CONSERVATION TILLAGE IMPROVES SOIL PHYSICAL PROPERTIES ON DIFFERENT LANDSCAPE POSITIONS OF A COASTAL PLAIN SOIL.

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1 CONSERVATION TILLAGE IMPROVES SOIL PHYSICAL PROPERTIES ON DIFFERENT LANDSCAPE POSITIONS OF A COASTAL PLAIN SOIL Frncisco J. Arrig* 1, Andre S. Biscro 2, Kipling S. Blkcom 1, Joey N. Shw 3, Edzrd vn Snten 3 nd Ted Kornecki 1 1 USDA-Agriculturl Reserch Service, Ntionl Soil Dynmics Lortory, Auurn, AL. 2 University of Cliforni Coopertive Extension, Lncster, CA. 3 Deprtment of Agronomy nd Soils, Auurn University, Auurn, AL. *frncisco.rrig@rs.usd.gov ABSTRACT Improved crop mngement is necessry due to rising production costs nd environmentl concerns. Sptil vriility of soil physicl properties cn significntly ffect mngement pproches. A study ws estlished in 2007 to determine the effect of mngement prctices nd lndscpe vriility on selected soil qulity prmeters (infiltrtion, ggregte stility nd totl C) of 22 cre field locted in the centrl Alm Costl Plin. The field ws divided into three zones - summit, ckslope nd ccumultion, using elevtion, electricl conductivity nd trditionl soil survey dt. Four mngement systems - conventionl system with (CT+M) or without (CT) diry mnure, nd conservtion system, consisting of strip-tillge nd winter cover crop, with (ST+M) or without (ST) diry mnure were estlished on corn (Ze mys L.)-cotton (Gossypium hirsutum L.) rottion in Infiltrtion, ggregte stility nd C content were generlly lower in CT. Mnure significntly incresed the C content (P 0.001), with n overll 62% increse in soil C content when mnure ws pplied to CT, nd 39% greter when pplied to ST. Infiltrtion ws gretest on the summit (5.7 in/h), followed y ckslope nd ccumultion zones (3.4 nd 2.8 in/h, respectively). No significnt differences (P = 0.69 nd 0.39, respectively) were found for ggregte stility nd cron etween zones. Conservtion tillge improved wter infiltrtion nd incresed soil C content, wheres mnure hs only incresed soil C content. INTRODUCTION Soil physicl properties ffect wter nd chemicl movement in the soil nd cn hve significnt impct on crop productivity nd the environment. Certin lndscpes cn hve significnt differences in soil physicl properties due to sptil vriility nd cn e the mjor cuse of sptil vriility in crop yields (Terr et l., 2005). Topogrphy is significnt fctor for soil differentition (Jenny, 1941). Conventionl tillge prctices in res with steep slopes cn led to erosion nd soil degrdtion. Additionlly, nutrient distriution within soil profile cn chnge with lndscpe position (Blkcom et l., 2005). Another importnt fctor is the sptil distriution of soil C, since soil C cn significntly ffect soil chemicl nd physicl properties. Lndscpe position plys n importnt role in C sequestrtion (Terr et l., 2005). Conservtion tillge prctices, such s non-inversion tillge (strip-tilling), cn enefit production systems of southestern United Sttes. Conservtion systems tht include strip-till nd winter cover crops cn increse the soil orgnic C content nd provide protective crop residue on the soil surfce. Therefore, the ojective of this work ws to determine the effect of mngement prctice nd lndscpe vriility on selected soil qulity prmeters of Costl Plin soil in Alm.

2 MATERIALS AND METHODS The study site ws locted on 22 cre field in the Alm Agriculturl Experiment Sttion s E.V. Smith Reserch Center, ner Shorter. The site hs mximum slope of 8% nd contins 9 soil mp units. The four mngement tretments studied were: conventionl tillge system (chisel- followed y disc-plow) with (CT+M) nd without (CT) mnure, nd conservtion tillge system (strip tillge) tht incorported the use of winter cover crops with (ST+M) nd without mnure (ST). These tretments were estlished in lte summer of 2000 on corn (Ze mys L.) nd cotton (Gossypium hirsutum L.) rottion tht hd oth phses of the rottion present ech yer. Winter cover crops for the conservtion tillge system included mixture of rye (Secle cerele L.) with lck ot (Aven strigos Schre.) used efore cotton, nd mixture of crimson clover (Trifolium incrntum L.) with white lupin (Lupinus lus L.) nd fodder rdish (Rphnus stivus L.) efore corn. Four strips per crop, with n verge length of 800 ft, were estlished cross the lndscpe. Ech strip contined one of the four mngement systems. These strips were further divided into cells to simplify smpling nd field mesurements. Six replictions were estlished on the 22 c field; ech repliction consisted of eight strips (four mngement systems x two crops). Four zones were estlished t the site y other reserchers using digitl elevtion mp, electricl conductivity survey nd trditionl soil mpping techniques (Terr et l., 2004). Three of these zones were selected (summit, ckslope nd ccumultion) for this study. Two cells per mngement nd zone were selected to conduct soil physicl properties chrcteriztion (Fig. 1). Accumultion N Bckslope Summit Figure 1. Mp of the zones in the reserch site nd the smpling cells used in this study. The green zone in the northern section of the field is n intermedite trnsitionl zone not included in this reserch. Soil properties studied included totl soil C y dry comustion t three depths, wter infiltrtion with mini-disk infiltrometer, nd wter stle ggregtes (Nimmo nd Perkings, 2002). Other

