Nezāļu dinamikas pētījumi Latvijā aizsākti laika periodā no 1947. gada līdz 1982. gadam, kad ar šo jautājumu sāka nodarboties V.Gurskis, A.Rasiņš, M.Tauriņa u.c. toreizējā Vissavienības augu aizsardzības institūta darba ietvaros. Nezāļu ikgadējas uzskaites Latvijā Kurzemes - Zemgales novada 6 rajonu saimniecībās 1994. gadā uzsāka arī Latvijas lauksaimniecības universitātes laukkopības katedras pētnieki, kuru mērķis bija sniegt labību sējumu nezāļainības izmaiņu un to cēloņu analīzi Latvijas rietumu daļas saimniecībās pēdējo gadu laikā.<br /> <p><b>Pētījumu metodika</b><br /> Sējumu nezāļainības uzskaitei Latvijas lauksaimniecības universitātes laukkopības katedra no 1994. līdz 2001. gadam izmantoja A.Rasiņa un M.Tauriņas izstrādāto metodi, kura aprobēta iepriekšējos gados un sekmīgi izturējusi laika pārbaudi. Metodes teorētiskais pamatojums balstās uz lineāro sakarību ciešumu starp nezāļu sugas sastopamību atsevišķos lauka punktos un šīs pašas nezāles skaitu gabalos uz m². Nezāļu daudzums graudaugu sējumos noteikts jūlija mēnešos, novērtējot atsevišķu nezāļu sastopamību 200 cm² rāmītī, bet pēc tam ar tabulu palīdzību sastopamību novērtējot kā nezāļu sugu skaitu uz m². Šo sējumu nezāļainības uzskaites paņēmienu pirmais apraksta D.Brauns, nosaucot to par punktu - kvadrātu metodi, bet tālāk pilnveido un noformē plašākai lietošanai A.Rasiņš.<br /> Vienota nezāļu uzskaites metodika ļāva salīdzināt sējumu nezāļainību piecdesmit gadu ilgā periodā.</p> <b>Rezultāti</b><br /> Iegūtie nezāļu uzskaites rezultāti dažādos gados ļauj izdarīt secinājumus, ka uz pilnīgas iznīkšanas robežas atrodas tādas tīruma nezāļu sugas kā lauku kokālis <i>Agrostemma githago</i> un rudzu lāčauza <i>Bromus secalinus</i>, kuras 1947. gadā bija vienas no visbiežāk sastopamajām nezālēm. Salīdzinot ar 1947. gadu, labību agrocenozēs samazinās ķeraiņu madaras <i>Galium aparine</i> sastopamība, bet zilās rudzupuķes <i>Centaurea cyanus</i> izplatība deviņdesmitajos gados ir palielinājusies.<br /> <br /> <hr size="2" width="100%" /> <b>Dominējošo nezāļu saraksts ranžētā secībā pēc skaita labību agrofitocenozēs</b><br /> <br /> <i>Kurzeme - Zemgale<br /> <br /> </i> <table bordercolorlight="#C0C0C0" bordercolordark="#808080" border="2" bordercolor="#808080" cellpadding="0" cellspacing="0" width="85%"> <tbody> <tr> <td width="30%"> <p align="center"><font face="Times New Roman" size="2">Līdz 1947. gadam</font></p> </td> <td align="center" width="40%"> <p><font face="Times New Roman" size="2">1981. - 1982.g.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">1996.g.</font></p> </td> </tr> <tr> <td width="30%"> <p><font face="Times New Roman" size="2">1. <i>Viola</i> spp.</font></p> </td> <td width="40%"> <p><font face="Times New Roman" size="2">1. <i>Matricaria perforata</i> Merat.</font></p> </td> <td> <p><font face="Times New Roman" size="2">1. <i>Elytrygia repens</i> (L.) Nevski</font></p> </td> </tr> <tr> <td width="30%"> <p><font face="Times New Roman" size="2">2. <i>Cirsium arvense</i> (L) Csop.</font></p> </td> <td width="40%"> <p><font face="Times New Roman" size="2">2. <i>Viola</i> spp.</font></p> </td> <td> <p><font face="Times New Roman" size="2">2. <i>Matricaria perforata</i> Merat.</font></p> </td> </tr> <tr> <td width="30%"> <p><font face="Times New Roman" size="2">3. <i>Achillea millefolium</i> L.</font></p> </td> <td width="40%"> <p><font face="Times New Roman" size="2">3. <i>Taraxacum officinale</i> Web. agg.</font></p> </td> <td> <p><font face="Times New Roman" size="2">3. <i>Viola</i> spp.</font></p> </td> </tr> <tr> <td width="30%"> <p><font face="Times New Roman" size="2">4. <i>Bromus secalinus</i> L.</font></p> </td> <td width="40%"> <p><font face="Times New Roman" size="2">4. <i>Elytrygia repens</i> (L.) Nevski</font></p> </td> <td> <p><font face="Times New Roman" size="2">4. <i>Stellaria media</i> (L.) Vill.