Impacts of tillage and no-till on production of maize and soybean on an eroded Illinois silt loam soil

Soil & Tillage Research 52 (1999) 37±49

Impacts of tillage and no-till on production of maize and soybean on an eroded Illinois silt loam soil I. Hussaina, K.R. Olsonb,*, S. A. Ebelharc b

a Mohalla Hariwalla, Pindi Gheb, Dist Attock, Pakistan Department of Natural Resources and Environmental Sciences, W-401C Turner Hall, University of Illinois, 1102 S. Goodwin Ave., Urbana, IL 61801, USA c Dixon Springs Agricultural Center, Simpson, IL, USA

Received 25 May 1998; received in revised form 10 November 1998; accepted 17 May 1999

Abstract In the United States, millions of hectares of highly erodible cropland have been in the Conservation Reserve Program (CRP) for the past 10 years. Any conversion of CRP land back to maize (Zea mays L.) and soybean (Glycine max L. Merr.) production could require the use of conservation tillage systems, such as NT and CP, to meet federal and state soil erosion control standards. Evaluations of yield response of these conservation tillage systems such as NT and CP, over time are needed to assess the return of this land to crop production. An eight-year study was conducted in southern Illinois on land similar to that being removed from CRP to evaluate the effects of conservation tillage systems on maize and soybean yields and for the maintenance and restoration of soil productivity of previously eroded soils. Soils had been in tall fescue (Festuca arundinacea L.) sod for more than 10 years prior to the study. In 1989, no-till (NT), chisel plow (CP), and moldboard plow (MP) treatments were replicated six times in a Latin Square Design on sloping, moderately well-drained, moderately eroded phase of a Grantsburg soil (Albic Luvisol) (®ne-silty, mixed, mesic Typic Fragiudalf). Starting with maize, maize and soybean were grown in alternate years. Surface crop residue levels were higher with the NT system than with the CP and MP systems. Soil temperature at 20 cm was lower (1.18C) with NT than with the other systems in 1996. Plant-available water was slightly higher with NT and CP systems than with the MP system. In 1995, maize was taller with the NT system than with the MP and CP systems. The MP system plots had higher plant populations in 1995 and 1996, but crop yields were higher with the NT system than with the MP system. The four-year average maize yields were equal (9.81, 9.74, and 9.80 Mg haÿ1) for NT, CP, and MP systems, respectively, as a result of a signi®cantly higher yield with the MP system in the ®rst year which offset the higher yields with the NT and the CP systems during the last two years. The four-year average soybean yield with NT (2.90 Mg haÿ1) was 15% higher than with the MP (2.55 Mg haÿ1) system. Crop yields for eight years (four years maize and four years soybean) appear to show improved long-term productivity of NT compared with that of MP and CP systems. # 1999 Elsevier Science B.V. All rights reserved. Keywords: Conservation tillage; Yield; Crop growth; Soil water; Plant population

*Corresponding author: Tel.: +1-217-333-9639; fax: +1-217-244-3219 E-mail address: [email protected] (K.R. Olson) 0167-1987/99/$ ± see front matter # 1999 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 7 - 1 9 8 7 ( 9 9 ) 0 0 0 5 4 - 9

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I. Hussain et al. / Soil & Tillage Research 52 (1999) 37±49

1. Introduction In the United States, the Food Security Act of 1985, the 1900 and 1995 Farm bills, and the Illinois T by 2000 Program have resulted in millions of hectares of erodible land previously in row crops being put into the Conservation Reserve Program (CRP) for 10 years. Any conversion of CRP land back to maize and soybean production could require the use of conservation tillage systems, such as NT and CP, to meet soil erosion control standards. Evaluations of yield response of these conservation tillage systems over time are needed to assess returning this land to crop production. The severity of erosion can be reduced by maintaining crop residue on the soil surface (Dickey et al., 1985; Alberts and Neibling, 1994). At planting, with chisel plowing residue cover is 30% and much higher with no-till due to a lack of, or minimum, soil disturbance (Lal et al., 1994). Lueschen et al. (1991), for a maize±soybean rotation in Minnesota, observed 69±82%, 49%, and 10% of soybean residue cover on the soil surface after maize planting in no-tillage, chisel plow, and moldboard plow system plots, respectively. A higher surface residue cover in combination with minimum soil disturbance, affect soil water conservation and soil temperature. The amount of plant-available water in soil at planting time increased and the soil temperature decreased with the amount of plant residue on the soil surface at Lincoln, Nebraska (Wilhelm et al., 1986). From the 1954±1988 data from central Iowa, plantavailable soil water and heat stress during July (summer) were identi®ed by Carlson (1990) as two major weather factors that affected the maize yield. At Sydney, MT, Aase and Tanaka (1987) found that residue on the soil surface reduced the early evaporation during summer from the upper 10 cm of soil compared with that of bare soil, but total soil-water losses during the season were not signi®cantly different. Schillinger and Bolton (1993) compared no-till, stubble mulch, and moldboard plow and found that the residue in no-till decreased the evaporation during frequent rainfall periods, but the evaporation in notill was faster during the dry period of summer due to non-disturbed capillary ¯ow. In Garden City, Kansas, Norwood (1994) studied different crop rotations with

