effects of tillage systems and landscape on soil

Soil & Tillage Research, 25 (1992) 43-52 43 Elsevier Science Publishers B.V., Amsterdam

Effects of tillage systems and landscape on soil

B.R. Khakural, G.D. Lemme, T.E. Schumacher and M.J. Lindstrom South Dakota State University Agricultural Experiment Station, Brookings, SD 57007, USA

(Accepted 4 March 1992 )

ABSTRACT

Khakural, B.R., Lemme, G.D., Schumacher, T.E. and Lindstrom, M.J., 1992. Effects of tillage systems and landscape on soil. Soil Tillage Res., 25: 43-52.

The rolling nature of much of the glaciated western cornbelt results in poorly- and well-drained soils being managed in a similar manner. The effects of four tillage systems (moldboard plow, chisel plow, ridge-till and no-till) and two cropping systems (continuous corn and corn/soybean rotation) on soil properties was studied across well drained Beadle (fine-loamy, montmorillonitic, mesic Typic Ar- giustoll) and poorly drained Worthing (fine, montmorillonitic, mesic Typic Argiaquoll) soils. Wor- thing surface soil had a lower hydraulic conductivity, higher volumetric moisture, pH, and available P and K than the Beadle soil. Ridge-till and no-till treatments resulted in higher surface volumetric water and bulk density, and lower soil temperature than the moldboard plow plots in the Beadle soil. Saturated hydraulic conductivity increased over time for the ridge-till and no-till treatments on the Beadle soil. Water use (evapotranspiration) was similar among tillage treatments in either soil. Sur- face aggregate stability was influenced only within the corn/soybean rotation, in which stability was higher in no-till than the moldboard or chisel plow treatments in the Beadle soil. Few differences in chemical properties attributable to tillage systems were found in these soils. High residue tillage systems resulted in greater differences in soil properties on the well-drained member of the soil catena. The beneficial effects of the soil property changes on the well-drained Beadle soil appear to outweigh the effects of high residue tillage on the Worthing soil.

INTRODUCTION

Conservation tillage systems leave most of the previous crop's residue on the soil surface by minimizing mechanical manipulation and mixing of the soil. The minimal mixing of the soil, combined with crop residue on the surface, results in changes in soil physical and chemical properties over a period of time (Blevins et al., 1983; Griffith et al., 1988 ). The extent, type, and tim-

Correspondence to: G.D. Lemme, West Central Experiment Station, PO Box 471, Morris, MN 56267, USA. *This article is a joint contribution from South Dakota State University Agricultural Experi- ment Station and USDA-Agricultural Research Service, Journal No. 2579.

© 1992 Elsevier Science Publishers B.V. All rights reserved 0167-1987/92/$05.00

44 B.R. KHAKURAL ET AL.

ing of changes in soil properties are likely to depend on soil series and landscape position. Soil catenas in the western cornbelt contain both poorly and well-drained soils. A change from intensive to conservation tillage systems is likely to result in differences in the type and time scale of changes in soil properties within these soil catenas.

Research results on the effect of conservation tillage systems (particularly no-tillage) on soil porosity and related properties have not been consistent. No-till has been reported to increase surface bulk density and decrease hydraulic conductivity (K-sat) and infiltration rate compared with conventional tillage systems (Gantzer and Blake, 1978; Lindstrom et al., 1984). However, other studies have shown no change in bulk density (Blevins et al., 1983) whereas increased K-sat and infiltration rates have been reported in some soils (Blevins et al., 1983). Several authors have attributed the increased infiltration rate in no-till system to increased earthworm activity and voids left by decomposing roots (Gantzer and Blake, 1978). There are several reasons for the differences in effects of conservation tillage on soil properties reported in the literature, including differences in climate, timing of measurements, and differences in soil properties resulting from differences in the soil forming process (Benoit and Lindstrom, 1987 ).

Soil water conservation is one of the major advantages of reduced tillage systems. Numerous studies have reported greater surface volumetric water content under conservation tillage practices than under conventional tillage (Blevins et al., 1983; Johnson et al., 1984; Mielke et al., 1986).

Surface residue cover, which reduces evaporation of soil moisture in conservation tillage systems, also reduces surface soil temperature. In-row soil temperature at a depth of 0.5 m was highest in conventional tillage and lowest in no-till system in Wisconsin (Johnson and Lowery, 1985). Reduced soil temperature in no-till systems could affect crop development adversely in all northern climate soils but especially in wet soils that are slower to warm up than well-drained soils (AI-Darby and Lowery, 1987 ).

Differences in organic matter, N, P distribution and content, and K distribution were attributed to tillage treatments (Shear and Moschler, 1969; Blev- ins et al., 1983 ). Organic matter, organic N, available P and K tended to con- centrate at the surface in no-till treatments. Rapid acidification of the soil surface has been observed under no-till systems (Blevins et al., 1983 ).

The results of many long term tillage studies indicate that a selective rela- tionship exists between soil drainage and tillage system. All conservation tillage systems performed as good as or better than moldboard plow systems on well-drained soils (Griffith et al., 1973; Dick and Van Doren, 1985 ). How- ever, no-till corn yields, especially in continuous corn rotations, were reduced substantially on poorly drained soils (Dick and Van Doren, 1985; Griffith et al., 1988). No-till corn yields on low organic matter, poorly drained soils,

EFFECTS OF TILLAGE SYSTEMS AND LANDSCAPE ON SOIL 4 5

improved as soil structure improved after 3 years of no-till. Some authors suggest that ridge-till planting could be a viable alternative on poorly drained soils (Radke, 1982; Griffith et al., 1988).

The glacial morainic landscape of eastern South Dakota consists of mod- erately rolling hills with many closed undrained depressions. Well drained, somewhat poorly drained and poorly drained soils are commonly located on the same farm and frequently in the same field. These soils are managed similarly because of their close proximity. Farmers working with these soil catenas need to be aware of the effects of different tillage systems and crop rotations on soil properties when selecting a farming system.

This study differs from other soil by tillage interaction studies, in that both the well and poorly drained soils studied are located within the same landscape and in the same field, in that Eastern South Dakota receives less precipitation than central and eastern cornbelt states where most of the earlier studies were conducted, and in that, in general, poorly drained soils in the western cornbelt are not drained artificially, as is common in the eastern cornbelt.

This study investigated the interaction of tillage systems and soil drainage class (well and poorly drained soils found within a soil catena) on soil physical and chemical properties under continuous corn and corn/soybean rotations.

MATERIALS AND METHODS

The study was conducted at the Eastern South Dakota Soil and Water Re- search Farm near Madison, SD. The soils used in this study were a well drained Beadle (fine-loamy, montmorillonitic, mesic Typic Argiustoll) and a poorly drained Worthing (fine, montmorillonitic, mesic Typic Argiaquoll). The Beadle and Worthing soils represent a catena, with the Beadle soil extending from the summit through the backslope and the Worthing soil in the toeslope position.

Tillage plots were established I year prior to commencing the study. Tillage and cropping sequence treatments were arranged in a split plot design (tillage as main plot and cropping sequence as subplots) with three replications on each soil. Tillage treatments were moldboard plow (MB), chisel plow (CP), ridge-till (RT) and no-till (NT). Moldboard plow plots were plowed in the fall and worked with a field cultivator in the spring. Chisel plow plots were worked in the fall and tandem disked in the spring. Planting was done directly on ridges without primary tillage in RT plots. Ridges were reshaped every summer during the cultivation operation. No-till plots were planted and maintained without cultivation.

A starter fertilizer ( 13% N, 33% P, 13% K) was applied at planting at the rate of 15 kg N ha- 1. Additional N ( 120 kg ha - 1 ) was applied in a band in the third week of June. Ammonium nitrate and urea were applied as N sources


during Years 1 and 2 respectively. All tillage treatments except NT were cul- t ivated once after fertilizer application.

Continuous corn and corn/soybean rotations were studied. Bulk density, K-sat, soil moisture and soil temperature measurements were obtained only from continuous corn plots. Bulk density values reported are the mean of eight observations, K-sat values are the mean of four observations, and soil moisture data are the mean of 26 measurements. Temperature values reported are the mean of 126 observations (Table 1 ). Measurements taken during 1986 (Year 2) and 1987 (Year 3) are reported here.

Composite soil samples from each experimental unit were collected from the in-row area at 0-0.15 m and 0.15-0.6 m depths in the fall for soil fertility tests. Undisturbed surface core samples were taken from the row area for bulk density and K-sat measurements by the use of a Uhland sampler.

