Study on two associated frut tree crops take up their N in comparison to a leguminous cover crop in an agroforestry system. Preliminar results showed the pueraria had the highest foliar N content followed by pupunha; cupuacu having less than the other two. One year after application, cupuacu took up more of the applied N in comparison to the total N uptake than pueraria and pupunha as seen from the high &15N values. The amount of 15N taken up in relation to dry matter equaled between the three species, since pueraria had a lot higher N contents. The other sampling dates showed the same tendency.bitstream/item/181065/1/ID-2600-2-45-52.pd

GEBAUER, G.

LEHMANN, J.

SILVA JUNIOR, J. P. da

SILVA, L. F. da

English

Study on two associated frut tree crops take up their N in comparison to a leguminous cover crop in an agroforestry system. Preliminar results showed the pueraria had the highest foliar N content followed by pupunha; cupuacu having less than the other two. One year after application, cupuacu took up more of the applied N in comparison to the total N uptake than pueraria and pupunha as seen from the high &15N values. The amount of 15N taken up in relation to dry matter equaled between the three species, since pueraria had a lot higher N contents. The other sampling dates showed the same tendency

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.995w'82002.00231Water and nutrient fluxes as1998 RT-2002.002311111111 IIIII IIIII 111111111111111IIII 11112600 - 2457) Nitrogen use of a mixed tree crop plantation with a leguminouscover cropJohannes Lehmann, Jose Pereira da Silva Jr., Gerhard Gebauer and Luciana Ferreira daSilvatntroducâonIn mixed tree crop plantations, the leguminous cover crop plays an important role for thereplenishment of N to the soil through biological nitrogen fixation. Apart from the N input,the cover crop also reduces the abundance of grasses which may compete with the treecrop for water and nutrients.It is not known, how much of their N trees take up from the area between the tree rows,where the biologically fixed N is mineralized from leaf and root litter of the legume.Furthermore, it is not clear, if deep or shallow rooted tree species are in the same wayable to utilize this N source and if they use fertilizer applied to adjacent tree crops.In this study, we adressed the question from where two associated fruit tree crops take uptheir N in comparison to a leguminous cover crop in an agroforestry system. The centralhypothesis is that tree crops benefit significantly from biologically fixed nitrogen of anintercropped legume.Materiais and methodsExperimental design and treatmentsIn this study, Bactris gasipaes (pupunha or peachpalm, Arecaceae) and Theobromagrandiflorum (cupuacu, Sterculiaceae), and a cover crop of Pueraria phaseoloides(pueraria, Fabaceae) were investigated in an agroforestry combination on a chromicFerralsol. Cupuacu and pupunha were planted in rows with 5 m distance, leaving 6 mbetween cupuacu and 2 m between pupunha within the rows. The pupunha was managedfor palmito pruduction (heart of palm) and cut every 4-5 months. Pueraria was sownbetween the trees.Applicafion of 15N46Within the plots of 48x32, microplots were chosen with two pupunha and one cupuacutree in three replicates (Figo 1)0 At times of regular fertilisation at the beginning ofDecember 1997 and at the end of April 1998, 15N was applied as (NH4)2S04 in aqueoussolution with 10 atom % excess 15N at a rate of 10 kg N ha-1 using a manual sprayer. The15N enriched fertiliser was not added uniformly to the plots but in three differenttreatments either under the cupuacu, the pupunha or the pueraria. This