Soil & Tillage Research, 7 (1986) 19--28 19 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands

THE EFFECT OF REDUCED SOIL TILLAGE ON MAIZE (ZEA MA YS L.) GRAIN YIELD IN EASTERN CROATIA (YUGOSLAVIA)

IVAN ~UGEC Institute o f Agriculture, Biotechnical Research and Teaching Centre, University of Osijek, Tenjska cesta bb, 54000 Oso'ek (Yugoslavia)

(Accepted for publication 20 August 1985)

ABSTRACT

~ugec, I., 1986. The effect of reduced soil tillage on maize (Zea mays L.) grain yield in eastern Croatia (Yugoslavia). Soil Tillage Res., 7: 19--28.

The effect of reduced soil tillage on the yield of maize after winter wheat was studied on 2 different soil types (i) meadow chernozem non-calcareous soil (Osijek) and (ii) level pseudogley (FeriiSanci). On both soil types, the highest and the most stable maize grain yields were obtained with conventional tillage, i.e. immediate post-harvest shallow ploughing to 10--15-cm depth in July, au tumn ploughing to 30--35-cm depth at the end of September, spring harrowing of the winter furrow in February or March and at planting in April, discing, Rau-combination system and conventional planting (Treat- ment 1).

In comparison with conventional tillage, immediate post-harvest ploughing to 30--35- cm depth in July (Treatment 6), and immediate post-harvest shallow ploughing to 10--15- cm depth without autumn ploughing (Treatment 4), both coupled with conventional tillage and spring planting as in Treatment 1, as well as direct drilling into a post-harvest shallow ploughed field without autumn ploughing (Treatment 5), resulted on average in slightly lower yields on meadow chernozem soil in 1979--1982 and on pseudogley in 1979--1981.

On both soil types, slightly lower yields were obtained with autumn ploughing to 30--35-cm depth at the end of September (Treatment 3) and on pseudogley, with spring ploughing to 20--25-cm depth in February or March (Treatment 2). In both treatments, the post-harvest shallow ploughing was omitted; conventional seedbed preparation was the same as in Treatment 1. On meadow chernozem soil, spring ploughing (Treat- ment 2) resulted in a highly significant yield reduction (23%).

Spring discing to 5--8 cm at seedbed preparation in April (Treatment 7), and the complete elimination of tillage, i.e. zero tillage (Treatment 8), proved to be totally un- acceptable because of high reductions in maize grain yield on both soil types.

INTRODUCTION

In Yugoslavia , ma ize (Zea mays L.) is g rown on m o r e t h a n 2 mil l ion ha, i.e. on a p p r o x i m a t e l y 30% o f t he to t a l a rea o f f a rmland . In t he com- m o n c r o p r o t a t i o n , m a i z e usual ly fo l lows win te r w h e a t and in this case

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conventional tillage for maize consists of post-harvest shallow (10--15 cm) ploughing, deep (35 cm) autumn ploughing and seedbed preparation with discs and combined implements. Under the agro-ecological conditions of Slavonia (eastern Croatia), this tillage system ensures high and stable yields, but at the same time it entails high costs and high energy consump- tion, as well as many machine- and man-hours. In addition, it has a number of adverse effects on the soil, such as compaction caused by wheel traffic.

The factors mentioned above have given impetus to research into more efficient methods of soil tillage, both in large-scale production and in agri- cultural research institutions. One of the possible means of attaining this goal is simplified, reduced soil tillage, which consists either of a reduced number of tillage operations and/or a reduced tillage depth.

Studies of reduced tillage reported in the literature have not given uniform results. Comprehensive studies of minimum tillage and zero tillage in the U.S.A. have shown that minimum tillage and zero tillage are applicable only under certain climatic and soil conditions. Van Doren and Triplett (1969, 1973), Griffith et al. (1973), Van Doren et al. (1976), Mock and Erbach (1977), Elkins et al. (1979) and a number of other researchers in the U.S.A. have shown that zero tillage gives good results on soils with favourable physical properties, on weU-drained silt loam, with planting in the mulch of sod, with the application of dead mulch and with appropri- ate herbicide application. On the other hand, minimum and zero tillage do not give as high yields as conventional tillage on soils with unfavourable physical properties and unstable structure, on poorly-drained clay loam and clay soils and on soils with unfavourable temperature regimes.

Workers in other countries have arrived at similar conclusions. Vyn et al. (1979, 1982) carried out detailed studies of reduced tillage systems in Canada and concluded that in southern Ontario zero tillage resulted in substantial yield reductions (3--16%), which were mainly due to the deteri- oration of soil physical properties. However, experiments with discing and chisel ploughing have shown that there are acceptable methods of reduced soil tillage.

