Overvintringsskader, kvantitativ eller kvalitativ process?

H÷fundur┌tgefandi┌tgßfußr┌tgßfusta­ur
RÝkhar­ BrynjˇlfssonB˙na­arfÚlag ═slands, BŠndaskˇlinn ß Hvanneyri, Rannsˇknastofnun landb˙na­arins, Rannsˇknast÷­ SkˇgrŠktar rÝkisins, Tilraunast÷­ hßskˇlans Ý meinafrŠ­i, Vei­imßlastofnun1989ReykjavÝk
Rit┴rgangurT÷lubla­Bls.
B˙vÝsindi235-40

gr-buv2-rb.PDF

Frß vefstjˇra: Greinina Ý heild sinni er a­ finna Ý pdf-skjalinu hÚr a­ ofan

ABSTRACT

Winter damage - quantitative or qualitative process?

Winter damage is usually considered as a qualitative process, i.e. the life or death of individual plants. The farmer, on the other hand, is more concerned with obtaining sufficient yields from his overwintering crops. Winter damage in perennials and winter annuals can materialize as one of the following:
    1. The number of surviving plants is not sufficient and they are not suitably distributed over the area to be able to make maximum use of the available resources for growth during the following summer.

    2. The surviving plants, regardless of number, are not sufficiently vigorous to be able to make maximum use of the available resources for growth.

    3. Weeds get the chance to outcompete the crop plants in the spring due to their limited number or their lack of vigour.

The majority of grass tillers disappears during winter, even under low stress. Due to the high density of tillers in the autumns, however, thinning of the stand is not detrimental, provided that the surviving tillers are evenly distributed. Various climatic and management factors can increase the mortality rate. Total mortality over a sufficiently large area is considered as winter kill (see 1). Reduced vigour caused by the same factors (see 2 and 3) is not treated as winter kill in the same sense.
Under normal farming conditions cases (2) and (3) are much more frequent than (1) and actually occur every year. An environmental factor, which causes winter kill every tenth year, will certainly lead to yield losses or a thinning of the tiller stand every year. It is therefore necessary to study the quantitative effects of climate and farming practices on winter hardiness rather than on winter kill per se.

Key words: winter damages.

YFIRLIT

Kal, kvantitatÝfur e­a kvalitatÝfur ferill?

═ umrŠ­um um kal er alla jafna liti­ ß fyrirbrig­i­ sem eigindlegan (kvalitatÝfan) feril, ■.e.a.s. um lÝf e­a dau­a plantna. Mßli­ er ■ˇ mun flˇknara en svo. Bˇndann sem lifir ß uppskeru t˙ns e­a akurs skiptir mestu hvort uppskerumagn er vi­unandi.

Ůetta rŠ­st af m÷rgu, en um fj÷lŠrar e­a vetrareinŠrar pl÷ntur skiptir eftirtali­ sÚrstaklega mßli:

    1. Hvort eftirlifandi pl÷ntur eru nŠgilega margar og hŠfilega dreif­ar um fl÷tinn til a­ fullnřta vaxtarskilyr­i komandi sumars.

    2. Hvort ■essar pl÷ntur, margar e­a fßar, eru svo kr÷ftugar a­ vori a­ ■Šr megni a­ fullnřta vaxtarskilyr­in.

    3. Hvort a­rar pl÷ntur en ■Šr sem sˇst er eftir (illgresi) nßi a­ kŠfa v÷xt nytjaplantnanna a­ vori vegna lÝtils fj÷lda ■eirra og/e­a lÝtils lÝfs■rˇttar.

Mj÷g mikill hluti sprota Ý t˙ni drepst yfir veturinn, jafnvel ■ˇ ßlag sÚ hˇflegt. Fj÷ldi a­ hausti er hins vegar svo mikill, a­ veruleg grisjun sem slÝk kemur ekki a­ s÷k sÚ dreifing eftirlifandi sprota nokkurn vegin j÷fn. Ţmsir ■Šttir ve­urfars og me­fer­ar valda ■vÝ a­ hlutfall dau­ra sprota hŠkkar. Nßi ■a­ 100% ß nŠgilega stˇrum blettum er tala­ um kal (sbr. 1. ■ßtt). Veiklun vegna s÷mu me­fer­ar (sbr. 2. og 3. ■ßtt) er hins vegar ekki talin til kals Ý venjulegum skilningi.

═ almennum b˙skap kemur 2. og 3. ■ßttur mun oftar fyrir en 1. ■ßttur og raunar alltaf. Me­fer­ar■ßttur sem veldur kali tÝunda hvert ßr mun ßrei­anlega valda uppskerutapi e­a grisjun nytjaplantna ÷ll ßr. ŮvÝ er ekki sÝ­ur mikilvŠgt a­ beina rannsˇknum a­ kvantitatÝfum aflei­ingum ve­urfars e­a b˙skaparhßtta ß vetrar■ol en kali Ý venjulegum skilningi.