drined feture with rpid permebility nd runoff. This soil ws clssified s Typic Pleustult (Ysothon soil series). Generl soil properties re presented in Tble 1. Properties of soil before plnting, obtined from the nlysis of composite smple collected from -3 cm from experimentl plots, showed tht the soil ws composed of very low mounts of (.21 g/ kg), vilble P (1.9 mg/kg), vilble K (28.5 mg/ kg) nd extrctble C, Mg nd K (.94,.25 nd.7 cmol c /kg, respectively) with very low ction exchnge cpcity (.21 cmol c /kg). Split-split plot in rndomized complete block design were employed with four replictions. The min plot consisted of norml tillge () nd deep tillge () with the first plough using 3-disc plough operted to depths of 25-3 nd 45-5 cm, respectively. Subplot contined 11 tretments; T1: no ppliction of soil conditioner, nd ll the rest pplying two respective rtes of 625 nd 1,25 kg/ h of different soil conditioners such s bentonite (T2 nd T3), perlite (T4 nd T5), gypsum (T6 nd T7), dolomite (T8 nd T9), nd ground limestone (T1 nd T11). Sub-subplot comprised two rtes of chemicl fertilizer, (312.5 (L) nd 625 (H) kg/h). Cssv, Huy Bong 8 vriety, ws plnted on ridges with spcing of.8 m between plnts nd 1.2 m between rows nd hrvested t 1 months of ge. Plnt nd soil smples were tken t the time hrvest for nlyses of nutrient concentrtion nd soil properties, respectively. Site chrcteriztion of the experimentl re ws crried out ccording to stndrd field methods. Cssv yield, mesured plnt components, nd soil properties were compred mong tretments using the nlysis of vrince for sttisticl significnce, nd men seprtion ws done using SPSS progrm nd uncn s multiple rnge test (MRT) with differences being tested t.1 nd.5 level of significnce.

3 KHO KAE AGR. J. 45 (2) : (217). 375 Tble 1 Physicl nd chemicl properties of Typic Pleustult (Ysothon soil series), representtive soil of the experimentl re. epth Hor. ph 1/ OM 2/ Extrctble bse 3/ CEC 4/ BS 5/ B 6/ Kst 7/ Texture 8/ 1:1 C Mg K (cm) H 2 O (g/kg) ( cmol c /kg ) (%) (Mg/m 3 ) (cm/hr) -15/17 Ap LS 15-3 Bt SL 3-65 Bt SL 65-9 Bt LS Bt SL Bt SL Bt SL Bt SL Bt SL Hor. = horizon, OM = orgnic mtter, CEC = ction exchnge cpcity, BS = bse sturtion, B = bulk density, Kst = hydrulic conductivity, LS = lomy snd, SL = sndy lom 1 ph (H 2 O), 2 Wlkley nd Blck, 3 1M H 4 OAc t ph 7., 4 1M H 4 OAc t ph 7., 5 1M H 4 OAc t ph 7., 6 Core method, 7 vrible hed method, 8 pipette method Results nd discussion compction nd help re-forming the structure of tilled soil, binding or flocculting gent (lime, Effects of tillge, soil conditioners nd chemicl gypsum or orgnic mtter) is needed. Without such fertilizer on cssv fresh tuber yield, strch content, strch yield nd boveground biomss son, 22; 23) sometime in the first yer fter gent compction cn recur (Hmz nd Ander- eep tillge to the depth of 45-5 cm () tillge (Mofft nd Boswell, 1996). Hll et l. (1994) highly significntly gve higher fresh tuber yield of reported tht the effect of deep tillge on soil-wter t/h nd strch yield of 7.78 t/h thn did reltions declines fter the first yer nd yield increses ssocited with deep tillge did not persist norml tillge to the depth of 25-3 cm () tht hd both yields of nd 6.93 t/h, respectively beyond the second yer of the experiment, (Figure 1, c) while there ws no difference in presumbly due to re-compction. strch content nd boveground biomss (Figure The soil mended with dolomite t the rte of 1b, d). It cn be stted tht deep tillge tht took 625 kg/h (T8) significntly gve the highest fresh some of subsoil, which possessed some unfvorble properties such s low soil ph nd very low sttisticlly not different from those obtined from tuber yield of t/h. This mount of yield ws orgnic mtter content, to mix with topsoil did not plots mended with dolomite t doubling rte (T9), hve dverse effect of growing plnt. This opertion both rtes of ground limestone (T1 nd T11), nd my hve helped enhnce growth nd subsequently results in n increse of cssv yield s in the rnge of t/h. It ws cler tht bentonite t the rte of 625 kg/h tht gve the yield dense lyer directly beneth the topsoil ws destroyed. In ddition to tht, the movement of wter gve the lowest yield of t/h (Figure 1). growing cssv without the use of soil conditioner within soil profile would be more rpidly, resulting Similr trends were lso found in the cse of strch in reducing ccumultion of wter in the soil surfce yield nd boveground biomss (Figure 1c, d) tht nd subsequent runoff (Hssn et l., 27). Although, this result is yet to be sufficiently conclu- (T8) lso positively showed the gretest impct. the ppliction of dolomite t the rte of 625 kg/h sive, previous studies showed tht to prevent re- This coincides with Mnrique (1987) in which the

4 376 แก นเกษตร 45 (2) : (256). result showed positive nd significnt cssv yield response to liming strongly cid Ultisol with 6-11 t/h lime. In ddition, recent studies conducted on rther similr soils in the northest lso demonstrted better effectiveness of dolomite nd ground limestone used to condition the soil for growing cssv thn the others (Knjn et l., 212; Yimnoi et l., 214). It ws rther surprising tht different rtes of chemicl fertilizer dded did not give ny different yield components insted of the higher rte being twice higher. Although, Sittibusy (1996), bsed on results of lrge number of FAO-sponsored on-frm fertilizer trils, recommended lmost the sme mount s the higher rte (H) used in this experiment, the yield response did not come to term s expected. This might be due to the soil hving been severely degrded or mounts of mjor plnt nutrient required by cssv, Huy Bong 8 vriety, being different from those vrieties used in those trils. onetheless, there were no different effects of interctions between tillge nd soil conditioner, tillge nd chemicl fertilizer, nd soil conditioner nd chemicl fertilizer these yield components. Tillge Soil conditioner Fertilizer () Fresh tuber yield (t/h) (b) Strch content (%) (c) Strch yield (t/h) **, SEM=.643 *, SEM=1.59 ns, SEM= b -c 1 c bc c bc bc bc 5 -c bc b T1 T2 T3 T4 T5 T6 T7 T8 T9 T1 T11 L H 3 ns, SEM=.176 ns, SEM=.413 ns, SEM= b T1 T2 T3 T4 T5 T6 T7 T8 T9 T1 T11 L H **, SEM=.183 *, SEM=.43 ns, SEM= c bc bc bc bc bc bc T1 T2 T3 T4 T5 T6 T7 T8 T9 T1 T11 L H -c bc b (d) Aboveground biomss (t/h) ns, SEM=.277 *, SEM=.648 ns, SEM= c bc bc c bc bc bc T1 T2 T3 T4 T5 T6 T7 T8 T9 T1 T11 L H = orml tillge; = eep tillge; T1: no soil conditioner, T2 nd T3: bentonite 625 nd 1,25 = orml tillge; = eep tillge; T1: no soil conditioner, T2 nd T3: bentonite 625 nd 1,25 kg/h, T4 nd T5: perlite 625 nd 1,25 kg/ h, T6 nd T7: gypsum 625 nd 1,25 kg/h, T8 nd T9: dolomite 625 nd 1,25 kg/h, nd T1 nd T11: ground limestone 625 nd 1,25 kg/h, L nd H = Chemicl fertilizer nd 625 kg/h; common letters on the top of brs re not significntly different; no letter on the top of brs shows no significnt difference Figure 1 Effects of tillge, soil conditioners nd chemicl fertilizer on cssv fresh tuber yield, strch content, strch yield nd boveground biomss bc bc b