procedureresulted in a higher concentration of 15N per area under the cupuacu (105 g15N m-2) thanthe pupunha (005 g15N m-2) and the pueraria (0014 g15N m-2), as the area occupied bythese plant species increased in the same direction with 1, 3 and 11 m2 , respectively(Figo 1)0 The main plots (application to the different plants) were arranged in a randomizedcomplete block design, the subplots (plant species) as a split plot (Little and Hills, 1978)0I3+-1--+t1tPU··--------5-------~~Figo 1 Layout of the experiment, circles show positions of cupuacu in area CP andpupunha in area PP; 15N was applied either in CP, PP or PU area (CP cupuacu, PPpupunha, PU pueraria); distances in [m].47Plant and sai! samplingThe N isotope composition was measured in the different plant species on 15 February,15 April, 14 May, 1 June and 14 September 1998 and in the soil at 0-0.1,0.1-0.3,0.3-0.5and 0.5-1.0 m depths only on 15 April 1998. From February to June, only the youngestfully developed leaf was sampled, only the middle leaflets of pupunha but the wholeleaves of cupuacu and pueraria. No significantly different N isotope composition existedbetween the youngest leaves and the whole plant of pueraria, therefore only the results ofthe latter are shown here. In November, a mixture of the whole standing biomass wasobtained sampling leaves, branches and stem.Natural 15N abundanceIn a second experiment, the youngest fully developed leaves were taken from cupuacuand pueraria, the middle leaflets from the youngest fully developed leaves of pupunha inthe agroforestry systems described above (P1), and an agroforestry system of cupuacuand pupunha together with Berthalletia excelsa and Bixa arellana (P2) with the sameplanting density of pupunha and cupuacu than in P1. The different systems had differentamounts of ground cover with pueraria: system P1 showed thick coverage, whereas P2was scarcely covered. The foliar N isotope composition was measured in the differentcrops at the end of the dry season in November 1997, and at the end of the wet season inJune 1998, and in the soil at 0-0.05 m depths on 15 November 1997 and 15 Apri11998.AnalysesThe leaf samples were dried at 70°C for 48 hours. The soil samples were air dried.Afterwards, they were finely ground with a ball mill. Ali samples were analysed using anElemental Analyser (Carlo Erba NA 1500) for Dumas combustion connected to an isotopemass spectrometer (FINNIGAN MAT delta E) via a split interface.The analyses of variance was computed using a split plot design (ANOVA of STATISTICAVersion 5). In case of significant effects or interactions, individual cell means on therespective levei were compared using LSD at p<0.05 (Little and Hills, 1978).48Results and DiscussionAreas of N uptakePueraria had the highest foliar N eontent followed by pupunha, eupuaeu having less thanthe other two (Table 1). One year after applieation, eupuaeu took up more of the applied Nin eomparison to the total N uptake than pueraria and pupunha as seen from the high Õ15Nvalues (Table 1). The amount of 15N taken up in relation to dry matter equaled betweenthe three species, sinee pueraria had a lot higher N eontents. The other sampling datesare not demonstrated here, but showed the same tendeney.The pereentage of 15N uptake between the three areas of application was always highestat the respeetive plant area, i.e. eupuaeu took up most of its N from underneath theeanopyete. Cupuaeu tended to take up more N from the area under pueraria (PU) thanthe pupunha (PP; Table 1). This was also seen from other sampling times, where thedifferenee proved to be signifieant (data not shown).The importanee of the eropping