Recent experiments with reduced tillage and zero tillage in Europe have been conducted by Stojnev (1969), Szipozs (1972), Kahnt (1976), Sin et al. (1979), Christov (1982) and also by a number of researchers in Yugo- slavia, e.g. Kosovac (1972), Drezgid et al. (1972), Stojkovid et al. (1975), Drezgid (1976), Milojid et al. (1976), Butorac et al. (1976, 1979, 1981a,b), Mihalid (1978), KolCar and Videnovid (1982), Konstantinovid (1982), and Videnovid (1982). The results of the majority of these workers show that the complete elimination of soil tillage gives the least acceptable results because it drastically diminishes maize yields. Somewhat better results were obtained with discing only and with rotary implements. Some of these workers have obtained even better results with shallow ploughing, deep discing and chisel ploughing, especially when soil tillage methods were used in combination with intensive, deep tillage in the preceding years.

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One of the most important research results was the realization that reduced tillage, and to some extent zero tillage, may be successful when applied occasionally (for 1 or 2 years), alternating with intensive, conven- tional tillage, but not as a cont inuous method of soil tillage. Moreover, methods of reduced tillage and zero tillage are suitable only for some crops and for soils with a favourable mechanical composi t ion and structure, and a good supply of nutrients.

Although maize is grown in eastern Croatia, i.e. in Slavonia and Baranja on more than 200 000 ha (30% of the total area of farmland), the applica- tion of different methods of reduced soil tillage has not been sufficiently studied in this region. For this reason, experiments with reduced soil tillage were conducted on two different soil types. The results of these experiments with respect to maize grain yield are reported in this paper.

MATERIALS AND METHODS

Climate and weather conditions

The Slavonia and Baranja regions are located in a transitional area between the semi-arid, temperate continental-climate zone of Eastern Europe and the semi-humid temperate continental climate zone of Central Europe. The eastern part of the region (Osijek) is more arid (699 mm rainfall year-~), whereas the western part (Ferieanci) has a more humid climate (843 mm rainfall year-l) . Lang's rain factors for Osijek and FeriCanci are 64 and 80, respectively.

In the first year of the experiment (1979), the spring was very dry and warm, but in 1980 the spring was extremely wet. The third and the fourth year of the experiment were medium-wet during the warm part of the year (Table I).

So ils

Two soil types were included in the experiment; fertile meadow cherno- zem non,calcareous soil (Osijek) and level pseudogley, which has a lower productive capacity (Ferieanci). The meadow chernozem soil has a crumbly structure in the plough layer. Pseudogley on level terrain has all the charac- teristics typical of this soil type, i.e. it has an unfavourable water--air regime with quick changes of the dry and wet phase, rather light mechanical com- position in the plough layer and an unstable, powdery structure. The soil profile shows differentiated texture and the soil is prone to slaking and crust formation under adverse weather conditions. The chemical properties of the soil are given in Table II.

Tillage methods, fertilization and crops

Experiments with 8 different soil tillage systems (Table III) and 3 fertil- izer rates were conducted over a period of 4 years (1979--1982) on meadow

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TABLE I

Precipitation and mean air temperature for the growing season in the years 1979--1982

Year Location Month

April May June July Aug.

Total

Sept.

Precipitation (ram) 1979 Osijek 35 11 49 92 59 21 267

Feri~anci 49 3 95 123 105 42 417 1980 Osijek 93 100 76 58 66 16 409

Feri~anci 134 121 80 22 52 30 439 1981 Osij ek 28 22 180 28 50 65 373

Feri~anci 34 84 94 25 49 90 376 1982 Osijek 71 31 59 80 97 23 361

Average Os~ek 62 69 83 60 56 53 383 1901--1980 Feri~anci

77 81 93 69 74 64 458 1925--1980

Temperature (°C) 1979 Osijek 10.0 17.4 22.0 19.6 19.8 16.7 --

Feri~anci 10.5 15.8 21.5 19.6 19.8 16.8 -- 1980 Osij ek 8.2 13.4 19.2 19.7 20.0 15.9 --

Feri~anci 7.7 12.3 18.4 19.6 19.6 16.4 -- 1981 Osijek 11.2 16.3 20.1 20.4 20.3 17.2 --

Feri~anci 11.0 14.6 19.7 20.4 19.1 16.7 -- 1982 Osijek 8.1 17.1 20.6 21.5 20.6 20.0 --