5 KHO KAE AGR. J. 45 (2) : (217). Effects of tillge, soil conditioners nd chemicl fertilizer on the reltionships between plnt nutrient concentrtion nd cssv yield components Person correltion coefficient (2-tiled) ws done to estblish reltionships between nutrient concentrtion nd cssv yield components (Tble 2). Phosphorus concentrtion in tuber positively correlted with boveground biomss (r =.2**) while Mg concentrtion significntly showed negtive correltion with boveground biomss (r = -.15*). In stem bse, P concentrtions hd highly positive correltions with fresh tuber yield (r =.37**), strch yield (r =.36**) nd boveground biomss (r =.3**). In stem, P concentrtions highly positively correlted with fresh tuber yield (r =.27**), strch yield (r =.26**) nd boveground biomss (r =.23**). itrogen concentrtions in this plnt prt lso positively correlted with fresh tuber yield (r =.18*), strch yield (r =.18*) nd boveground biomss (r =.15*). Potssium concentrtions highly significntly hd positive correltions with fresh tuber yield (r =.22**) nd strch yield (r =.23**). Moreover, C concentrtions highly positively correlted with fresh tuber yield (r =.21**), strch yield (r =.22**) nd hd positive correltion with boveground biomss (r =.15*). There were positive correltions between Mg concentrtions nd fresh tuber yield (r =.16*) nd strch yield (r =.16*). In lef nd brnch, there were only some micronutrients tht hd correltions with yield components. Mngnese concentrtion hd positive correltions with fresh tuber yield (r =.18*), strch yield (r =.19*) nd boveground biomss (r =.2**) while Cu concentrtion positively correlted with boveground biomss (r =.2**). 377 Considering fresh tuber yield, P concentrtions in stem bse nd stem,, K, C nd Mg concentrtions in stem nd Mn concentrtion in lef nd brnch showed positive correltions to different degrees. This indicted tht the increse of these nutrients concentrtion in boveground plnt prt hd the effect on incresing cssv fresh tuber yield. In the cse of strch yield or in the other word, the qulity of cssv tuber, there were P concentrtion in tuber, ll mjor plnt nutrients in stem including C nd Mg, nd Mn in lef nd brnch tht hd the correltion with strch yield. This cn be indictive of the plnt with substntil mounts of mcronutrients stored in the stem prt being likely to give stisfctory strch yield. Among these correltions found in the study, P ws the most common, thus mngement of P fertiliztion is vitl in terms of improving yield of cssv, Huy Bong 8 vriety, grown on this Typic Pleustults, of which this initil content of it vilble form before plnting ws very low ( mg/kg). Phosphorus in lef nd brnch, stem nd stem bse usully promotes root growth nd plys n importnt role in energy trnsformtions nd metbolic processes in plnts. It is essentil for photosynthesis nd crbohydrte synthesis, hence importnt for tuberiztion. Cssv is found to be inefficient in P uptke though it grows well in low P soil nd cssv s response to P hs usully been minor (John, 21). Improvement in qulity of cssv due to increse in strch yield nd decrese in cynogenic glycoside content s result of higher levels of P nutrition were reported by John et l. (25). Appliction of P up to 1 kg/h P 2 O 5 enhnced strch yield nd reduced HC content. Moreover, significnt reduction in HC content, incresing in dry mtter, strch nd crude protein contents due to P fertiliztion (John et l., 26).