no-till and conventional tillage and found an additional 62% of water below the 0.9-m depth in no-till due to less evaporation and no surface runoff compared with that of conventional tillage. Generally, conservation tillage resulted in an increase in crop yield compared with that of a moldboard plow system. Lawrence et al. (1994) showed in a four-year study in a semi-arid environment in Australia that no-till had a higher crop yield than did reduced till fallow or conventional till fallow. A positive linear response between yields of maize and soybean, and the amount of residue applied to a no-till system was observed by Wilhelm et al. (1986). Lueschen et al. (1991), in a maize±soybean rotation in Minnesota, found an increase of 6.30 Mg haÿ1 in yield of the NT system above the MP system in a dry year. Kapusta et al. (1996) studied the effects of tillage systems for 20 years and found equal maize yield in no-till, reduced till, and conventional tillage despite the lower plant population in notill. Crop rotation in combination with different tillage systems can also affect crop yields. After 12 years of study, a maize±soybean rotation yielded 8.7 Mg haÿ1, compared with 7.7 Mg haÿ1, for continuous maize, while soybean yields were 2.6 Mg haÿ1 in both rotations (Karlen et al., 1991). West et al. (1996) studied the effect of moldboard plow, ridge, chisel and no-till for 20 years in north-central Indiana under different rotations of continuous maize, continuous soybean, maize after soybean, and soybean after maize. No-till maize yield and plant population were reduced 14% and 8%, respectively, in continuous maize. Kapusta et al. (1996) reported greater plant height in no-till compared with that of moldboard plow, while the maize population was lower in no-till in comparison with moldboard plow. Dickey et al. (1994) in Nebraska, studied plow, chisel, disk, and no-till systems on a silty clay loam soil for eight years and found the highest yield for sorghum (Sorghum biocolor (L.) Moench) and soybean under the no-till system. The crop yields with different tillage systems vary from year to year due to the ¯uctuations in weather. No-till corn yielded more in drier than normal years, whereas maize yields with moldboard plow were higher in the wetter than normal years in the moderately well-drained soils of Ohio (Eckert, 1984). No-till maize yields are lower in the early years which could

I. Hussain et al. / Soil & Tillage Research 52 (1999) 37±49

39

be due to lower soil organic carbon and nitrogen mineralization and higher immobilization of fertilizer nitrogen, than those of conventional tillage (House et al., 1984; Rice and Smith, 1984). Rice et al. (1986) and Kapusta et al. (1996) also reported no differences in maize yield with no-till and conventional tillage over time. In different tillage systems, crop yields were also affected by soil drainage conditions. Some researchers reported lower yields with no-till, than conventional tillage in poorly drained soils (Dick and Van Doren, 1985) and higher yields for well drained soils (Wagger and Denton, 1992; Ismail et al., 1994). Since limited data were available on the long-term tillage responses on sloping and eroded soils in southern Illinois, this project was started in 1989. Tillage effects were not profound in the early years of the study (Kitur et al., 1994). The study was continued with the objective of evaluating long-term tillage systems (no-till, chisel plow, and moldboard plow) effects on maize and soybean yields and the maintenance and restoration of soil productivity of previously eroded soils in southern Illinois.

design was a Youden Type III Incomplete Latin Square (Cochran and Cox, 1957) that allowed for randomization of the tillage treatments (NT, CP, and MP), both by row (block) and by column. This replication was used to control random variability in both directions. Each treatment was randomized six times in 18 plots with a size of 9 m  12 m. The columns were separated with 6 m buffer strips of sod.

2. Methods and materials

Six soil samples from each treatment for gravimetric water contents were taken at planting, 25 days after planting, and at midseason with a 5-cm diameter Oak®eld tube Sampler 1 to a depth of 75 cm. Three soil clods taken from the surface layer at 25 days after planting during both the growing seasons were wetted to ÿ33 kPa water potential and used for clod bulk density (Olson, 1979). Plant-available soil water was determined by subtracting the ÿ1500 kPa water potential content from the gravimetric water content and multiplying by soil bulk density at ÿ33 kPa water potential (Nizeyimana and Olson, 1988). Daytime soil temperature measurements (six per treatment) were made between 8:00 and 17:00 h at 10-cm depth with portable soil thermometers at 25 days after planting. The percentage surface residue was determined after planting by the line-transect method (Hill et al., 1989). Plant population for the central 0.001 ha of each plot was determined by counting and all plant heights in the central 0.001 ha of each plot were measured at 25 days after planting. Leaves from maize and soybean were dried at 708C and analyzed by A&L Laboratories to determine the chemical content (A&L Laboratory

A tillage experiment was started on April 12, 1989, at the Dixon Springs Agricultural Research Center in southern Illinois. The soil at the study site was a moderately eroded phase of Grantsburg silt loam (Albic Luvisol) (Dudal, 1970) (®ne-silty, mixed, mesic Typic Fragiudalf) (Soil Survey Staff, 1975) with an average depth of 64 cm to a root-restricting fragipan. Grantsburg soil was formed in loess under forest vegetation and underlain at a depth of 2±5 m by siltstone. The area, with an average slope of 6%, had been in tall fescue hayland for >10 years prior to the start of this experiment. On April 12, 1989, lime (CaCO3) with 94% calcium carbonate equivalent, at the rate of 3.1, 4.9, and 7.3 Mg haÿ1, was applied on upper, middle, and lower rows of the plot area, respectively, to raise the soil pH of each row to the optimum level for maize and soybean production. Three tillage treatments, namely no-till (NT), chisel plow (CP), and moldboard plow (MP), were established on April 27, 1989. Starting with maize in 1989, maize and soybean were grown in alternate years. The experimental

2.1. Field activities and tillage operations The implements used in each tillage system and depth of tillage were as follows: NT (no-tillage), CP (chisel plowed to 15 cm with diskings to 5 cm), and MP (moldboard plowed to 15 cm with diskings to 5 cm). The actual type, date, and number of primary and secondary tillage operations applied to the plot area are listed in Table 1. The cultural practices used including crop, year, planting date, seeding rate, and fertilizer application rates are provided in Table 2. The weed control including the herbicide, rate and date of application are listed in Table 3. 2.2. Field measurements and sampling

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I. Hussain et al. / Soil & Tillage Research 52 (1999) 37±49

Table 1 Type, date and number of field operations on plot area at Dixon Springs, IL Year

System

No-till

Chisel

Moldboard

date

No.

date

No.

date

No.

1989

plowing disking disking

Ð Ð Ð

Ð Ð Ð

27 Apr 27 Apr 12 May

1 2 1

27 Apr 27 Apr 12 May

1 2 1

1990

plowing disking disking

Ð Ð Ð

Ð Ð Ð

05 Jun 05 Jun 06 Jun

1 1 1

05 Jun 05 Jun 06 Jun

1 1 1

1991

plowing disking disking

Ð Ð Ð

Ð Ð Ð

03 May 07 May 08 May

1 2 1

03 May 07 May 08 May

1 2 1

1992

plowing disking disking

Ð Ð Ð

Ð Ð Ð

26 May 26 May 27 May

1 1 1

26 May 26 May 27 May

1 1 1

1993

plowing disking disking

Ð Ð Ð

Ð Ð Ð

10 May 16 May 17 May

1 2 1

10 May 16 May 17 May

1 2 1

1994

plowing disking disking

Ð Ð Ð

Ð Ð Ð

31 May 31 May 08 Jun

1 1 1

31 May 31 May 08 Jun

1 1 1

1995

plowing disking disking

Ð Ð

Ð Ð

06 Apr 30 May 31 May

1 2 1

06 Apr 30 May 31 May

1 2 1

1996

plowing disking disking

Ð Ð Ð

Ð Ð Ð

05 Jun 05 Jun 05 Jun

1 1 1

05 Jun 05 Jun 05 Jun

1 1 1

Table 2 Crop, planting date, seeding rate and fertilizer rates used in the present study Year

Crop

Planting date

Seeding rate (seeds haÿ1)

N (kg haÿ1)

P (kg haÿ1)

K (kg haÿ1)

1989 1990 1991 1992 1993 1994 1995 1996

maize soybean maize soybean maize soybean maize soybean

12 07 08 22 17 08 31 05

64 000 432 000 64 000 432 000 64 000 432 000 64 000 432 000

212 0 168 0 184 0 218 0

67 67 67 0 55 0 55 0

116 260 260 0 232 0 232 0

May Jun May May May Jun May Jun

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41

Table 3 Weed control practices used during the study Year

Herbicide

Rate

Date ÿ1

1989

Glyphosate Atrazine Metolachlor

2.34 l ha 3.4 l haÿ1 2.3 l haÿ1

21 Apr 12 May 12 May

1990

Glyphosate Metolachlor Sethoxydim Metrubuzin and Chlorimuron Surfactant

2.34 l haÿ1 2.34 l haÿ1 1.90 l haÿ1 0.50 kg haÿ1 0.62 l 100 lÿ1

01 08 08 08 08

1991

Gramoxone Metolachlor Atrazine

2.34 l haÿ1 2.34 l haÿ1 4.68 l haÿ1

08 May 08 May 08 May

1992

Metolachlor Sethoxydim Metrubuzin and Chlorimuron Surfactant

2.34 l haÿ1 1.90 l haÿ1 0.50 kg haÿ1 0.62 l 100 lÿ1

22 22 22 22

1993

Atrazine Metolachlor Glyphosate

3.5 l haÿ1 2.3 l haÿ1 2.33 l haÿ1

17 May 17 May 17 May

1994

Glyphosate Metolachlor Metrubuzin and Chlorimuron Surfactant

2.33 l haÿ1 2.33 l haÿ1 0.42 l haÿ1 0.48 kg haÿ1

08 08 08 08

1995

Glyphosate Alachlor Atrazine

2.33 l haÿ1 2.34 l haÿ1 4.68 l haÿ1

31 May 31 May 31 May

1996

Glyphosate Glyphosate

2.33 l haÿ1 2.33 l haÿ1

05 Jun 02 Jul

Staff, 1995). The crop yield and plant population data from 1989 to 1996 were collected as part of this study. The soil loss rates were determined using USLE (Walker and Pope, 1983). 2.3. Statistical analysis Statistical analysis for all parameters were performed using the procedures from Statistical Analysis System (SAS) computer software (SAS Institute, 1995). Analysis of variance, least-square means of selected variables, and covariance analysis using plant population (in the case of crop yield) were performed by general linear model (GLM) procedures.

Jun Jun Jun Jun Jun

May May May May

Jun Jun Jun Jun

3. Results and discussion 3.1. Crop residues and estimated erosion The no-till system maintained a signi®cantly higher amount of residue on the soil surface as compared with that of the CP and MP systems during each year at planting (Table 4). Crop residue on the soil surface was higher with maize as previous crop, compared with that of soybean because of higher residue production from maize and lower rate of decomposition of maize residue (Lueschen et al., 1991) than soybean residue. On Grantsburg soil with 5±7% slopes, the estimated annual soil loss, measured with USLE, was

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I. Hussain et al. / Soil & Tillage Research 52 (1999) 37±49

Table 4 Effect of different tillage treatments on plant residue after planting and soil loss at Dixon Springs Tillage

No-till Chisel plow Moldboard plow a b

Residue present from previous crop (% cover)a 1993

1994

1995

1996

75a 21b 6c

95a 47b 17c

76a 22b 6c

91a 18b 6c

7.9c 21.1b 29.5a

For each year, means within the same column followed by the same letter are not significantly different at the p ˆ 0.05 probability level. Soil loss is calculated by the universal soil loss equation (USLE).

7.9, 21.1, and 29.5 Mg haÿ1 with the NT, CP and MP systems, respectively (Table 4) (Walker and Pope, 1983). The higher the percentage of crop residue (Table 4) on the soil surface with the NT system protected the soil from erosion and kept it below the tolerance level of 8.4 Mg haÿ1 yearÿ1 (Walker and Pope, 1983). On the other hand, rill erosion was observed with the MP and CP systems due, in part, to less residue on soil surface compared with that of the NT system. 3.2. Soil responses During the 1995 growing season, differences in plant-available water due to tillage systems were non-signi®cant for all depths on all sampling dates (Table 5). The NT plots had a slightly higher plantTable 5 Tillage effects on plant available water at different depths during 1995 at Dixon Springs Tillage

Plant available water (cm3 of water per cmÿ3 of soil) a soil depth (cm) 0±15

15±45

45±75

Twenty-five days after planting (22 Jun 1995) No-till 0.22a 0.20a Chisel plow 0.19a 0.20a Moldboard plow 0.18a 0.18a

0.17a 0.19a 0.16a

Midseason (26 Jul 1995) No-till 0.07a Chisel plow 0.11a Moldboard plow 0.07a

0.10a 0.10a 0.10a

a

Soil loss (Mg haÿ1) b

0.05a 0.04a 0.06a

For each date, means within the same depth followed by the same letter are not significantly different at the p ˆ 0.05 probability level.

available water compared with that of the CP and MP plots in the 0±15 cm and the 15±45 cm soil layers at 25 days after planting. The CP system had more plantavailable water in the 45±75 cm soil layer than NT and MP systems. The amount of plant-available water was equal in the 45±75 cm layer in all tillage systems at midseason in 1995, but the CP system stored more water compared with that of the NT and MP systems in the 0±15 cm soil layer. The lower amount of plantavailable water with the NT system compared with that of CP system at midseason 1995 could be the result of higher plant population with the NT and MP systems compared with that of the CP system (Table 6). Plant-available water was lower at midseason than 25 days after planting in all tillage systems due to higher requirements of water by plants at this stage (Table 6), more potential evaporation of water from soil due to higher temperature, and below average rainfall (9.1 cm) between 25 days after planting and midseason sampling. After midseason sampling, maize received 9.0 cm of rainfall from tasseling to the harvest of the crop. During the 1996 growing season, non-signi®cant differences between tillage systems were observed in plant-available water at all depths on all sampling dates (Table 7). The NT system plots contained more plant-available water at planting, 25 days after planting, and at midseason than did the MP system plots in the 0±15, 15±45 and 45±75 cm soil layers. At planting and 25 days after planting, plant-available water differences between tillage systems were not pronounced due to abundant rainfall (Table 8) between, and around, the sampling dates. Later in the season, there was no rainfall from August 2 to 15, which resulted in 0.03 cm3 of plant-available water per cmÿ3 of soil with the NT system, while the MP and the CP systems had 0.01 cm3 of plant-available water per cmÿ3 of soil

I. Hussain et al. / Soil & Tillage Research 52 (1999) 37±49

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Table 6 Effect of different tillage treatments on the maize and soybean population during 1989±1996 at Dixon Springs Tillage

