INFLUENCE OF DIFFERENT MANAGING OF PERENNIAL GRASSES ON NO3-N CONCENTRATIONS IN LYZIMETRICS WATERS

INFLUENCE OF DIFFERENT MANAGING OF PERENNIAL GRASSES ON NO3-N CONCENTRATIONS IN LYZIMETRICS WATERS

VLIV ODLIŠNÉHO OBHOSPODAŘOVÁNÍ VÍCELETÝCH PÍCNIN NA KONCENTRACE NO3-N V LYZIMETRICKÝCH VODÁCH

J. Truneček, J. Šantrůček, M. Svobodová

Czech University of Agriculture in Prague, Faculty of Agronomy, Department of Forage Crops, Prague, Czech Republic

Summary

A plot field trial (1 plot 3x10m) was established in the year 1996 on the experimental field of the Czech University of Agriculture in Prague. The stands were harvested by 4 ways: 3 times cut with the mass removing, 1 times cut in the end of the vegetation period with the mass removing, 2 or 1 times mulched. Stationary field lysimetres for measuring of nutrients leaching were installed in the depth 0,5 m under undamaged soil profile on each variant. Lyzimetric waters were taken in 2 terms - at the beginning (March - April) and at the end (October - November) of vegetation period. Twice mulched stand shows by 35,84% bigger leaching of NO3 -N than the once mulched one. There is no difference in nitrates leaching between once and three times cut stands.

grasses, legumes, lysimetric waters, concentration of nitrate nitrogen

Souhrn

Polní pokus (1 parcela 3x10 m) byl založen v roce 1996 na pokusném pozemku České zemědělské univerzity v Praze. Porosty byly sklízeny 3 sečně s odvozem hmoty, 1 sečně na konci vegetace s odvozem hmoty, 2x nebo 1x (na konci vegetace) mulčovány. Polní lyzimetry pro sledování vyplavování nitrátů na jednotlivých variantách byly instalovány do hloubky 0,5 m pod neporušeným půdním profilem. Lyzimetrické vody byly odebírány na počátku (březen - duben) na konci vegetačního období (říjen - listopad). Dvakrát ročně mulčované porosty vykazovaly o 35,84% vyšší proplavování NO3 -N než jednou ročně mulčované. Mezi porosty 1x nebo 3x sečenými s odvozem hmoty nebyl ve vyplavování nitrátů rozdíl.

trávy, jeteloviny, lyzimetrické vody, koncentrace nitrátového dusíku

Introduction

One of the weighty problems of quality of surface and ground water is contamination with nitrate stuffs. Contents of nitrates in the sources for public supplies increased from 15 - 30 mg.l-1 in the year 1966 to approximately 20 - 65 mg.l-1in the 1989. The rations of nitrogen fertilizers significantly decreased after the year 1989 and it had influence on decreasing of nitrates content in the term 1989 - 1993. This trend in the decreasing of nitrates concentrations, however, does not continue after the year 1993 (SKOŘEPOVÁ, 1998). Restrictions of nitrates spreading prescribes the directive of Advice 91/676/ European economy partnership for members countries of EU (ROSENDORF, OŠLEJŠKOVÁ, PRCHALOVÁ,1998). The Czech government ratified the Intention of Law about Waters in the March 1999. The document is based on the demand for incorporating of EU laws in the sphere of water policy to our juridical system (JOKLOVÁ, 1999).

Nitrates leaching under legumes stands, comparing with other crops on arable land, depends on their ability to use the air nitrogen, on their perennial character and on deep roots of some species. Considering that legumes take only a part of the total used nitrogen quantity from soil solution, leaching under their stands is more intensive than for example under grasses or clover - grass mixtures. It was proved for example by SINCLAIR et al. (1992). Leaching of nitrates under clover - grass mixtures is directly proportional to the share of legumes. WATSON et al (1990) found out that leaching from clover - grass mixtures is bigger than leaching from grasses which are fertilized with nitrogen in amount corresponding to fixed nitrogen. GERTH (1989), BENKE et al.(1992) show similar results.

Methods

A plot field trial (1 plot 3x10m) was established in the year 1996 on the experimental field of the Czech University of Agriculture in Prague on chernozem, 281 m above the sea level. Bromus catharicus Tacit (50 kg.ha-1), Arrhenatherum elatius Median (50 kg.ha-1), Festuca pratensis Otava (30 kg.ha-1), Dactylis aschersoniana Tosca (18 kg.ha-1), Trifolium repens Huja (15 kg.ha-1), Medicago lupulina Alice (20 kg.ha-1), Lotus corniculatus Lotar (15 kg.ha-1) and Medicago media Mediana (18 kg.ha-1) were sown in the spring (row space 125 mm). Stands of Coronilla varia Eroza (16 kg.ha-1) and mixtures of Bromus catharicus + Coronilla varia (20+10 kg.ha-1), Dactylis aschersoniana + Trifolium repens (15+6 kg.ha-1), Festuca pratensis + Lotus corniculatus (20+6 kg.ha-1) a Arrhenatherum elatius + Medicago lupulina (20+10 kg.ha-1) of the same varieties were established in the year 1997. A part of the field was left without a forage stand (fellow). The stands were harvested by 4 ways: 3 times cut with the mass removing, 1 times cut in the end of the vegetation period with the mass removing, 2 or 1 times mulched by the mulcher AS 27/2 Enduro (BRD). Stationary field lysimetres for measuring of nutrients leaching were installed in the depth 0,5 m under undamaged soil profile on each variant. Lyzimetric waters were taken and analyzed in two terms (March - April and October - November). Values of leached nitrate nitrogen were compared with the Czech standard for drinking water (ČSN 75 7111).

Results and discussion

The results are presented in the table 1. It arises from the table 1, that the concentrations of leached nitrates under grasses, legumes and their mixtures are different, the biggest losses are under legumes. Several authors present the same trend (GUSTAFSON et al., 1992; SINCLAIR et al., 1992). The prescribed concentration for drinking water according to CSN 75 7111 11,3 mg NO3-N.l-1 was exceeded only in several cases under legumes (Trifolium repens, Medicago media, Medicago lupulina) and under mixtures (Coronilla varia + Bromus catharicus, Lothus corniculatus + Festuca pratensis). The prescribed concentrations under grasses were exceeded only under Bromus catharicus . The results of this experiment correspond with the data of

KOPEC (1992), when the lowest leaching of NO3 -N is under grasses stands. The influence of treatment frequency on NO3-N leaching intensity under cut variants has not been proved until now. This is presented by SINCLAIR at al. (1992), too. Differences between mulched variants are apparent from the table 1, when the twice mulched stand shows by 35,84% bigger leaching of NO3 -N than the once mulched one. It is in relation with faster exchanges of root mass in the soil and more intensive microbial activity. There is no difference in nitrates leaching between once and three times cut stands.

References are at authors disposal.

Kontaktní adresa: Ing. Jan Truneček; ČZU Praha, katedra pícninářství; 165 21 Praha 6 - Suchdol