3 dt were collected, including soil ulk density nd wter retention, ut will not e presented here. Dt were nlyzed with the MIXED model procedure in SAS (SAS Institute Inc., Cry, NC). Mngement system, lndscpe position, depth, nd their interctions were considered s fixed effects. RESULTS AND DISCUSSION Totl C ws gretest in the ST+M followed y CT+M, ST, nd CT from 0-2 in of depth (Tle 1). Soil C content ws only ffected y tillge t the 0-2 in depth, where totl C ws 56% greter with ST compred to CT. There were no differences in soil C in the lower two depths. Overll, soil C sequestrtion ws greter with ST since soil respirtion ws proly lower thn in the CT. There ws significnt interction (P 0.01) etween ll mngement systems nd depth, except CT. Conventionl tillge opertions tend to incorporte plnt mterils, incresing soil C rekdown nd mixing it to lower soil depths creting dilution effect (Tle 1). Totl soil C content incresed significntly with mnure ppliction for oth tillges on the top 2 inches of soil (Tle 1). However, soil C only incresed significntly with mnure ppliction t the 2-4 in depth with CT. This cn e ttriuted to the incorportion of the mnure deeper into the soil profile y the mixing ction of the CT prctices. A similr trend ws oserved t 4-6 in of depth. Soil C content ws not ffected y lndscpe position (P = 0.39). Tle 1. Totl soil C content for conventionl, conventionl with mnure, strip-till, nd strip-till with mnure mngement systems in the reserch site ner Shorter, AL. Totl Soil Cron Conventionl Tillge Strip Tillge No mnure Mnure No mnure Mnure Depth, in % Pr > F Depth Tillge Mnure Tillge x Mnure < <

4 Infiltrtion, in/hr Summit Bckslope Accumultion c c CT CT+M ST ST+M Mngement System Figure 2. Infiltrtion rte s ffected y lndscpe position for conventionl tillge with nd without mnure (CT+M nd CT), nd strip tillge with nd without mnure (ST+M nd ST) in the reserch site ner Shorter, AL. Different letters indicte sttisticl significnce etween lndscpe positions within the sme mngement system. In generl, wter infiltrtion ws incresed y non-inversion tillge prctices in ll lndscpe positions (Fig. 2). Wter infiltrtion ws greter in the summit nd ccumultion positions thn in the ckslope of the ST mngement system. Similrly, infiltrtion ws lowest in the ckslope of the ST+M mngement, ut it wsn t significntly different to the infiltrtion rte of the ccumultion zone. A similr pttern ws oserved with CT+M. This reduced wter infiltrtion rte in the ckslope position cn e ttriuted to lower C ccumultion in the ckslope position. Infiltrtion in the summit nd ckslope for the CT tretment ws greter thn in the ccumultion zone. Wter infiltrtion ws not ffected y mnure ppliction within tillge system. Wter stle soil ggregtes were not ffected y mngement system (P = 0.51) or zone (P = 0.27). This my e due to the lrge vriility in ggregte stility mesurements. CONCLUSION Mnure significntly incresed the soil C content of the topsoil in CT nd ST tretments. Soil C content ws incresed with mnure ppliction deeper in the profile for the CT tretment only. However, mnure ppliction did not pper to improve wter infiltrtion or wter stle ggregtes. Similrly, there were no significnt differences in wter stle soil ggregtes etween tretments or zones. Wter infiltrtion tended to e greter in the summit position for ll the tretments, with the exception of ST. In generl, it seems tht conservtion systems hd greter impct on improving mesured soil qulity prmeters on this lndscpe thn mnure ppliction. REFERENCES Blkcom, K.S., J.A. Terr, J.N. Shw, D.W. Reeves nd R.L. Rper Soil mngement system nd lndscpe position interctions on nutrient distriution in costl plin field. Journl of Soil & Wter Conservtion 60:

5 Nimmo, J.R. nd K.S. Perkings Wet-ggregte stility. In: Methods of Soil Anlysis: Physicl Methods-Prt IV. Eds. J.H. Dne nd G.C. Topp. pp SSSA Pulishing, Mdison, Wisconsin, USA. Hns, J Fctors of soil formtion: A system of quntittive pedology. McGrw Hill Book Compny, New York. Terr, J.A., J.N. Shw, D.W. Reeves, R.L. Rper, E. vn Snten, E.B. Schw nd P.L. Msk Soil mngement nd lndscpe vriility ffects field-scle cotton productivity. Soil Science Society of Americ Journl 70: Terr, J. A., J.N. Shw, D.W. Reeves, R.L. Rper, E. vn Snten nd P.L. Msk Soil cron reltionships with terrin ttriutes, electricl conductivity, nd soil survey in costl plin lndscpe. Soil Science169: