ANÁLISIS DE RESOLUCIONES MUNICIPALES PERÍODO 2005-

Priekuli Plant Breeding Station, Priekuli, LV 4126, Cesis, Latvia, e-mail: livija@e-apollo

Abstract

In Priekuli Plant Breeding Station since 1958 on the basis of fertilizing background with stable manure 10 and 20 t ha-1 _{the influence of five crop rotations on yield and quality of}

cereals was studied. Since the beginning of experiments one of the main tasks was to find ways that promoted the health and vigour of the crop plants to provide profitable yields and quality, and to reduce weed pressure without pesticides use. Data obtained allowed conclusions regarding capability of main field crops in Latvia to provide weed suppression in a long-term period. Data shows that crop rotation had a considerable impact on yields and quality of cereals: barley, rye and wheat, and potato. The greater the differences between crops in a rotation sequence, the better yield quality was fixed.

Key words: crop rotations, field crops, yield quality

Introduction

The choice of crop rotation is fundamental to the success of sustainable organic system. The rotation, in particular the ratio of soil fertility building to fertility exploiting cropping phases has a major influence on the yield of cereals and other crops. Crop rotation offers the most effective, indirect method of minimizing pest, disease and weed problems and maintaining and enhancing soil structure and fertility (Jordan, 1992). When crops are rotated, yields are usually 10 to 15 % higher than when they grow in monoculture (Reganold et al., 1990). Although research efforts on ecological farming have started to become active in Latvia recently, farmers have always evaluated the role of qualitative seed material. Both for organic and conventional farming systems the basis for stable and high production of field crops is high quality seed material. Apart from good agronomic management of the crop, seed production differs from grain production on the following key issues: land requirement, isolation, rogueing, and prevention of contamination and limitations of generations. Another difference is that seed crops must meet specific quality standards determined by the national seed regulations. The technical, administrative and legislative control by the certification agency provides guidelines that have to be followed to produce good quality seed that meets the standards (3).

In organic agriculture, the level of yield in organic produced cereals is normally 20–30 % less than in conventional production (Nielsen, 1997), and it can often be a problem getting

enough seed of good quality. Organic farmers must use organic seed material if such seed are available. Only a few countries in the EU have an organic seed production able to supply the market for organic seed material. Also in Latvia there are no resources to guarantee necessary demand for the present. However there exist in the country possibilities based on special long- term experimental data to develop recommendations for organic seed producers in advance. This report presents information on the influence of crop rotations on yield and quality of the main cereal crops without using of pesticides in Vidzeme region.

Material and methods

The experiment is located in Priekuli (57o19'N, 25o20'E) on a sod-podzolic sandy loam soil with the following characteristics in the year of establishment (1958): organic matter content (Tyurin’s method) 2.1 %, soil pHKCl 5.8 to 6.1, available phosphorus (DL-method) 80-100

mg kg-1_{, available potassium (DL-method) 100-120 mg kg}-1_{. The mean temperatures varied}

from -6.2 0_{C in January to 16.7} 0_{C in July. The mean annual rainfall was 691 mm.}

The experiment included five different rotations:

o Barley - potato - barley or oat

o Barley – clover - rye – potato

o Barley - clover - barley - rye - barley – potato

o Barley - clover – potato

o Barley - clover - clover - rye - barley – potato.

The red clover was used in rotations, and was established as an under-sowing crop in barley. Fertilisation background - stable manure: from 1958 to 1980 - 10 t ha-1_{, from 1981 - 20 t ha}-1_.

The average content of plant nutrients in the farmyard manure was as follows: N-68, P-38, and K-58. No pesticides were used. The area of common trial plots was 5900 m2. In 1959, 22 t ha-1 _{of lime were given. Measurements of soil nutrient content and crops yields were}

performed every year. Plant available P was determined by Egner, H.-Riehm, H or DL method, where the soil was extracted by calcium lactate solution.

Results and discussion

Data show that during a more than 40-year period on a stable manure background of 20 t ha-1

and without pesticides use in the vegetation period high cereal yields were not obtained in Vidzeme region (Table 1). Extra low yields were obtained in 2002 for the barley variety ‘Idumeja’ when crops suffered from hard frosts a month after sowing and severe attack of aphids in June. Nevertheless, the yield was in fact higher than expected. At the same time there were observed sharp differences in 1000-kernel weight recorded between variants that point on the marked influence of crop rotation. In all cases for barley the preference of crop rotations with inclusion of clover were found and positive effect of largest crop sequence fixed.