Maize No-till Chisel plow Moldboard plow

Soybean No-till Chisel plow Moldboard plow a b

Plant population (plants haÿ1)a 1989

1991

1993

1995

Averageb

55 300 59 200ab 62 900a

57 900 47 400b 52 200ab

51 400 54 100a 52 600a

58 800 55 700b 62 200a

55 800 54 100b 57 500a

1990

1992

1994

1996

Averageb

191 000b 247 000a 249 000a

344 000a 335 000a 343 000a

303 000a 229 000b 181 000c

263 000b 277 000b 309 000a

276 000a 272 000a 270 000a

For each crop, means within the same year followed by the same letter are not significantly different at the p ˆ 0.05 probability level. Four-year average.

in the 0±15 cm soil layer at midseason sampling. In the 15±45 and 45±75 cm soil layers plant-available water was also higher in the NT compared with that of the MP system. The 1996 soybean crop received suf®cient rainfall from June 26 (25 days after planting) to August 15 (midseason), but rainfall during August was below average. Plant-available water was lower at Table 7 Tillage effects on plant available water at different depths during 1996 at Dixon Springs Tillage

Plant available water (cm3 of water per cmÿ3 of soil) a soil depth (cm) 0±15

15±45

45±75

0.19a 0.18a 0.18a

0.16a 0.14a 0.15a

Twenty-five days after planting (26 Jun 1996) No-till 0.16a 0.19a Chisel plow 0.16a 0.18a Moldboard plow 0.15a 0.17a

0.16a 0.16a 0.16a

Midseason (15 Aug 1996) No-till 0.03a Chisel plow 0.01a Moldboard plow 0.01a

0.13a 0.11a 0.11a

At planting (6 Jun 1996) No-till 0.21a Chisel plow 0.16a Moldboard plow 0.18a

a

0.09a 0.09a 0.08a

For each date, means within the same depth followed by the same letter are not significantly different at the p ˆ 0.05 probability level.

midseason compared with that at earlier dates in the 0± 15, 15±45 and 45±75 cm soil layers due to the high water requirement of the crop at midseason. Although the amount of available water was low in the 0±15 and 15±45 cm soil layers at midseason in all tillage systems, rainfall of 16.3 cm to the end of September provided enough plant-available water for later stages of soybean growth. The availability of slightly more water with the NT system compared with that of the CP and the MP systems could be attributed to the suppression of evaporation, more in®ltration, and lower runoff which resulted in more water conservation due to the presence of more residue on the soil surface (Table 4). The eroded Grantsburg soils can store 15 cm of water in the 75 cm of soil (Table 4) above a root-restricting fragipan. Maize needs 100 cm of water from storage and re-charge by rain for optimum production (Troeh et al., 1980). Soil temperatures (average daytime temperatures) were recorded at 25 days after planting of the crop in 1995 and 1996. During both years, the MP and CP systems had a higher soil temperature compared with that of the NT system. In 1995, the differences in soil temperature were non-signi®cant between tillage treatments, while the differences were signi®cant in 1996 (Table 9). The lower NT temperatures in 1995 and 1996 were probably due to the presence of more water and higher amount of residue on the soil surface (Table 9). The differences in soil temperature were signi®cant (p ˆ 0.05) in 1996 probably due to the higher amount of residue on soil surface by a preced-

44

I. Hussain et al. / Soil & Tillage Research 52 (1999) 37±49

Table 8 Rainfall data during the growing season from 1989 to 1996 at Dixon Springs in southern Illinois Year

Rainfall (cm)

1989 1990 1991 1992 1993 1994 1995 1996 1989±1996 average 30-Year average

Apr

May

Jun

Jul

Aug

Sep

6.1 14.5 12.5 6.1 12.3 16.2 17.7 14.8 12.5 11.2

4.1 28.2 8.9 6.7 13.0 1.5 22.0 14.2 12.3 12.4

14.3 4.4 1.8 7.6 17.8 10.2 15.2 9.0 10.0 9.8

12.8 6.4 3.7 13.4 13.4 6.0 7.3 13.1 9.5 10.3

10.0 10.5 4.0 3.9 10.9 9.8 8.2 1.4 7.3 8.6

4.6 8.8 12.4 19.1 19.4 7.0 4.8 14.8 11.4 7.8

ing maize crop (Table 4). The soil temperature needs to be 428C for germination and an air temperature of 628C is optimum for the growth of maize (Illinois Agronomy Staff, 1992). 3.3. Crop responses Maize plant heights were greater with the NT system than the CP and MP systems at 25 days after planting and at midseason during 1995 (Table 9), due in part to higher plant-available water at 25 days after Table 9 Effect of different tillage treatments on soil temperature and plant height at Dixon Springs Tillage

Soil temperature (8C)a 1995

1996 b

No-till Chisel plow Moldboard plow

25 DAP

25 DAP

24.3a 24.4a 24.5a

21.0b 22.1a 22.1a

Plant height (m)a

No-till Chisel plow Moldboard plow a

1995

1995

1996

25 DAP

midseason

midseason

0.70a 0.61b 0.61b

3.02a 2.90b 2.80c

0.89a 0.84a 0.90a

Means for same date and parameter followed by the same letter are not significantly different at the p ˆ 0.05 probability level. b 25 DAP represents 25 days after planting.