Average Osijek 1901--1980 11.2 16.2 19.6 21.4 20.6 16.6 --

Feri~anci 10.7 15.3 18.2 20.0 20.0 15.9 -- 1956--1980

TABLE II

Chemical soil propert ies

Soft type pH in IN KC1 P2Os--A1 K20--A1 Organic, Total N Saturat ion (100 g of (100 g of mat te r (%, w/w) of adsorpt ion soil) soil) (%, w/w) complex (%)

Meadow chemozem 5.3--6.4 9.5 16.5 1.8 0.13 80.7 Pseudogley 4.8 16 16 1.4 0.10 65 .9

c h e r n o z e m n o n , c a l c a r e o u s soil (Os i j ek ) , a n d o v e r a p e r i o d o f 3 y e a r s ( 1 9 7 9 - -

1 9 8 1 ) o n l eve l p s e u d o g l e y ( F e r i e a n c i ) . T h e f o l l o w i n g f e r t i l i z e r r a t e s w e r e a p p l i e d :

(a) C o n t r o l (F0): n o f e r t i l i z e r

(b) L o w r a t e (F~): N : P 2 O s : K 2 0 = 1 4 0 : 1 2 0 : 1 6 0 kg ha -~

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TABLE III

Cultivation treatments for maize

Treatment Summer Autumn Spring

1 a Post-harvest shallow Ploughing ploughing (10--15 cm): straw to 30--35 cm chopped and ploughed under

Stubble field, straw removed without tillage in summer

Stubble field with straw, without tillage in summer

Post-harvest shallow ploughing (10--15 cm); straw chopped and ploughed under Post-harvest shallow ploughing to 10--15 cm, straw chopped and ploughed under Ploughing to 30--35 cm, straw chopped and ploughed under

Straw burnt in the field, without tillage in summer

8 Straw burnt in the field, -- without tillage in summer

Ploughing to 30--35 cm, straw chopped and ploughed under

Harrowing of winter furrow b, discing, Rau- combination system c, conventional planting Ploughing to 20--25 cm, discing, Rau-combination system, conventional planting Harrowing of winter furrow, discing, Rau- combination system, conventional planting

Discing, Rau-combination system, conventional planting Spraying with paraquat, planting with no-till planter Harrowing of winter furrow, discing, Rau- combination system, conventional planting Discing, Rau-combination system, conventional planting Spraying with paraquat, zero tillage, planting with no-till planter

aConventional tillage. bWinter furrow was harrowed only on the meadow chernozem CRau-combination system = combination of harrow and roller.

soil in Osijek.

(c) Med ium ra te (F2): N :P2Os :K20 = 1 6 0 : 1 3 8 : 1 8 2 kg h a - ' (d) High ra te (F3): N:P2Os:K~O = 1 8 0 : 1 5 5 : 2 0 5 kg h a - '

Di rec t dril l ing {Trea tmen t s 5 and 8) were p e r f o r m e d wi th a special p l an t e r (MSK, p r o d u c t o f O L T Osijek), a d a p t e d f r o m the m o d e l o f the J o h n Deere no-til l p l an te r , w i th zig-zag disc opene r s in f r o n t o f the p l an t ing coul ters . O t h e r t r e a t m e n t s were p l an t ed wi th conven t iona l ma ize p lanters . Af te r p lan t ing , all t r e a t m e n t s rece ived 3 1 h a - ' Radaz in and 4 1 h a - ' Lasso (a.i. 50% a t raz ine and 50% a lachlor , respec t ive ly) fo r weed con t ro l .

The ma ize h y b r i d OsSK 407 ( F A O m a t u r i t y 400) was used in all ex- p e r i m e n t s e x c e p t fo r t h a t o f 1980 , when on pseudog ley , due to la te p lan t - ing, OsSK 247 ( F A O m a t u r i t y 200) had to be used. Fu radan (a.i. ca rbo-

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furane) was used for the control of wireworms (Elateridae). The basic plot size for tillage t reatments was 200 and 50 m 2 for fertilization treatments. Trials consisted of a split plot arrangement of a randomized block design with four replications. The preceding .crop in the experiments was always winter wheat. All experiments were conducted on the same field, but on a different part of the field each year.

RESULTS AND DISCUSSION

Due to limitations of space, the discussion will concentrate only on the most important maize grain yield indicators, which are shown in Table IV.