6 378 แก นเกษตร 45 (2) : (256). Tble 2 Correltions between nutrient concentrtion in vrious prts of cssv nd cssv yield components Concentrtion Person s r (=176) Tuber P K C Mg S Fe Mn Zn Cu FTY STC STY ABG.13.2** * Stem bse P K C Mg S Fe Mn Zn Cu FTY.7.37** STC STY.3.36** ABG.11.3** Stem P K C Mg S Fe Mn Zn Cu FTY.18*.27**.22**.21**.16* STC STY.18*.26**.23**.22**.16* ABG.15*.23**.11.15* Lef nd brnch P K C Mg S Fe Mn Zn Cu FTY * STC STY * ABG **.2.21** FTY: fresh tuber yield, STC: strch content, STY: strch yield, ABG: boveground biomss * significnt correltion, ** highly significnt correltion The other two mjor plnt nutrients, nd K, lso showed correltion between their concentrtion in stem nd cssv yield. itrogen is the second nutrient, fter potssium, most used by cssv (Howeler, 22, 214; Ayool nd Mkinde, 27) in some cses. itrogen generlly promotes growth, improves the efficiency of photosynthesis, increses lef re index (LAI) nd increses the yield (Howeler, 22; 214). Lrge nitrogen pplictions cn lso likely to reduce the hrvest index (HI), root yield nd strch content while incresing the HC content of the root (Edwrds nd Kng, 1978). The positive correltion found here indicted tht the increse of this nutrient, especilly in the stem cn possibly increse fresh tuber nd strch yields. This ws lso the cse for K s shown by its concentrtion in stem with fresh tuber nd strch yields in which this nutrient in stem besides incresing the overll yield improves dry mtter, strch yield nd reduces HC content. Appliction of K t 1 kg/h K 2 O produced higher tuber yield with high percentge strch yield nd low HC content (ir nd Aiyer, 1986). Effects of tillge, soil conditioners nd chemicl fertilizer on soil chemicl property The use of dolomite t the rte of 1,25 kg/ h (T9) to condition the soil highly significntly induced the highest soil ph of 6.34 (Figure 2). The vlues were lso higher thn tht of the plot mended with the lower rte of the sme mteril. Ground limestone lso lifted soil ph when compred to other soil conditioners such s bentonite, perlite nd gypsum nd the control with no ppliction of soil conditioner. This is becuse lime (CCO 3 ) ws effective in rising soil ph (Liu nd Hue, 211). olomite nd ground limestone hd the effect on reducing soil cidity level in corse-textured soil nd contined high mount of bses such s C nd Mg, which cn serve to reduce soil cidity (Redly nd Utkev, 29) wheres bentonite, perlite nd gypsum re not lime mteril used for reducing soil cidity. The

7 KHO KAE AGR. J. 45 (2) : (217). results of this study gree with those obtined by Mkrim et l. (1989) nd Cssel et l. (199) in West Sumtr. These results reveled tht lrge quntities of lime nd commercil fertilizers were needed for rpid reclmtion of cid, infertile soil. In ddition, lime provides C 2+ nd genertes OH - ions tht neutrlize the cidity, thus rising the ph (Peregrin et l., 26). All prctices hd no effect on soil orgnic mtter content which the mounts (4.8 nd 4.33 g/hg) remined in the soil were still very low (Figure 2b). The mounts of soil orgnic mtter s ffected by soil conditioners pplied were in the rnges of g/kg. The soil mended with bentonite t the rte of 625 kg/h (T2) 379 significntly gve the highest vilble phosphorus of 1.23 followed by 9.97 mg/kg being from the plot mended with the sme soil conditioner t doubling rte (T3). It cn be noticed tht the lowest mounts of vilble phosphorus left in the topsoil were in the control plot with no ppliction of soil conditioner. orml plcement of bentonite t the rte of 1,25 kg/h (T2) significntly gve the highest vilble phosphorus of 1.54 mg/kg left in the topsoil (Figure 2c). ifferent depths of tillge with no ddition of soil conditioner (T1 nd T1) evidently resulted in the lowest mounts (7.26 nd 6.64 mg/kg) of vilble phosphorus remined in the soil. Tillge Soil conditioner Fertilizer 6 ns, SEM=.21 **, SEM=.5 ns, SEM=.21 () ph 1:1 (H2O) 4 2 ef f c-f c-e cd d-f b-d b bc b T1 T2 T3 T4 T5 T6 T7 T8 T9 T1 T11 L H (b) OM (g/kg) ns, SEM=.94 ns, SEM=.22 ns, SEM=.94 T1 T2 T3 T4 T5 T6 T7 T8 T9 T1 T11 L H (c) Avil. P (mg/kg) ns, SEM=.222 ns, SEM=.521 ns, SEM=.222 b b b b b b c bc b T1 T2 T3 T4 T5 T6 T7 T8 T9 T1 T11 L H 2 *, SEM=.886 **, SEM=.886 *, SEM=.378 (d) Avil. K (mg/kg) b d d cd b-d -c cd b-d b b-d d T1 T2 T3 T4 T5 T6 T7 T8 T9 T1 T11 b L H 2 ns, SEM=4.76 ns, SEM=9.559 ns, SEM=4.76 (e) Avil. C (mg/kg) T1 T2 T3 T4 T5 T6 T7 T8 T9 T1 T11 L H Figure 2 Effects of tillge, soil conditioners nd chemicl fertilizer on soil chemicl property fter growing cssv for one crop

8 38 แก นเกษตร 45 (2) : (256). It ws evident tht tillge, soil conditioner nd chemicl fertilizer hd the effect on vilble potssium left in the topsoil. eeper depth of the first plough () sttisticlly resulted in greter mount of vilble potssium left in the soil thn did shllower depth () of the first plough, giving the vlues of compred to mg/kg (Figure 2d). Applying ground limestone t the rte of 1,25 kg/h (T11) highly significntly gve the highest vilble potssium of 2.1 mg/kg followed by mg/kg which ws obtined from the soil mended with dolomite t the rte of 625 kg/h (T8). With no ppliction of soil conditioner (T1), vilble potssium left in the soil ws lowest. This might be due to ll soil conditioners either hve the bility to increse soil ph or contin ction exchnge cpcity to some extent, thus the ppliction subsequently contributes the bility of the soil to retin potssium. In ddition, rising soil ph cn increse CEC nd reduce leching of K but, unless K is incresed with lime, sorption nd vilbility of K my be incresed (von Uexkull, 1986). The ppliction of 625 kg/h (H) significntly promoted higher vilble potssium content thn did the ddition of kg/h (L), compred to mg/kg. In ddition, there ws the interction between tillge nd chemicl fertilizers of which deep tillge long with the ddition of 625 kg/h highly significntly gve the highest vilble potssium of mg/kg left in the topsoil. Moreover, the interction between soil conditioner nd chemicl fertilizers lso hd the influence on vilble potssium. Applying dolomite t the rte of 625 kg/h with the ddition of 625 kg/h (T8H) highly significntly resulted in the highest vilble potssium of 22.3 mg/kg remined in the topsoil fter hrvesting cssv. eep tillge t the depth of 4-5 cm () nd soil conditioner hd no effect on vilble clcium left in the topsoil (Figure 2e) nor different type nd rte of soil conditioners. Ritchey et l. (24) reported tht since only 34% of the C dded s dolomite ws extrcted from the surfce 15 cm, some of it my still hve not dissolved, or it my hve been solubilized by rections with cid rin or fertilizer nd leched below 15 cm with sulfte or nitrte ions, lost by erosion, tken up by plnts, moved downwrds by soil fun such s erthworms, or trnsformed into nonexchngeble forms. There were no different impcts of chemicl fertilizer, the interctions between tillge nd soil conditioner, tillge nd chemicl fertilizer, nd soil conditioner nd chemicl fertilizer on the content of vilble clcium remined in the soil. The reson for subsoil meliortion is to improve rooting depth by incresing subsoil permebility. The lime should be incorported in the soil s deeply s possible by plough or disc hrrow. It is becuse lime left on the soil surfce my, depending on soil s buffer cpcity nd mount of ph-dependent chrge, rect only with the surfce lyer (1-2 cm) of soil nd not relese C to move down the profile (Crswell, 1989). In the cse of vilble mgnesium, the ppliction of bentonite t the rte of 1,25 kg/h (T3) significntly gve the highest vilble mgnesium of 29.3 mg/kg followed by mg/kg obtined from the soil mended with perlite t the rte of 625 kg/h (T4) (Figure 2f). This might be coincidence s the control sttisticlly gve no different mount nd more noticebly the ddition of dolomite significntly showed lower mount in spite of this mteril contining the highest mount of Mg when compred to the others. Conclusions eep tillge to the depth of 45-5 cm clerly promoted greter fresh tuber nd strch yields of