planting. Other factors that might have contributed to the taller plants with the NT system were a less competition between plants due to lower population or better nutrients and water availability due to protection from erosion with NT system than with the CP and MP systems. During 1996, the soybean plant height was not recorded at 25 DAP due to the smaller size of soybean than maize at this stage. By the midseason, no signi®cant differences were observed in soybean height due to tillage. The data from the tissue analysis of maize (1995) and soybean (1996) leaves at midseason (Table 10) showed non-signi®cant differences in concentration of all elements except N in 1995 for maize due to tillage. Moldboard plowing was associated with a higher maize leaf nitrogen concentration compared with that of the leaves in the CP and NT systems. This might indicate lower nitrogen immobilization and higher mineralization with the MP system than with the NT or CP systems. Plant uptake of other macroand micro-nutrients was not affected by tillage in either year (Table 10). This is consistent with the fact that there were no tillage based differences in plantavailable water. Rainfall data (30-year average for southeastern Illinois) and 1989±1996 growing seasons are shown in Table 8. The 30-year average cumulative rainfall during April±September in southeastern Illinois was 60.1 cm. During the study, half of the years (1989, 1991, 1992 and 1994) could be characterized as dry years with a growing season rainfall of 51.9, 43.3, 56.8, and 50.7 cm, respectively. The years with the most below-average rainfall were 1991, and 1994. In

I. Hussain et al. / Soil & Tillage Research 52 (1999) 37±49

45

Table 10 Effect of tillage on maize and soybean tissue analysis at midseason in 1995 and 1996 at Dixon Springs Tillage

Nutrientsa (g kgÿ1) N

P

S

K

Mg

Maize (1995) No-till Chisel plow Moldboard plow

32.6a 31.8a 34.0b

3.6a 3.6a 3.6a

1.9a 1.9a 2.0a

22.0a 22.9a 22.6a

1.5a 1.7a 1.6a

Soybean (1996) No-till Chisel plow Moldboard plow

60.0a 61.1a 61.4a

4.1a 4.1a 3.8a

3.3a 3.3a 3.3a

17.0a 16.8a 16.2a

3.3a 3.2a 3.2a

a

Ca

Na

B

Zn

Mn

Fe

Cu

Al

4.6a 4.5a 4.4a

0.1a 0.1a 0.1a

0.005a 0.005a 0.006a

0.021a 0.021a 0.022a

0.056a 0.068a 0.067a

0.115a 0.114a 0.117a

0.012a 0.011a 0.012a

0.062a 0.058a 0.060a

15.2a 14.2a 14.8a

0.1a 0.1a 0.1a

0.049a 0.045a 0.043a

0.053a 0.054a 0.052a

0.109a 0.118a 0.122a

0.141a 0.152a 0.163a

0.013a 0.013a 0.012a

0.063a 0.062a 0.072a

Means for the same year and nutrient followed by the same letter are not significantly different at the p ˆ 0.05 probability level.

1991, the driest year, the maize yields were low for all treatments since all plant-available water above the fragipan was extracted from all treatments, including the NT system. In 1994, another year of low rainfall, the soybean yields were low for all treatments, but NT yield was substantially higher than CP and MP yields. The eight-year average rainfall for the April through September period was 63.0 cm which is slightly above the 30-year average. From 1989 to 1996, the MP system had a signi®cantly higher plant population in four out of eight years (Table 6) and the NT system had a signi®cantly higher plant population in two out of eight years. In 1989, the NT had a lower plant population (Table 6) compared with that of the MP system which was probably due to insuf®cient soil±seed contact, lower germination, and greater soil strength in the NT system (Kitur et al., 1994). During 1990, 1995, and 1996, the high April and May rainfalls contributed toward lower plant population with the NT system compared with that of the MP system (Table 6). Higher plant population with the MP system than with the NT and CP systems during 1995 and 1996 was also observed. Higher soil temperature and better seed±soil contact with the MP system could have increased the germination compared with that of the NT system during 1995 and 1996. On the other hand, in 1994, the plant population was higher with the NT treatment compared with that of the CP and the MP treatments, which could have been due to relatively greater water availability in the NT system compared with other tillage systems at planting. Four-year average plant population (Table 6) for maize was higher with the NT

system compared with that of the MP and CP systems, while the four-year average soybean population was not affected by tillage treatment. From 1989 to 1996, tillage affected crop yields only in the years 1989 and 1994 (Table 11). Because of the higher plant population (Table 6) with the MP system, in four out of eight years, plant population was used as a covariant in the yield analysis. For maize yields, plant population was signi®cant as a covariant, but the improvement in r2 was only from 0.77 to 0.78. For the soybean yield analysis, plant population was not signi®cant as a covariant. Plant population adjusted crop yields are presented in Table 12. Maize yield was highest for the MP system in the years 1989 and 1991 (Table 12), with the higher yield in early years believed to have been due to better seed±soil contact, germination, lime incorporation, weed control, and mineralization of organic matter (Kitur et al., 1994). The NT maize yields in 1993 and 1995 were higher than the CP and the MP systems and differences were signi®cant in 1995 due to slightly more water and better protection from erosion. The MP system produced a higher soybean yield than the NT and CP systems in 1990, but later on, soybean yields with the NT system improved compared with the MP system. In 1992, 1994 and 1996, the NT system produced a higher soybean yield. Soybean yield with the NT system was higher than with the CP and MP systems due to better plant population in 1994. Since 1994 was a dry year, the NT system could have provided more soil water to soybean at planting and later in the season compared with that of the other tillage systems. This enhanced

46

I. Hussain et al. / Soil & Tillage Research 52 (1999) 37±49

Table 11 Effect of different tillage treatments on maize and soybean yield during 1989±1996 at Dixon Springs Tillage

Maize No-till Chisel plow Moldboard plow

Soybean No-till Chisel plow Moldboard plow a b

Crop yield (Mg haÿ1)a 1989

1991

1993

1995

Averageb

8.99b 9.99b 11.26a

6.57a 6.10a 6.60a

11.79a 11.61a 10.98a

11.60a 11.55a 10.37a

9.81a 9.74a 9.80a

1990

1992

1994

1996

Averageb

2.37a 2.62a 2.62a

3.74a 3.46a 3.65a

2.87a 1.81b 1.49b

2.63a 2.27a 2.43a

2.90a 2.54b 2.55b

For each crop, means within the same year followed by the same letter are not significantly different at the p ˆ 0.05 probability level. Four-year average.

soil-water storage could have resulted in an improvement in nutrient availability and played an important role in 100% and 60% higher soybean yields with the NT system as compared to MP and CP systems in 1994. Higher crop yield with the NT system than with the MP system in a dry year was also noted by Lueschen et al. (1991). Although the differences in soybean yields in 1996 were not signi®cant by tillage treatment, the NT system had a 7% and 15% higher yield than the MP and CP systems, respectively. Higher yield with NT in the 1996 season was attributed to better plant growth, more soil water, higher organic matter content in the 0±5 cm layer, and more protection from erosion as compared with MP.

The four-year average maize yield was not affected by tillage, while the four-year average soybean yield was higher with NT than with CP and the MP (Table 10). Four-year average soybean yield was 14% higher with NT than with CP and MP systems, while the maize yield was equal in all tillage systems. At the beginning of the experiment, the MP system produced 21% and 11% higher yield compared with that of the NT and CP systems during 1989 and 1990 but with no difference in 1991. After three years, the NT system yields were 3±100% higher than the MP system (Fig. 1) during the 1992±1996 period. The NT yields were lower in the early years of study, but improved with the passage of time. The NT

Table 12 Effect of different tillage treatments on the covariate (plant population) adjusted maize and soybean yields during 1989±1996 at Dixon Springs Tillage

Maize No-till Chisel plow Moldboard plow

Soybean No-till Chisel plow Moldboard plow a b

Crop yield (Mg haÿ1)a 1989

1991

1993

1995

Average b

8.98b 9.77b 10.85a

6.45a 6.53a 6.78a

11.99a 11.66a 11.13a

11.37a 11.49a 9.95b

9.69a 9.86a 9.68a

1990

1992

1994

1996

Averageb

2.33a 2.60a 2.61a

3.78a 3.50a 3.68a

2.89a 1.79b 1.44b

2.62a 2.27a 2.45a

2.90a 2.54b 2.55b

For each crop, means within the same year followed by the same letter are not significantly different at the p ˆ 0.05 probability level. Four-year average.

I. Hussain et al. / Soil & Tillage Research 52 (1999) 37±49

47

Fig. 1. Relationship of NT ÿ MP yield difference and growing season rainfall over time.

performance relative to MP and CP was better during dry years than wet years, which was also observed by Eckert (1984). Figs. 1 and 2 show the yield trend of conservation tillage compared with the MP system with growing season rainfall (April±September) over time. The percentage change was calculated using the following equations: ‰…NT ÿ MP†=MPŠ  100;

(1)

(see Fig. 1), and ‰…CP ÿ MP†=MPŠ  100

(2)

(see Fig. 2). 3.4. Rainfall effects The NT yields were lower during the three early years of the study. This could have been due to lower organic carbon and nitrogen mineralization and higher immobilization of soil nitrogen with the NT than the MP system (Rice and Smith, 1984), but the NT system out-yielded the MP system during the last ®ve years of study. No-till yields were 5±20% lower than the MP

system in wet years, but were 10±100% higher in relatively dry year (Fig. 1) and NT ÿ MP was negatively correlated (r2 ˆ ÿ0.66, p ˆ 0.07) with growing seasonal rainfall. The higher yields with the NT and CP systems in dry years was probably due to the conservation of more soil water than in the MP system, while yields with the NT and the CP systems were lower compared to that of the MP system in wet years (Fig. 1). The CP yields were lower in the ®rst four years compared to that of the MP system and the CP system out-yielded the MP system from 1993 to 1995 period. Chisel plow yields were 5±10% lower in wet years and 20% higher in dry years as compared to MP system (Fig. 2). The CP ÿ MP difference was negatively correlated (r2 ˆ ÿ0.56, p ˆ 0.15) with growing seasonal rainfall. Generally, well-distributed rainfall over the growing season resulted in better yields for both, maize and soybean with all tillage systems. Water de®ciency or heavy rains in May could have resulted in yield losses by reducing plant population. Higher rainfall during July and August played a critical role in improving the yield of maize and soybean, which

