Reakcija bijele djeteline (Trifolium repens L.) na gnojidbu dušikom i pašno opterećenje u poluprirodnom travnjaku.

The response of white clover (Trifolium repens L.) to N fertilizing and stocking density in semi-natural grassland.

Reduction of stocking rates and fertilizer inputs are recommended for maintaining or enhancing biodiversity of semi-natural habitats. White clover population could be affected by changes in grassland production intensity. The aim of the present study was to investigate the white clover response on N application and stocking density. Three-year experiment was carried out on semi-natural grassland that was rotationally grazed with sheep. Three levels of N fertilizer were applied: 35, 100 and 150 kg N ha-1 (N35, N100 and N150, respectively) and two levels of stocking density were managed: 68 and 119 animal units ha-1 (ZP68 and ZP119, respectively) to investigate their effect on white clover dry matter (DM) yield, white clover content, frequency and regenerative ability. White clover DM yield and its content in the sward was not affected by the stocking density. The white clover content decreased during the experiment. The effect of N application on regenerative ability parameters was not constant and depends on the part of the vegetation season. These results indicate that the white clover is an unstable floristic component in the type of grassland investigated under applied management practice. However, reduction in N inputs is necessary to improve performance and the regenerative ability of the white clover. [ABSTRACT FROM AUTHOR]

Smanjenje pašnog opterećenja i primjena mineralnih gnojiva mjere su održanja ili povećanja bioraznolikosti poluprirodnih travnjaka. Promjene intenziteta proizvodnje mogu utjecati na populaciju bijele djeteline u sastavu pašnjaka. Cilj ovoga rada bio je utvrditi reakciju bijele djeteline u uvjetima primjene manjih količina dušika i smanjenja zaposjednutosti pregona. Trogodišnje istraživanje provedeno je na poluprirodnom travnjaku, u uvjetima rotacijskog napasivanja ovcama. Istraživan je utjecaj gnojidbe dušikom u količinama od 35 (N35), 100 (N100) i 150 (N150) kg N ha-1 i zaposjednutosti pregona od 68 (ZP68) uvjetnih grla (UG) i 119 UG ha-1 (ZP119) na prinos ST bijele djeteline i njezin udio u dostupnoj biljnoj masi, te učestalost i regenerativnu sposobnost bijele djeteline. Zaposjednutost pregona nije utjecala na prinos ST bijele djeteline niti na udio bijele djeteline u dostupnoj biljnoj masi. Gnojidba sa 35 kg N ha-1 povećala je prinos ST bijele djeteline uz povećanje relativnog udjela prosječno 34 % i 48 % u usporedbi sa 100 kg N ha-1 i 150 kg N ha-1 samo u jednoj godini istraživanja. Tijekom eksperimentalnog razdoblja utvrden je trend smanjenja broja vegetativnih vrhova, dužine vriježa i mase ST vriježa bijele djeteline. Reakcija bijele djeteline u pokazateljima regenerativne sposobnosti na zaposjednutost pregona i gnojidbu bila je različita, ovisno o dijelu vegetacijske sezone. Rezultati upućuju na to da je bijela djetelina nestabilna florna sastavnica ovakvog tipa pašnjaka. Unatoč tome, smanjenje primjene N poželjno je u cilju bolje regeneracijske sposobnosti i produktivnosti bijele djeteline. [ABSTRACT FROM AUTHOR]

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