9 KHO KAE AGR. J. 45 (2) : (217). cssv, Huy Bong 8 vriety, thn did norml tillge to the depth of 25-3 cm tht ws commonly operted by cssv growing frmers in the northest. The dditions of dolomite nd ground limestone to condition this Typic Pleustult (Ysothon soil series) were more effective considering fresh tuber nd strch yields obtined thn did the pplictions of bentonite, perlite nd gypsum. Growing cssv on this soil without using ny soil conditioner gve the lowest yield. Furthermore, using of dolomite nd ground limestone cn improve soil ph nd vilble P nd K contents remined in the topsoil fter growing cssv for one crop. In ddition, nutrient concentrtions positively correlted, to some degree, with cssv yield components, especilly the concentrtions of P in stem bse,, P, K, C nd Mg in stem, Mn in lef nd brnch with fresh tuber yield. Acknowledgment The uthors would like to thnk tionl Reserch Council of Thilnd (RCT) nd tionl Science nd Technology evelopment Agency (STA) for finncil support of this study. References Anusontpornperm, S., S. ortcliff, nd I. Kheoruenromne. 25. Hrdpn formtion of some corse-textured uplnd soils in Thilnd. p In: The Conference on Mngement of Tropicl Sndy Soils from Sustinble Agriculture. ovember 27-ecember 2, 25, Khon Ken, Thilnd. Anusontpornperm, S., S. ortcliff, nd I. Kheoruenromne. 29. Interpretbility comprison between Soil Txonomic nd Fertility Cpbility Clssifiction units: cse of some mjor cssv soils in northest Thilnd. Ksetsrt J. (t. Sci.) 43: Ayool, O.T., nd E.A. Mkinde. 27. Fertilizer tretments effect on performnce of cssv under two plnting ptterns in cssv-bsed cropping system in south west igeri. Res. J. Agri. Bio. Sci. 3: Cssel,.K., M.K. Wde, nd A.K. Mkrim Crop response to mngement of degrded Oxisol Site in West Sumtr. Soil Tech. 3: Crswell, E.T., nd E. Pushprjh Mngement of Acid Soils in the Humid Tropics of Asi. Austrlin Centre for Interntionl Agriculturl Reserch. ungptr, P Soil nd climtic chrcteriztion of mjor cssv growing res in Thilnd. p In: R.H. Howeler, nd K. Kwno. Cssv Breeding nd Agronomy Reserch in Asi. Oct 26-28, Proc. 2 nd Regionl Cssv Workshop, Ryong, Thilnd. ungptr P Soil Conditioners. Ksetsrt University publishing. Edwrds,.G., nd B.T. Kng Tolernce of cssv (Mnihot esculent Crntz) to high soil cidity. Field Crops Res. 1: Hll,.J.M.,.C. McKenzie,.A. McLeod, nd I.. Toolt Ameliortion of hrdsetting Alfisol through deep moldbord ploughing, gypsum ppliction nd double cropping. Soil Till. Res. 28: Hmz, M.A., nd W.K. Anderson. 22. Improving soil fertility nd crop yield on cly soil in Western Austrli. Aust. J. Agric. Res. 53: Hmz, M.A., nd W.K. Anderson. 23. Responses of soil properties nd grin yields to deep ripping nd gypsum ppliction in compcted lomy snd soil contrsted with sndy cly lom soil in Western Austrli. Aust. J. Agric. Res. 54: Hmz, M.A., nd W.K. Anderson. 25. Soil compction in cropping systems: A review of the nture, cuses nd possible solutions. Soil Till. Res. 82: Hssn, F.U., M. Ahmd,. Ahmd, nd M.K. Abbsi. 27. Effects of subsoil compction on yield nd yield ttributes of whet in the sub-humid region of Pkistn. Soil Till. Res. 96: Howeler, R.H Minerl utrition nd Fertiliztion of Cssv. Centro Interncionl e Agricultur Tropicl, Cli. Howeler, R. 22. Cssv minerl nutrition nd fertiliztion. P In: R. J. Hillocks, J. M. Thresh, nd A. C. Bellotti. Cssv: Biology, Production, nd Utiliztion. CABI Publishing, ew York. Howeler, R Sustinble Soil nd Crop Mngement of Cssv in Asi: A Reference Mnul. The Interntionl Center for Tropicl Agriculture (CIAT) nd The ippon Foundtion, Tokyo.