48

I. Hussain et al. / Soil & Tillage Research 52 (1999) 37±49

Fig. 2. Relationship of CP ÿ MP yield difference and growing season rainfall over time.

was evident from yield responses in 1989, 1990, 1992, 1994 and 1996. 4. Conclusions Conservation tillage, especially in the NT system, left more crop residue on the soil surface and provided protection to soil from water erosion as against the MP system. During the 1995 and 1996 growing seasons, NT resulted in taller plants, slightly more plant-available water, and lower soil temperature at 25 days after planting. Non-signi®cant differences in all elemental concentrations in leaf except nitrogen were observed due to tillage treatments during 1995 and 1996, suggesting no tillage effects on the uptake of nutrients by plants. Nitrogen concentration in leaves was higher in MP system plots compared with that of CP and NT system plots. Although plant population was higher in the MP system during both years, crop yields were higher in the NT system compared with that of the MP system which was probably due to more plant-available water and less erosion. The plant population in NT system which was affected by the lower soil

temperature and poor soil±seed contact during the early growing season. In the ®rst year, crop yield was higher in the MP system compared with that of the CP and NT systems; however, the NT system produced higher crop yields during the last ®ve years. Tillage did not affect fouryear average yield or plant population of maize. Fouryear average soybean plant population was not affected by tillage; however, the four-year average soybean yield was higher in the NT system compared with other tillage treatments. Maize yields were equal in all tillage systems as a result of higher MP system yield in the ®rst year, which offset higher CP and NT systems yields during the last two years. Soybean yield was 15% higher in the NT system in comparison with the CP and MP systems. Higher NT soybean yields could be due to a higher amount of residue from previous year's maize, which improved water conservation. Crop yields were higher in the NT system despite lower plant population, so greater water and nutrient availability per plant may have compensated for the effect of lower plant population. The NT system performed better in dry years by conserving water and the NT yield improved over time. Based on

I. Hussain et al. / Soil & Tillage Research 52 (1999) 37±49

eight years of crop yield measurements (four years maize and four years soybean), the NT system appears to have resulted in improved long-term productivity compared with that of the MP and CP systems. The results of this study should be applicable to similar root-restricting, sloping, and moderately eroded soils in Illinois, Indiana, Missouri, and Kentucky. References Aase, J.K., Tanaka, D.L., 1987. Soil water evaporation comparisons among tillage practices in the Northern Great Plains. Soil Sci. Soc. Am. J. 51, 436±440. A&L Laboratory Staff, 1995. Plant analysis. A&L Lakes Laboratories, Inc. Fort Wayne, IN, pp. 15. Alberts, E.E., Neibling, W.H., 1994. Influence of crop residue on water erosion. In: Unger, P.W. (Ed.), Managing Agricultural Residues. Lewis Publishers, Boca Raton, FL, pp. 19±44. Carlson, R.E., 1990. Heat stress, plant-available soil moisture and corn yield in Iowa: a short- and long-term view. J. Prod. Agric. 3, 293±297. Cochran, W.G., Cox, G.M., 1957. Experimental Design, second ed. John Wiley & Sons. New York, pp. 615. Dick, W.A., Van Doren Jr., D.M., 1985. Continuous tillage and rotation combinations effects on corn, soybean, and oat yields. Agron. J. 77, 459±465. Dickey, E.C., Pasha, J.P., Grisso, R.D., 1994. Long-term tillage effects on grain yield and soil properties in a soybean/grain sorghum rotation. J. Prod. Agric. 7, 465±470. Dickey, E.C., Shelton, D.P., Jasa, P.J., Peterson, T.R., 1985. Soil erosion from tillage systems used in soybean and corn residues. Trans. ASAE. 28, 1124±1129. Dudal, R., 1970. Key to soil units for the soil map of the world. Soil Res. Dev. and Can. Serv. Land and Water Dev. Div. FAO, Rome, Italy, pp. 125. Eckert, D.J., 1984. Tillage system planting date interactions in corn production. Agron. J. 76, 580±582. Hill, P.R., Manning, J.V., Wilcox., J.R., 1989. Estimating corn and soybean residue cover. Agronomy Guide. Purdue Univ. Coop. Extn. Serv. W. Lafayette, IN. House, G.F., Stinner, B.R., Crosseley Jr., D.A., Odum, E.P., Langdale, G.W., 1984. Nitrogen cycling in conventional and no-tillage agroecosystems. J. Soil Water Cons. 39, 194±200. Illinois Agronomy Staff, 1992. Illinois Agronomy Handbook. Circular 1321. Illinois Cooperative Extension Service, University of Illinois, Urbana, IL, pp. 138. Ismail, I., Blevins, R.L., Frye, W.W., 1994. Long-term tillage effects on soil properties and continuous corn yields. Soil Sci. Soc. Am. J. 56, 1244±1249. Kapusta, G., Krausz, R.F., Matthews, J.L., 1996. Corn yield is equal in conventional, reduced, and no tillage after 20 years. Agron. J. 88, 812±817. Karlen, D.L., Berry, E.C., Colvin, T.S., 1991. Twelve year tillage

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