area for N uptake ean be seen from the 15N area uptakewhieh is the produet of the relative uptake in pereent and the area respeetive (Table 1).For eupuaeu, the area under pueraria (PU) is more important on the whole than the areaunderneath the eanopy (CP).Table 1 Biomass N eontent, N-isotope eomposition and proportion of 15N uptake from different areas inagroforestry with eupuaeu, pupunha and pueraria at the end of the dry season in November 1998, six monthsafter applieation of 15N at the beginning of May 1998; values in one eolumn followed by the same letter are notsignificantly different at p<0.05 (eomparison only within same plant parts; n=3).Speeies 15N plant part N Õ15N 15N amount 15N uptake 15N area uptakeapplieation eontentin area [mg g-l] [%0] [~g15Nexcess g-l] [%] [%15Nuptake %area]Cupuacu CP leaves 18.6 361 a 23.8 a 80.8 a 538 edbranches 4.7 235 a 4.0 b 77.7 a 518 edstem 3.8 296 a 4.0 b 64.2 a 428 bPP leaves 18.5 9d 0.3 b 1.1 e 22 dbranehes 5.6 23 cd 0.4 b 5.8 be 117 dstem 3.7 74 be 1.0 b 14.0 b 281 bPU leaves 18.0 81 ed 5.0 b 18.2 b 1331 bbranehes 4.1 55 c 0.9 b 18.4 b 1205 abstem 4.3 99 be 1.7 b 21.8 b 1599 aPupunha CP leaves 35.6 8d 0.4 b 1.6 e 11 dbranehes 5.8 5d 0.0 b 1.7 e 11 dstem 13.5 8e 0.1 b 2.6 c 18 bPP leaves 32.0 196 b 21.9 a 85.0 a 1700 bbranehes 6.3 121 b 2.7 b 83.4 a 1668 astem 22.4 107 b 8.1 b 76.4 a 1527 aPU leaves 33.3 36 d 4.2 b 13.4 be 982 bebranehes 5.3 23 c 0.3 b 14.9 b 1093 bestem 18.3 32 be 1.6 b 21.0 b 1543 aPueraria CP whole plant 40.3 11 d 0.9 b 3.2 e 21 dPP whole plant 39.7 68 cd 8.8 b 21.8 b 434 edPU whole plant 39.6 153 be 21.3 a 75.1 a 5508 aTable 2 Above ground biomass and 15Nuptake from different areas in agroforestry with cupuacu, pupunha and pueraria at the end of the dryseason in November 1998, six monthsafl~élPplLcéltion of 15N at the beginning ofMay 1998; means and standard errors (n=3).Species 15 1N appl. p ant partm areab' bi 15 15iomass iomass N uptake N uptake[kg tree~l] [Mg ha-I] [mgl5Nexcess tree"] [gl5Nexcess ha"]Cupuacu CP leaves 13.3 ±2.8 2.22 ±O.47 305.5 ±51.1 203.7 ±34.0branches 11.5 ±4.0 1.92 ±O.67 47.1 ±17.2 31.4 ±11.5stem 7.2 ±l.l 1.20 ±O.18 30.0 ±8.9 20.0 ±5.9whole plane 32.0 ±7.5 5.33 ±1.24 382.6 ±72.7 255.0 ±48.5PP leaves 10.1 ±2.6 1.69 ±O.43 3.3 ±1.8 2.2 ±1.2branches 7.5 ±1.7 1.25 ±O.28 2.4 ±O.8 1.6 ±O.6stem 4.5 ±O.8 0.76 ±O.13 3.9 ±1.4 2.6 ±O.9whole plane 22.2 ±4.8 3.70 ±O.81 9.6 ±1.7 6.4 ±l.lPU leaves 10.5 ±3.7 1.75 ±O.62 50.3 ±14.3 33.5 ±9.5branches 8.6 ±3.0 1.43 ±O.49 8.1 ±5.1 5.4 ±3.4stem 5.9 ±1.7 0.99 ±O.28 8.4 ±2.7 5.6 ±1.8whole plant' 25.0 ±8.3 4.16 ±1.38 66.7 ±19.8 44.5 ±13.2Pupunha CP leaves 0.9 ±O.l 0.45 ±O.O4 0.4 ±O.O 0.5 ±O.lbranches 1.1 ±O.l 0.54 ±O.O5 0.0 ±O.O 0.1 ±O.Owhole plant' 2.0 ±O.2 0.99 ±O.O9 0.4 ±O.O 0.5 ±O.lwhole plane 1.9 ±O.3 ± ±PP leaves 1.3 ±O.4 0.63 ±O.19 31.1 ±17.5 41.5 ±23.3branches 1.5 ±O.4 0.75 ±O.22 4.5 ±2.5 6.0 ±3.4whole plant' 2.7 ±O.8 1.37 ±O.41 35.6 ±20.0 47.5 ±26.7whole plane 1.4 ±O.3 ± ±PU leaves 1.6 ±O.3 0.79 ±O.13 6.1 ±4.0 8.1 ±5.3branches 1.9 ±OJ 0.94 ±16 0.7 ±O.3 0.9 ±O.4whole plant' 3.5 ±O.6 1.73 ±O.29 6.8 ±3.8 9.0 ±5.1whole plane 2.1 ±O.2 ± ±Pueraria CP whole plane - 21.93 ±O.32 - 20.2 ±7.4PP whole plane - 21.93 ±O.32 - 44.8 ±lO.3PU whole plane - 21.93 ±O.32 - 467.2 ±37.1lcalculated from plant parts; 2 measured by direct harvesting and weighing; 3 calculated from direct harvesting and occupied area51Fertilizer efficiencyThe recovery of the applied 15N increased in the order pupunha<cupuacu<pueraria(Table 3). Despite the generally higher root abundance and more vigourous growthof the palm than cupuacu (Haag, 1997; Wolf, 1997), cupuacu took up more of theapplied N than pupunha.Five months