Tillage Effects on Dryland Soil Physical Properties in Northeastern Montana

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1 Iowa State University From the SelectedWorks of Andrew W. Lenssen Tillage Effects on Dryland Soil Physical Properties in Northeastern Montana J. D. Jabro, United States Department of Agriculture Upendra M. Sainju, United States Department of Agriculture Andrew W. Lenssen, United States Department of Agriculture R. G. Evans, United States Department of Agriculture Available at:

2 This article was downloaded by: [Iowa State University] On: February, At: 6: Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 79 Registered office: Mortimer House, 7- Mortimer Street, London WT JH, UK Communications in Soil Science and Plant Analysis Publication details, including instructions for authors and subscription information: Tillage Effects on Dryland Soil Physical Properties in Northeastern Montana J. D. Jabro a, U. M. Sainju a, A. W. Lenssen a & R. G. Evans a a Northern Plains Agricultural Research Laboratory, U.S. Department of Agriculture Agricultural Research Service, Montana, USA Published online: 9 Sep. To cite this article: J. D. Jabro, U. M. Sainju, A. W. Lenssen & R. G. Evans () Tillage Effects on Dryland Soil Physical Properties in Northeastern Montana, Communications in Soil Science and Plant Analysis, :8, 79-87, DOI:.8/6..69 To link to this article: PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the Content ) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at

3 Communications in Soil Science and Plant Analysis, :79 87, ISSN: -6 print / -6 online DOI:.8/6..69 Tillage Effects on Dryland Soil Physical Properties in Northeastern Montana J. D. JABRO, U. M. SAINJU, A. W. LENSSEN, AND R. G. EVANS Northern Plains Agricultural Research Laboratory, U.S. Department of Agriculture Agricultural Research Service, Montana, USA Introduction We evaluated the effect of no tillage (NT) and conventional tillage (CT) on soil penetration resistance (PR), bulk density (BD), gravimetric moisture content (MC), and saturated hydraulic conductivity (Ks) during the fallow phase of a spring wheat fallow rotation. The study was conducted on two soils mapped as Williams loam at the Froid and Sidney sites. Soil measurements were made on 9 May, June, and August at the Froid site and on 6 June and 8 July at the Sidney site. Tillage had no effect on either soil properties except on the PR at Sidney. However, soil PR, MC, and BD varied significantly with depth regardless of tillage and location. Further, soil PR and MC varied with the date of sampling at both locations, and PR generally increased with decreased MC at all soil depths. Soil Ks was slightly influenced by tillage at both locations. Keywords Cover crops, soil structure, soil water Different tillage systems can affect soil physical properties by altering soil conditions and consequently have a direct bearing on crop growth, management, and yield production. The main reasons for tillage in fallow wheat cropping systems are to prepare seedbeds and to control weed growth (Mielke and Wilhelm 998). Tillage-based spring wheat alternating with fallow is a traditional cropping system in the dryland of semi-arid regions of northeastern Montana, where there has been inadequate annual precipitation (< mm) for successive crops. Water is considered a major limiting factor in dryland crop production in semi-arid areas of northeastern Montana. In these low-precipitation areas, fallow is a system component in a -year rotation that has been practiced to build up enough soil moisture content to produce crops on stored water plus precipitation during the growing season (Mielke et al. 98; Mielke and Wilhelm 998). Further, the chemical fallow system is the practice that has been adopted by farmers in recent years to conserve soil water in limited rainfall regions and for weed control to ensure optimum crop production (Mielke et al. 98; Mielke and Wilhelm 998; Schillinger ; Janosky, Young, Received 8 May ; accepted October. This article not subject to U. S. copyright laws. Mention of trade names, proprietary products, or specific equipment is intended for reader information only and constitutes neither a guarantee nor warranty by the USDA-ARS, nor does it imply approval of the product named to the exclusion of other products. Address correspondence to J. D. Jabro, Northern Plains Agricultural Research Laboratory, USDA-ARS, N. Central Avenue Sidney, MT jay.jabro@ars.usda.gov 79

4 8 J. D. Jabro et al. Table Particle-size distribution and textural class for both Williams soils at Froid and Sidney locations in MT Location Depth (cm) a Sand (%) Silt (%) Clay (%) Textural class Froid Sidney 6 Sandy loam 6 7 Sandy loam 9 9 Sandy loam 9 Clay loam 6 Clay loam 7 8 Clay loam a Each measurement was replicated eight times. Table Analysis of variance for penetration resistance (PR), bulk density (BD), and moisture content (MC) taken during the fallow phase of a wheat fallow rotation at Froid and Sidney dryland sites Froid Sidney Source PR BD MC PR BD MC Tillage (T) NS NS NS NS NS Depth (D) T D NS NS NS NS Date (Dt) NS NS T Dt + NS NS D Dt NS NS NS + T D Dt + NS NS NS NS Notes. NS, nonsignificant. + Significant at the. probability level. Significant at the. probability level. Significant at the. probability level. Significant at the. probability level. and Schillinger ). Conventional tillage reduces soil organic matter by increasing its mineralization rate, and soil under this system can be highly vulnerable to wind erosion. No-till fallow has increased because the no-till system conserves soil water, reduces wind erosion and farm energy use, improves soil organic matter, and often increases crop yields compared with conventional tillage (Lenssen, Johnson, and Carlson 7; Sainju et al. 7). Numerous studies report that bulk density in the top to cm of soil differed between tillage and conventional tillage systems (Ehlers et al. 98; Radcliffe et al. 988; Hill 99; Hubbard et al. 99; Wander and Billero 999). However, other studies report that differences in bulk density were not significant between tillage systems (Taboada et al.

5 Tillage Effects on Soil Physical Properties 8 Table Effects of tillage and depth on soil penetration resistance during the fallow phase of a wheat fallow rotation at Froid and Sidney dryland sites PR (MPa) Tillage Depth (cm) Froid Sidney NT CT LSD (.) NS. NT.8a.9a CT.7a.8b Notes. Different letters in each column indicates significant differences at the P. level by the least square means. Table Effects of tillage and depth on soil gravimetric moisture content (MC) during the fallow phase of a wheat fallow rotation at Froid and Sidney dryland sites MC (g g ) Tillage Depth (cm) Froid Sidney NT CT LSD (.) NS. 998; Arshad, Franzluebbers, and Azooz 999; Logsdon, Kasper, and Camberdella 999; Ferreras et al. ). Several studies comparing tilled and untilled soils found greater penetration resistance in untilled soil, especially in the upper cm (Ehlers et al. 98; Radcliffe et al. 988; Hammel 989; Hill 99; Wander and Billero 999; Ferreras et al. ). Little information is available on the effect of tillage on soil physical properties during fallow. Thus, the objective of this study was to evaluate the effect of no-till (NT) chemical fallow and conventional tillage (CT) fallow management on soil penetration resistance (PR), bulk density (ρ b ), gravimetric water content (MC), and saturated hydraulic conductivity (K s ) during fallow in spring wheat fallow rotation under dryland conditions.

6 8 J. D. Jabro et al. Materials and Methods Sites and Soil Description The study was conducted in spring at two locations in eastern Montana, USA, with differing soil texture: the Froid site, located km north of Culbertson, and the Sidney site, located km west of Sidney in eastern Montana, USA. The soil at the Froid site was located in an area mapped as a Williams loam (fine-loamy, mixed, superactive, frigid Typic Argiustolls) formed in glacial till parent material with % slope. The Sidney site was located in an area mapped as Williams loam (fine-loamy, mixed, superactive, frigid Typic Argiustolls) formed in calcareous glacial till parent material with % slope. The experimental design was a randomized complete block with four replications and two treatments. Plots were m wide and m long. The treatments included NT and CT fallow management altering with spring wheat (Triticum aestivum L.). The CT treatment plots were tilled with a sweep plow to a depth of cm prior to spring wheat seeding to prepare a seedbed in the spring and to control the weeds. In NT fallow plots, herbicides, primarily glyphosate [N-(phosphonomethyl) glycine)] and,-d (,-dichlorophenoxyacetic acid), were applied to kill the weed growth (Sainju et al. 7; Jabro et al. 9). Measurement of Soil Physical Properties Soil physical properties, including PR, MC, and Ks, were measured at the Froid and Sidney experimental sites. Soil PR, BD, and MC measurements were made on 9 May, June, and August at the Froid site and on 6 June and 8 July at the Sidney site. Soil PR was measured by pushing a hand-held digital cone-tipped (.8-mm in diameter) penetrometer (Field Scout, SC 9 soil compaction meter; Spectrum Technologies, Inc., Plainfield, Ill.) into the soil at three positions on a transect across each plot, one at the middle of the plot and the other two at each end of the plot. Soil PR readings were recorded in.-cm increments to a depth of cm. Using a soil core sampler, two undisturbed soil cylindrical core samples ( cm long cm in diameter), one at each end of the plot, were collected from each of the plots in -cm increments to a depth of cm. Soil cores were used to measure BD and MC from oven-dried undisturbed soil cores as mass of oven-dried soil per volume of core. Particle-size distribution for each core at each depth was determined using the hydrometer method (Table ). Soil Ks was measured using the constant head well permeameter method (Reynolds and Elrick 98). Soil Ks measurements were made between May and June. Statistical Analysis Statistical analysis of data was conducted using the analysis of variance of repeated measures in the mixed model procedure of SAS software (Littell et al. 996). Means were separated using the least square means test at a significance level of P.. The variables PR and MC were tested for linearity, and a weak linear relationship was found among these two soil parameters. Therefore, the MC was not used as a covariate in the analysis of the data (Jabro et al. 9).