Table 1 The influence of crop rotation on yield and quality of cereals

Designations: * B - barley, P - potato, R - rye, C/g - clover/grass, W- wheat.

** Not included in crop rotation. ***Not grown in the corresponding year. Crop rotation

Yield and quality _{B- P-B B- C/g-P} B- C/g- B- R- B-P B- C/g- C/g- R- B- P B– C/g- R- P Barley Yield, t ha-1 ‘Balga’, 2000 ‘Balga’, 1999 Barley 10th rotation ‘Idumeja’, 2002 (RS0.05 = 0.14-0.16) 2.0 1.8 1.6 1.3 *** 2.7 2.5 1.4 2.7 *** *** 1.3 2.9 *** *** 1.3 *** *** 2.9 1.3 1000 kernel weight, g ‘Balga’, 2000 ‘Balga’, 1999 Barley, 10th rotation ‘Idumeja’, 2002 36.2 34.7 35.2 42.8 *** 36.9 36.5 45.7 35.4 *** *** 47.3 37.9 *** *** 47.0 *** *** 36.9 46.4 Rye ‘Priekulu’ (3 rotations on average)

Yield, t ha-1 (RS0.05 = 0.38) ** ** 3.8 3.7 *** 1000 kernel weight, g ** ** 40.9 42.5 *** Wheat ‘Mironovskaja- 808’, 1999 Yield, t ha-1 (RS0.05 =0.14) ** ** 3.10 3.11 ** 1000 kernel weight, g ** ** 39.4 42.0 **

Winter rye is the most competitive field crop and is effective in controlling weeds. Rye growth and competitive ability suppresses weeds and reduces seed production by annual weeds and root growth of perennial weeds (Zarina, 2005). There were no fixed yield differences in both six-field crop rotations in 3 rotations on average, whereas 1000 kernel weight was highest in crop rotation with inclusion of two fields of clover/grass mixture. A study in Priekuli indicated that fertilizer background 20 t ha-1 of stable manure applied for winter wheat was too low to obtain economically based yield level. Similar situation was observed in rye and in winter wheat 1000 kernel weight was higher in crop rotation with two-fields clover/grass mixture.

Also potato yield formation and quality was sharply affected by crop rotation (Zarina, 1999; Zarina et al., 1999). The highest amount of tuber fraction 45-55 mm (recommended for seed material) was recorded in both six-field crop rotations.

0 20 40 60 80 < 45 mm 45-55 mm > 55 mm % b-p-b b-c-p b-c-b-r-b b-c-c-r-b

Fig. 1. The influence of crop rotation on structure of potato yield

The significance of inclusion of clover in one or two fields was not found. Significantly lower amount of potato seed fraction was recorded in both three-field crop rotations. Besides, there was found high significance of inclusion of clover-grass mixture in crop rotation that show that crop rotation was a major component of all sustainable farming systems. As indicated by crop rotations, different in the proportion of soil fertility building crop (grass/clover) in the rotation was one of the main tasks of investigations, long- term results approved it.

Conclusions

Selection of suitable crop rotation provided output of good quality yield on a base of low input fertilisation and without use of pesticides therefore crop rotation could be considered the key to sound organic farming practice, including organic seed production.

References

Jordan, V.W.L. (1992) Opportunities and constraints for integrated farming systems. Proc. 2nd European Society of Agronomy congress, Warwick University.

Nielsen, B.J. & Scheel, C.S. (1997) Production of quality cereal seed in Denmark. Proceedings of ECO-PB 1st International symposium on organic seed production and plant breeding, Berlin, Germany November 2002. E.T. Lammerts van Bueren and K-P. Wilbois (eds). pp. 28-31.

Reganold, J.P., R.I. Papendick and J.F. Parr. (1990) Sustainable agriculture. Scientific American June 1990: pp. 112-120.

Zariņa L., Miķelsons V. (1999) Augsekas ietekme uz kartupeļu ražas kvalitāti. Agronomijas vēstis(Proceedings in Agronomy), Nr. 1, 1999., 107-108. lpp. In Latvian.

Zarina, L. (1999) Influence of previous crops on potato yields quality. Abstracts of 14th Triennial Conference of EAPR’99, Sorrento, May, 2-7, 1999, pp. 152-153.

Zarina L. (2005) Manifestation of allelopathy by influence of crop rotation. Programme and Abstracts. Workshop on Beneficial Interactions below Ground. Les Geneveys-sur-Cofrane. http://www.organicagcentre.ca/ResearchDatabase/