after the 15Napplication, part of the applied N was leached down to 1m(Fig.1). Pueraria took up most of the N from the topsoil, whereas under the trees the15N accumulated at 0-0.1 m. A significantly larger portion of the applied Naccumulated at 0.3-0.6 m under cupuacu than under the other two species. Puerariamay have been more efficient in taking up the 15N before it was leached, whereaspupunha may also have taken up leached nutrients from greater depth, sincepupunha has higher root activity also at 0.6 m than 0.1 m (Section 6: Fig. 2).Table 3 Recovery of 15N applied to different areas in agroforestry with cupuacu,pupunha and pueraria at the end of the dry season in November 1998, six monthsafter application of 15Nat the beginning of May 1998; values in one column or rowfollowed by the same small or capital letter, respectively, are not significantlydifferent at p<0.05; means and standard errors (n=3).Species recovery [%] of 15Napplied atcupuacu pupunha pueraria0.32 b ±O.O6 2.22 b ±O.66C B2.37 a ±1.33 0.45 c ±O.25A B2.24 a ±O.51 23.36 a ±1.85B Atotal areaCupuacu 12.75 a ±2.42A15.30 b ±2.89Pupunha 0.03 c ±O.OOC2.85 c ±1.59Pueraria 1.01 b ±O.37B26.61 a ±2.09organic carbon [mg g-1] nitrogen [mg g-1]o 10 20 30 40 O 1 2 3 4o'-' ns-10 a>-l nsE -30~ H nss:-aCD -50 cupuacu"t:lpupunhapuerariaf-< ns-100Õ15N 15Namount [Ilg 15Nexcess 9-1]o 20 40 60 80 0,0 0,2 0,4 0;6 0,8o>---< *-10 CH *E -30~s: f--I ** H*-aCD -50.">----<nsJH ns-10052Fig_ 2 Soil carbon and nitrogen contents and 15N enrichment under cupuacu,pupunha and pueraria five months after application of 15N in November 1997; onlysites where 15N was applied; asterics denote significant effects at p<O_OS* and 0_01** (ANOVA); means and standard errors (n=3)_Nitrogen benefit trom N2 fixationPueraria posseses higher N contents and lower Õ15N values than the two treespecies, indicating biological fixation of atmospheric N2- The Õ15N values of cupuacuand pupunha are slightly lower in P1 than P2_This may be interpreted as a transferof biologically fixed N2 from the pueraria to the trees. The total N contents, however,did not increase and the differences of the Õ15N values were not significantTherefore, the contribution of fixed N of the pueraria to the N nutrition of theassociated trees was not very high_53Table 4 Foliar nitrogen and natural 15N abundance of cupuacu, pupunha andpueraria in an agroforestry system with high (P1) and low (P2) abundance ofpueraria; means and standard errors (n=3).Species System End of dry season End of wet seasonN Õ15N N Õ15N[mg g-1] [%o] [mg g-1] [%o]Cupuacu P1 17.74 ±O.52 4.06 ±O.55 14.82 ±O.51 4.08 ±O.33Cupuacu P2 17.35 ±O.74 4.64 ±O.53 14.10 ±O.95 4.70 ±O.81Pupunha P1 28.91 ±O.46 4.90 ±O.48 37.34 ±4.87 5.02 ±O.59Pupunha P2 31.80 ±1.51 5.19 ±O.20 34.85 ±2.47 6.83 ±O.18Pueraria P1 43.52 ±O.55 2.16 ±O.O8 44.26 ±2.35 1.72 ±2.15Pueraria P2 38.71 ±O.54 2.75 ±O.33 37.13 ±2.02 0.97 ±1.95ReferencesHaag O, Schroth G, Villani E and Zech W 1998 Complementary strategies of soilexploration by the roots of Amazonian tree crops in agroforestry on an acid uplandsoil. Agrofor Syst: submitted.Little T M and Hills F J 1978 Agricultural Experimentation. Wiley and Sons, NewYork, USA. 350p.Wolf MA 1997 Accumulation of biomass and nutrients in the aboveground organs offour local tree species in mono-culture and polyculture systems in central Amazonia.MSc Thesis, University of Braunschweig, Germany.

Nitrogen use of a mixed tree crop plantation with a leguminous cover crop.

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Nitrogen use of a mixed tree crop plantation with a leguminous cover crop.

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