10 382 แก นเกษตร 45 (2) : (256). John, S.K., C.S. Rvindrn, nd J. George. 25. Long Term Fertilizer Experiments: Three ecdes Experience in Cssv. Technicl Bulletin Series o.45, Centrl Tuber Crops Reserch Institute. Thiruvnnthpurm. John, K.S, G. Suj, S. Edison, nd C.S. Rvindrn. 26. utritionl isorders of Tropicl Tuber Crops. Technicl Bulletin Series o.48, Centrl Tuber Crops Reserch Institute, Sreekriym, Thiruvnnthpurm. John, K.S. 21. ynmics of nutrients under cssv (Mnihot esculent Crntz) grown in n Ultisol of Kerl-A review. J. Root Crops. 36: Kewkmthong, Y., S. Thnchit, S. Anusontpornperm, nd W. Wiriykitnteekul Allevition of Soil Compction Problem for Growing Cssv on Typic Pleustult, orthest Thilnd. Asin J. Crop Sci. 6: Knjn,., S. Anusontpornperm, S. Tnchit, nd A. Suddhiprkrn Effects of Soil Conditioners on Yield nd Strch Content of Cssv Grown on egrded Ysothon Soils. The Proceedings of the 38 th Congress on Science nd Technology of Thilnd (STT38). Kliklom, O., S. Thnchit, S. Anusontpornperm, I. Kheoruenromne, nd L. Chinet. 21. Properties of plough pn in cssv nd sugrcne growing soils, Khon Ken province. Khon Ken AGR. J. 38: Liu, J., nd. V. Hue Amending subsoil cidity by surfce pplictions of gypsum, lime nd composts. Commun. Soil Sci. Plnt Anl. 32: Mkrim, A. K.,. K. Cssel, nd M. K. Wde Effects of lnd reclmtion prctices on chemicl properties of n cid, infertile Oxisol in West Sumtr. Soil Technology. 2: Murique, L.A Response of cssv to liming on strongly cid Ultisol of Pnm. Commun. Soil Sci. Plnt Anl. 18: Meewssn, E., S. Anusontpornperm, I. Kheoruenromne, nd A. Suddhiprkrn. 21. Chrcteristics of plough pn under cssv production res in khon Rtchsim province. Khon Ken Agr. J. 38: Mofft, A.J., nd R.C. Boswell The effectiveness of cultivtion using the winged tine on restored snd nd grvel workings. Soil Till. Res. 4: ir, P.G., nd R.S. Aiyer Effect of potssium nutrition on cssv strch chrcters. J. Root Crops 12: Office of Agriculturl Economics Agriculturl Sttistics of Thilnd 215. ivision of Informtion Mngement under Center for Agriculturl Informtion, Ministry of Agriculture & Co-opertives. Peregrin, F., J.S. Aris, R.O. Fernndez, P.G. Fernndez, nd R.E. Serrno. 26. Agronomic implictions of the supply of lime nd gypsum by-products to Plexerults from western Spin. Soil Sci. 171: Promm J., S. Anusontpornperm, S. Thnchit, I. Kheoruenromne, nd P. Petprpi Khon Ken Agr. J. 4: Rtnwrh, C.,. Sennrong, nd P. Suriypn Sttus of Cssv in Thilnd. p In: Implictions for Future Reserch nd evelopment. The Thi Tpioc Trde Assocition Report (Vrious Issues). Bngkok. Redly, M., nd V. F. Utkev. 29. Kinds of chemicl meliortion. P In Agriculturl lnd improvement: Ameliortion nd Reclmtion. Vol. II. Ritchey, K..,. P. Belesky, nd J. J. Hlvorson. 24. Soil properties nd clover estblishment six yers fter surfce ppliction of clcium-rich by-products. Aron. J. 96: Riyphn S., S. Thnchit, S. Anusontpornperm, A. Suddhiprkrn, nd P. Petprpi. 21. Khon Ken Agr. J. 38: Sittibusy, C Strtegies of eveloping Fertilizer Recommendtions for Field Crops. eprtment of Agriculture, Ministry of Agriculture nd Coopertives, Bngkok. Sukswt,., S. Thnchit, I. Kheoruenromne, nd S. Anusontpornperm. 21. Effect of tillge nd soil mendments on yield of cssv grown on corse-textured soils. The proceedings of the 36 th Congress on Science nd Technology of Thilnd (STT36). von Uexkull, H.R Efficient fertilizer use in cid uplnd soils of the humid tropics. FAO Fertiliztion nd Plnt utrition Bulletin 1. FAO. Rome. Yimnoi,., S. Anusontpornperm, nd S. Thnchit Effect of Lime Mterils nd Cssv Peel on Cssv Grown on Stuk Soil. The proceedings of the 4 th Congress on Science nd Technology of Thilnd (STT4).