Soil water content was moni tored with a neutron probe throughout the growing season at 2-week intervals. Soil water content measurements were taken after each rainfall event. Daily max imum and min imum soil temperatures were recorded at a depth of 0.1 m with a dial stem thermometer during the early growth period ( 8 weeks). Climatic data, including precipitation, air temperature, wind run, and pan evaporation, were collected at the site. Sea- sonal evapotranspiration (ET) was obtained from a water balance equation: E T = R +_ W where R is the rainfall and W is the measured change in profile soil water content. Runoff and drainage water were assumed negligible and were excluded from this calculation.

TABLE 1

Effect of tillage system on surface physical properties of Beadle and Worthing soils

Tillage Bd K-sat ( m m h - ~ ) 0v Temperature ET system (Mg m -3) ( m 3 m -3) ( ° C ) ( m m )

Year 2 Year 3

Beadle soil MB 1. la 107 b 37 a 0.31 a 21.2 c 347 CP 1.1 ~ 122 b 53 a 0.33 ~b 20.8 bc 347 RT 1.2 b 20 ~ 76 b 0.36 ~: 20.0 ~ 358 NT 1.2 b 42 a 73 b 0.37 c 20.2 ~b 394

Worthing Soil MB 1. I a 2 43 b 0.47 20.5 357 CP 1.1 a 3 11 ab 0.49 21.0 354 RT 1.2 b 1 15 ab 0.47 20.7 333 NT 1.2 b 14 8 a 0.48 21.0 333

Bd = bulk density; K-sat = hydraulic conductivity; MB = moldboard plow; CP = chisel plow; RT = ridge- till; N T = no-till; 0v = volumetric water content; ET = seasonal evapotranspiration. Significant differences within a soil series and year are marked with a different superscript ( P < 0.05 ).

EFFECTS OF TILLAGE SYSTEMS AND LANDSCAPE ON SOIL 47

A constant head method was used to measure K-sat (Klute and Dirksen, 1986). Aggregate stability of pre-humidified air dried samples were determined using the method of Kemper and Rosenau (1986). Standard proce- dures were used to determine readily oxidizable organic matter, available P, K and nitrates (South Dakota State University, 1987). A 1 : 1 soil to water suspension was used for pH measurements. Soil nitrates were determined for both the 0-0.15 and 0.15-0.6 m depths.

An analysis of variance (ANOVA) a general linear model program was used to test the significance of differences among treatments. The least square means (LSM) were used to make mean comparisons between treatments if an overall significant F was found.

RESULTS AND DISCUSSION

There were no tillage treatment by year interactions for soil properties except for saturated hydraulic conductivity. Soil property values are given as 2- year means except for K-sat and aggregate stability.

Bulk density and hydraulic conductivity

Ridge-till and NT plots had higher surface bulk density than MB and CP systems in both Beadle and Worthing soils (Table 1). However, the surface bulk densities were not high enough to substantially limit root growth. Mold- board and CP Beadle plots in Year 2 had higher K-sat values than RT and NT plots (Table 1 ). However, exactly opposite results were obtained in Year 3. The increase in K-sat values of RT and NT systems in Year 3 compared with Year 2 in the Beadle soil may be caused by the formation of more continuous, preserved root channels in Year 3 because of the lack of disturbance in the row area of these systems. More root channels were observed visually in the Beadle soil under NT and RT systems than under MB and CP systems when the cores used for K-sat measurement were inspected in Year 3. The contribution of root channels in the formation of surface soil macro-pores and increased hydraulic conductivity was reported for similar soils in Minnesota (Gantzer and Blake, 1978 ).

Saturated hydraulic conductivity values were not different among tillage systems in the Worthing soil in Year 2. The MB plots had higher K-sat values than the NT plots in the Worthing soil in Year 3. The increase in K-sat values in the Worthing soil in Year 3 under MB might be because of the tillage-induced cloddy surface of the MB plots in the Worthing soil. Moldboard plow- ing and secondary tillage on the Worthing soil occurred under supra-optimal conditions because of a wet fall and spring. This resulted in a stable cloddy structure and a poor seedbed.

48

Soil water content

B.R. KHAKURAL ET AL.