7 Tillage Effects on Soil Physical Properties 8 cm Froid Cover Crop Penetration Resistance, LSD(.) =. NT CT Penetration resistance, PR ( MPa) cm cm May 9 June August Date of sampling Figure. Temporal variations of soil penetration resistance (PR) at depths of,, and cm in sandy loam during the fallow phase of a wheat fallow rotation at the Froid site in MT. Results and Discussion Analysis of variance results for PR, BD, and moisture content at the Froid and Sidney sites are presented in Table. Results showed that no soil properties differed significantly between NT and CT tillage practices, except for soil PR at the Sidney site. The PR was significantly greater in NT than in CT when averaged across three depths at the Sidney site (Table ). The interaction between tillage and soil depth for MC was significant at the Sidney site (Tables and ). The NT was wetter than the CT treatment in the - to -cm depth while in the - to -cm depth the CT treatment was wetter than the NT at both sites. The PR, BD, and MC varied significantly with soil depth at both sites (Tables and ). Soil BD was greater at depths of and cm than at cm deep and increased in August at cm deep but decreased at cm deep in both tillage treatments

8 8 J. D. Jabro et al. cm Penetration Resistance, LSD(.) =.8 NT CT Penetration resistance, PR ( MPa) cm cm June 6 August 8 Date of sampling Figure. Temporal variations of soil penetration resistance (PR) at depths of,, and cm in loam soil during the fallow phase of a wheat fallow rotation at the Sidney site in MT. and sites (results not shown). At Froid, PR increased from May to August regardless of tillage treatment and soil depth (Figure ). The PR was lower in CT than in NT at depths of and cm in June but was greater under CT than under NT at - cm deep in August at the Sidney site (Figure ). Greater soil PR values in August were attributed to lower moisture contents in the soil, due to small amounts of precipitation at the end of the growing season in northeastern Montana (Figure ). Soil MC across NT and CT tillage systems decreased regardless of soil depth at both sites (Figure ). These were associated directly with drought conditions and limited precipitation at the end of the growing season at both sites (Figure ). Soil BD varied significantly among dates of sampling as averaged across NT and CT at the three depths at both locations (Figure ). The BD was significantly increased with soil depth where the lowest BD values were recorded at the soil surface at both locations regardless of the sampling date.

9 Tillage Effects on Soil Physical Properties 8 Sidney Froid Rainfall, mm May Jun Jul Aug Sep Oct Figure. Rainfall distribution during the growing season at Froid and Sidney locations (color figure available online). Moisture content, MC (g g ) Moisture content, MC (g g ) Froid, Cover crop cm cm cm May 9 June August cm cm cm June 6 August 8 LSD(.) =.6 LSD(.) =. Sidney, Cover crop Figure. Temporal variations of soil moisture content (MC) at depths of,, and cm across NT and CT tillage systems at Froid and Sidney locations. The analysis of variance showed no significant differences in soil Ks between NT and CT tillage treatments. Soil Ks was slightly influenced by tillage and varied between tillage treatments at both locations (Figure 6). Because there was significant spatial variation in soil Ks measurements within each tillage treatment, differences between tillage treatments were not statistically significant (Figure 6). The coefficients of variation of soil Ks measurements for Froid and Sidney sites were 6% and %, respectively.

10 86 J. D. Jabro et al. Bulk density, BD ( Mg m ) Bulk density, BD ( Mg m ) Froid, Cover crop cm cm cm May 9 June August Sidney, Cover crop LSD(.) =. June 6 August 8 LSD(.) =. cm cm cm Figure. Temporal variations of soil bulk density (BD) at depths of,, and cm across NT and CT tillage systems at Froid and Sidney locations. Ks (cm h ) 6 Cover crop Study CT NT Froid Sidney Figure 6. Saturated hydraulic conductivity for fallow tillage methods for measured at cm deep for loam and sandy loam soils at Froid and Sidney sites, respectively. Conclusions Results indicated that tillage had no effect on soil properties except on the PR at the Sidney site. However, soil PR, MC, and BD varied significantly with depth regardless of tillage and location. Further, soil PR and MC varied with the date of sampling at both locations, and PR generally increased with decreased MC in soil at all depths. Soil Ks was slightly influenced by tillage at both sites.

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