COMMUN. SOIL SCI. PLANT ANAL., 29(9&10), 1115-1131 (1998)
Barley Yield and Weed Development as Affected by Crop Sequence and Tillage Systems in a Semi-arid Environment José Dorado,a Cristina López-Fando,a and Juan Pablo Del Monteb a
Centro de Ciencias Medioambientales (CSIC), Serrano 115 Dpdo., E-28006, Madrid, Spain (e-mail address:
[email protected]) b Dpto. de Producción Vegetal, Botánica y Protección Vegetal, E.T.S.I.A., Universidad Politécnica, Ciudad Universitaria, E-28040 Madrid, Spain
ABSTRACT In order to monitor barley and weed development on a loamy sand soil subjected to different agronomic practices, field experiments were conducted for three growing seasons (1992-95) in a semi-arid agrosystem in central Spain. For eight years, independent plots were managed with three crop sequences: barley (Hordeum vulgare L.) vetch (Vicia sativa L.); barley sunflower (Helianthus annuus L.); and a barley monoculture. In all cases, two tillage systems were implemented: no-tillage and conventional tillage. In the years with standard rainfall (400 mm) an improvement in growthrelated cultivation variables and yield components of barley were observed in plots under barley vetch rotation and/or conventional tillage. In drier conditions (B), (ii) barley and sunflower (B-+S) in a 2-year rotation, and (iii) barley and vetch (B-»V) in a 2-year rotation. Sufficient numbers of plots were established so that each crop in each of the six treatments appeared each year (12 plots). The tillage variable is defined as follows: (i) no-tillage (NT) and (ii) conventional tillage (CT). Agronomic Management The CT plots were moldboard ploughed to a depth of 25 cm in the autumn (early October) followed by appropriate secondary tillage (harrowing to 10 cm depth) to prepare the seedbed for sowing. In the NT plots seed was sown directly
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DORADO, LÔPEZ-FANDO, AND DEL MONTE
into undisturbed soil with a triple-disk drill after spraying glyphosate herbicide [N-(phosphonomethyl)glycine] at 0.54 kg ha 1 broadcast in 150 L ha 1 . The date of sowing for barley and vetch depended on the timing of the autumn rains, usually in early November. At the start of the experiment, spring weed control was not carried out; hence, weed populations had favorable conditions to develop, and differences between treatments were enhanced. Barley (cv. Aramir) was sown to achieve a final population 250 plants m'2 (150 kg ha 1 ). Sowing depth was 5 cm and row spacing was 18 cm. At sowing, 500 kg ha 1 of NPK fertilization (8-15-15) were applied. Ammonium nitrate (33.5% N) was topdressed in the early spring (when the plants were in the first stages of stem extension) at a rate of 100 kg ha 1 . Barley was harvested in early July. Vetch was sown at 100 kg ha'1 with 10% oat (Avena sativa L.) to provide support. The vetch was harvested in May when it was flowering. Sunflower (cv. Toledo 2) was sown in April when the air temperature had risen to 7°C to achieve a final population of 40,000 plants ha 1 . Sowing depth was 3-5 cm and the crop was harvested in September. Crop Measurements and Analyses Seed depth for emerged barley seeds was estimated by measuring the white-stem length (first internode) above the seed. Plant density was measured at ZGS 13-21 (Zadoks et al., 1974) using four 0.25 m2 quadrants per plot. Dry matter production (DM) and NO3-N content were determined at 2-week intervals from seeding to grain ripening during the years 1992/3 and 1993/4, using the same procedure and sample area as for plant density. The plant material was dried ät 65°C and ground to pass a 1-mm screen. Plant NO3-N (ug g 1 ) was determined by a cadmium (Cd) reduction AutoAnalyzer method (Technicon Industrial Systems, 1973). In addition, plant samples of each barley plot collected at tillering (February), stem extension (March), heading (April) and ripening (May), were analyzed for total N, P, K, Ca, and Mg. Total N and P were measured using an AutoAnalyzer (Technicon) after semi-micro Kjeldahl digestion as described by Bremmer (1965) for N, and nitric-perchloric acid digestion for P (Inter-Institute Committee for the Study of Analytical Techniques on Foliar Diagnosis, 1969). Total K and Ca were determined by flame ionization photometry, whereas atomic absorption spectrophotometry was used for Mg. During the first cropping season (1992/93), the total leaf area (cm2 plant1) was measured at 2-week intervals using a foliar surface analyzer (Area Meter mk2). When barley was mature (usually in late June) four 1.8-m-long center rows were sampled from each plot for the following variables: number of ears nr2, height of plants (cm), grain protein, and grain and straw production (g nr 2 ), grain weight per ear (g) and weight of 1,000 grains (g). The tillering index (ears plant1) was calculated using the ratio of number of ears nr 2 at harvest to the plant density
BARLEY YIELD AND WEED DEVELOPMENT
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TABLE 2. Seed depth (cm) and plant density (plants m2) of barley under no-tillage and conventional tillage during the 3-year study period. 1992/93 Seed depth Plant density (plants/m2) (cm) No-tillage Conventional tillage LSD
2.72 b 4.14 a 0.40
360.6 a 270.9 b 13.1
1993/94 Seed depth Plant density (cm) (plants/m2) 1.32 b 3.78 a 0.55
355.5 a 268.1b 29.8
1994/95 Seed depth Plant density (cm) (plants/m2) 2.36 b 4.07 a 0.46
386.0 a 283.2 b 21.2
LSD=least significant difference at PO.025; numbers in a row followed by the same letter are not significantly different at P 10C)
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O, AND DEL MO
LSD=least significant difference at P