No-till and RT plots had higher mean volumetric water contents in the Ap horizon than the MB plots of the Beadle soil (Table 1 ). Surface water content was related inversely to tillage intensity and related directly to surface residue cover (Table 2). This result is in agreement with most previous tillage research (Gantzer and Blake, 1978; Blevins et al., 1983; Mielke et al., 1986). Higher residue cover in the conservation tillage systems may have reduced evaporation from the soil surface and increased soil moisture content (Blev- ins et al., 1983).

No differences in 2-year seasonal mean surface soil water contents were detected as a result of differences in tillage systems in the poorly drained Wor- thing soil (Table 1 ). The Worthing soil was near saturation on all treatments during most of the growing season in Year 2. Capillary action from the high water table present in this soil may have negated any tillage-induced differences in evaporation (Table 1 ). The water table in the Worthing soil is esti- mated to be between 0.9 m and 0.3 m from the surface in early spring and summer (National Cooperative Soil Survey, 1979). The MB plots had con- sistently lower surface soil water contents compared with the other tillage treatments in Year 3 (Fig. 1 ). The lower water content of the Ap horizon of

TABLE2

Tillage and crop rotation effects on surface residue cover and aggregate (0.1-0.2 m m ) stability of Beadle and Worthing soils

Tillage Residue Cover (%) Stable Aggregates (%) system

Year 2 Year 3 Year 2 Year 3

cc c/s cc c/s cc c/s cc c/s

Beadle Soil MB 8 ~ 3 a 15 ~ 5 a 88 82 a 95 94 ~b CP 41 b 22 b 56 b 16 ~ 89 85 ~b 93 92 a RT 35 b~ 23 b 65 b 50 b 83 86 ~b 93 94 ~b NT 53 c 37 c 81 c 51 b 85 88 b 95 95 b

Worthing Soil MB 6 a 3 a 6 a 4 a 93 91 94 b 95 c CP 35 b 15 b 23 b 10 ab 91 92 90 a 92 b RT 50 c 23 b 25 ~ 20 ~ 92 89 88 a 86 ~ NT 48 c 20 b 36 c 31 c 91 90 92 ab 92 b

M B = m o l d b o a r d plow; CP=ch i se l plow; RT=ridge-ti l l ; NT=no- t i l l ; C C = c o n t i n u o u s corn; C / S = corn/soybeans . Significant differences within a soil series, cropping sequence and year, are marked with a different superscript ( P < 0.05 ).


1 O0 -

9 0 -

E ao- E

a 7oi o

o 60

5 0 "

4 0

MB

2'0 4b 6b s'0 1 ~o Doys after plonting

CP

RT

NT

120

Fig. 1. Tillage effects on water storage in the Ap horizon (0-0.18 m) of Worthing soils in Year 2.

the Worthing soil in Year 3 was related to the stable clods formed in seedbed preparation.

No difference in total seasonal water use (evapotranspiration) was observed among the tillage treatments in either soil (Table 2 ). Olson and Schoe- berl (1970), similarly, did not find differences in water use among tillage systems on Beadle and poorly drained Whitewood (fine-silty, mixed, mesic Cumulic Haplaquolls) soils located on the same farm.

Soil temperature

Mean daily soil temperature over the first 8 weeks of the growing season at a depth of 0.1 m was higher in the MB treatment than in the RT and NT treatments on the Beadle soil (Table 1 ). The lower soil temperatures in the reduced tillage systems are related to increased residue cover found in RT and NT treatments (Table 3). Surface residues reflect incoming radiation and reduce soil temperature (Van Wijk et al., 1959). There was no difference in mean daily soil temperature among tillage systems on the Worthing soil.

Soil aggregate stability

The surface aggregate stabilities of both soils were high throughout the study (Table 2 ). The tillage effect was most pronounced in the corn/soybean rotation. Under the corn/soybean rotation, NT treatment on Beadle soil had greater aggregate stability than MB and CP treatments in Years 2 and 3, re-


TABLE 3

Tillage effects on chemica l proper t ies o f Beadle and Wor th ing Soils (averaged over years)

Tillage Surface Deep sys tem

p H O M EC P K N O j- N O j" ( g k g - l ) ( m S c m -1 ) ( m g k g -1 ) ( m g k g - l ) ( m g k g - l ) ( m g k g - I )

Beadle Soil MB 7.1 b 38.8 5 12.2 246 8.7 4.8 CP 7.7 b 39.8 6 8.8 259 8.4 4.7 RT 6.5 ~ 41.5 5 14.7 260 10.3 4.4 N T 6,8 a 44.6 5 16.6 319 8.2 3.6