Both soil types reacted strongly to soil tillage t reatments in 1979, which was dry, and in 1981 and 1982, which were medium wet. In 1980, which was wet, relatively high yields were obtained with all tillage treatments on meadow chernozem soil, although even in this year some tillage treat- ments, i.e. Treatments 2, 5, 7 and 8, resulted in highly significant yield reductions in comparison to conventional tillage. On pseudogley, maize grain yields were very low, but there were different relationships between tillage treatments. Namely, in 1980 the highest yields on pseudogley were obtained with discing (Treatment 7), zero tillage (Treatment 8) and direct drilling after shallow post-harvest ploughing (Treatment 5). Presumably, this effect was due to favourable soil moisture and temperature (lower saturation of the soil with water), initial fertilizer placement into the soil beside the row and reduced immobilization of nutrients. Treatments with early-summer tillage without autumn ploughing, such as immediate post- harvest ploughing to 30--35-cm depth (Treatment 6) and shallow post- harvest ploughing coupled with conventional planting (Treatment 4), proved to be risky on pseudogley due to the high incidence of hydrophilic weeds, which delay and prevent normal seedbed preparation and planting.

On the whole, the results of the 4-year experiments on meadow cherno- zem soil and the 3-year experiments on pseudogley have shown that con- ventional tillage (Treatment 1) gives the highest and most stable yields on both soil types.

The omission of post-harvest shallow ploughing followed by autumn ploughing (Treatment 3) or spring ploughing (Treatment 2) resulted in yield reductions which were not always significant; this points to the pos- sible importance of these tillage practices. Autumn ploughing (Treatment 3) gave satisfactory yields on the fertile chernozem soft, but not on the pseudogley. This difference can be attributed to the omission of post- harvest shallow ploughing and higher weed incidence (ploughing under of weed seeds) during the growing season on pseudogley. Spring ploughing (Treatment 2) of meadow chernozem soil resulted in a highly significant yield reduction, which can be attr ibuted to a coarse seedbed, high weed incidence and a reduction in maize stands.

The omission of post-harvest cultivation in the case of immediate summer

25

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26

ploughing to 30--35-cm depth (Treatment 6) was effective on both soil types. The yields were only slightly lower in comparison to conventional tillage, which indicates that this tillage method is acceptable provided summer drought does not hinder its application.

Satisfactory results were also obtained when post-harvest shallow tillage to 10--15-cm depth without autumn ploughing was coupled with con- ventional planting (Treatment 4) as well as with direct drilling without ad- ditional soil tillage (Treatment 5). Yield reductions were within the limits of experimental error. They were due mainly to insufficient water and nutrient supply caused by the omission of autumn ploughing, insufficient accumulation and conservation of water in the soil and the fact that the lower strata of the ploughed layer where the major part of the root system is formed was not loosened.

Spring discing (Treatment 7) and zero tillage (Treatment 8) resulted in very large yield reductions which were due to high weed incidence, deteriora- tion of soil physical properties (increase in bulk density and penetrometer resistance, decrease in porosity and air capacity), slow and incomplete emergence, poor stands, insufficient water and nutrient supply, reduced growth and development of the maize and reduction in 100-liter and 1000- kernel weight.

CONCLUSIONS

(1) Maize grain yields in the system of reduced soil tillage were largely affected by the soil type and weather conditions. On both chernozem and pseudogley, the highest and the most stable yields were obtained with conventional tillage. The treatments involving reduced soil tillage resulted in yield losses which depended on the extent of conventional soil tillage reduction and agro-ecological conditions. Some methods of reduced soil tillage have proved to be acceptable both from the point of view of plant production and from the point of view of efficiency. These methods are: (a) immediate post-harvest ploughing to 30--35-cm depth; (b) post-harvest shallow tillage to 10--15-cm depth without the usual autumn ploughing to 30--35~m depth, coupled with conventional planting or direct drilling without additional seedbed preparation; (c) autumn or spring ploughing without post-harvest shallow tillage on pseudogley, and autumn ploughing on meadow chernozem soil. Spring ploughing has proved to be totally un- acceptable on meadow chernozem soil because of high yield reductions.

(2) The treatments involving a higher degree of soft tillage reduction such as spring discing to 5--8-cm depth or the complete elimination of soil tillage (zero tillage) drastically reduced maize grain yields and proved to be unacceptable under the ago-ecological conditions of this region, both from the point of view of plant production and the point of view of efficiency.

(3) Acceptable results with some reduced soil tillage treatments were

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obtained when reduced soil tillage was applied after intensive, deep tillage over a number of years on antropogenic softs which show residual effects of conventional tillage. This shows that reduced soil tillage can produce favourable effects only when applied for a short period of time and in succession with conventional tillage.

(4) Although a certain compensational effect of fertilization was ob- served in the interaction between soil tillage and fertilization, this effect was weakly pronounced and could not make up for the negative effects of reduced and zero tillage.

(5) This paper has concentrated only on the effect of tillage systems on maize development and yield. For a better judgement of these systems, further long-term experiments are needed with a number of crops in crop rotat ion under the different agro-ecological conditions of Croatia.

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