Worthing Soil MB 7.6 43.6 41 ab 29.5 a 438 11.4 ab 4.3 a CP 7,6 40.9 39 a 37.5 ~b 420 8.6 a 3.8 ~ RT 7,5 43.8 49 b 38.9 -b 368 15.1 b 7.1 b N T 7.6 40.5 36 a 41.7 b 368 7.6 ~ 4.1 ~

O M = organic matter ; EC = electrical conductivity; MB = moldboard plow; CP = chisel plow; RT = ridge- till; N T = no-till; Surface = 0 .0 -0 .15 m; Deep = 0 .15-0 .6 m, Significant differences wi th in a soil series are m a r k e d with a different superscr ip t ( P < 0.05) .

spectively. The lower aggregate stability values of MB and CP treatments compared with NT under the corn/soybean rotation might be related to lower residue cover left by these treatments (Table 2 ). Surface mulch protects soil aggregates from disintegration by the sheering forces of falling rain drops. Differences in aggregate stability on the Worthing soil were only observed in Year 3. The higher aggregate stability of the MB treatment compared with other tillage treatments in the Worthing soil may be related to the cloddy surface discussed earlier.

Soil chemical properties

Crop rotations did not significantly affect soil chemical properties during the period of this study. Ridge-till and NT systems on the Beadle soil had lower surface pH than did the MB and CP treatments (Table 3 ). There was no difference in surface pH between RT and NT treatments. However, the surface of MB plots were less alkaline than CP plots, because of the incorpo- ration of calcareous subsoil into the surface layer by the chisel plow. Acidifi- cation of the soil surface under RT and NT systems is probably because there was less mixing of surface applied fertilizers (Blevins et al., 1983 ). Continu- ous surface application of ammonium nitrogen fertilizers can acidify the top- soil. Acidification of the soil surface under NT or RT systems could be beneficial in strongly alkaline soils, which are common in sub-humid regions of the corn belt.


There was no difference in surface pH values of the Worthing soil with tillage treatment. The presence of free carbonates in the surface soil resulted in a highly buffered system that could mask the acidification process seen with the reduced tillage systems in the Beadle soil.

No difference in available P was observed with tillage system in the Beadle soil (Table 3 ). The Worthing NT plots had higher P levels than the MB plots. Potassium levels were not affected by tillage system in either soil.

No difference in surface organic matter was observed with tillage system (Table 3 ). Neither surface (0-0.15 m ) nor subsoil (0.15-0.6 m ) nitrate levels were significantly different among tillage treatments in the Beadle soil. Ridge-till Worthing plots contained higher levels of nitrate than the NT and CP treatments. Deep nitrate levels (0.15-0.6 m) were higher in the RT system than in the MB system. The ridges in the poorly drained Worthing soil might have been better aerated than the fiat seed beds associated with the other tillage systems, resulting in more mineralization and less denitrification.

C O N C L U S I O N S

Poorly drained and well-drained soils that are found within a catena in the western cornbelt did not react to tillage and crop rotation in the same manner. This study indicates that some changes in soil properties occurred, as a result of the tillage system used in a relatively short period of time (3 years) in the well-drained member of this soil catena. Surface water content throughout the growing season was greatest under the no-tillage corn/soybean system. Soil water is generally the most limiting factor for crop production in this region. The higher water content is probably the result of the combined effects of higher surface residue cover, increased hydraulic conductivity, and generally more stable aggregates than those observed in the more intensively tilled moldboard and chisel plow systems. Fewer differences were observed with tillage system in the poorly drained soil.

Although the two soils respond differently to tillage, they are likely to be managed alike because of their close proximity. The positive effects of the high residue systems on the properties of the Beadle soil were greater than the negative influence found on the poorly drained soils in this study. Even though tillage system had little effect on most soil properties of the Worthing soil, the cloddy seedbed produced in Year 3 by the moldboard plow had a negative effect on stand development (Khakural, 1988). Tillage systems with mini- mum surface disturbance can reduce this problem, which is associated with wet years and poorly drained soils. Yield measurements taken on these plots confirmed the overall advantage of the high residue tillage systems in this soil catena (Khakural, 1988).


REFERENCES

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effects of tillage systems and landscape on soil

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