</font></p> </td> </tr> <tr> <td width="30%"> <p><font face="Times New Roman" size="2">5. <i>Galeopsis</i> spp.</font></p> </td> <td width="40%"> <p><font face="Times New Roman" size="2">5. <i>Fallopia convolvulus</i> (L.) A Love</font></p> </td> <td> <p><font face="Times New Roman" size="2">5. <i>Fallopia convolvulus</i> (L.) A Love</font></p> </td> </tr> <tr> <td width="30%"> <p><font face="Times New Roman" size="2">6. <i>Polygonum aviculare</i> L.</font></p> </td> <td width="40%"> <p><font face="Times New Roman" size="2">6. <i>Chenopodium spp., Galeopsis spp.</i></font></p> </td> <td> <p><font face="Times New Roman" size="2">6. <i>Cirsium arvense</i> (L.) Csop.</font></p> </td> </tr> <tr> <td width="30%"> <p><font face="Times New Roman" size="2">7. <i>Centaurea cyanus</i> L.</font></p> </td> <td width="40%"> <p><font face="Times New Roman" size="2">7. <i>Stellaria media</i> (L.) Vill.</font></p> </td> <td> <p><font face="Times New Roman" size="2">7. <i>Galium aparine</i> L.</font></p> </td> </tr> <tr> <td width="30%"> <p><font face="Times New Roman" size="2">8.<i>Myosotis</i> spp.</font></p> </td> <td width="40%"> <p><font face="Times New Roman" size="2">8. <i>Myosotis</i> spp.</font></p> </td> <td> <p><font face="Times New Roman" size="2">8. <i>Polygonum</i> spp.</font></p> </td> </tr> <tr> <td width="30%"> <p><font face="Times New Roman" size="2">9. <i>Elytrygia repens</i> (L.) Nevski</font></p> </td> <td width="40%"> <p><font face="Times New Roman" size="2">9. <i>Cirsium arvense</i> (L.) Csop.</font></p> </td> <td> <p><font face="Times New Roman" size="2">9. <i>Galeopsis spp., Veronica spp.</i></font></p> </td> </tr> <tr> <td width="30%"> <p><font face="Times New Roman" size="2">10. <i>Chenopodium spp.,<br /> &nbsp;Capsella bursa pastoris</i> (L.) Medik.</font></p> </td> <td width="40%"> <p><font face="Times New Roman" size="2">10. <i>Capsella bursa-pastoris</i> (L.) Medik.,&nbsp;<br /> <i>Polygonum spp.</i></font></p> </td> <td> <p><font face="Times New Roman" size="2">10. <i>Chenopodium spp</i>.</font></p> </td> </tr> </tbody> </table> Pēdējos piecdesmit gados ir pieaugusi šādu nezāļu sastopamība: <i>Veronica spp., Euphorbia helioscopia, Lapsana communis,</i> <i>Poa annua, Lamium purpureum, Stellaria media.</i> No daudzgadīgām nezālēm samazinājusies <i>Rumex acetosella</i> un <i>Achillea millefolium</i> sastopamība.<br /> Labību sējumos pēdējos gados ir pieaugusi <i>Ranunculus spp., Artemisia vulgaris, Mentha arvensis</i> un <i>Stachys palustris</i> nezāļu sastopamība. <i>Artemisia vulgaris</i> norāda uz zemkopības līmeņa pazemināšanos, bet <i>Mentha arvensis</i> un <i>Stachys</i> <i>palustris</i> L. ilustrē likumsakarīgas izmaiņas agrobiocenozes sastāvā, kam par pamatu ir tādu nezāļu savairošanās, kas ir izturīgas pret MCPA un glifosātu herbicīdiem. Tipisks piemērs cilvēku saimnieciskās darbības rezultātā un herbicīdu pielietošanā ir <i>Matricaria perforata (Tripleurospermum inodorum)</i> nezāļu skaita pieaugums sējumos. Pieaugot nezāļu rezistencei pret herbicīdiem, kā arī spējai vienā sezonā nogatavināt vairākas paaudzes sēklas, pēdējos gados pieaug <i>Stellaria</i> <i>media</i> sastopamība.<br /> Laikā no 1994. - 1998. gadam labību agrofitocenozēs dominējošā nezāle ir <i>Elytrygia repens.<br /> <br /> </i> <hr size="2" width="100%" /> <b>Nezāļu sugu izplatības ranžētā secībā izmaiņas labību sējumos</b><i><br /> </i> <font size="3"><b><br /> </b></font> <table bordercolorlight="#C0C0C0" bordercolordark="#808080" border="2" bordercolor="#808080" cellpadding="0" cellspacing="0" width="65%"> <tbody> <tr> <td> <p><i><font face="Times New Roman" size="2">Nezāļu sugas, to grupas</font></i></p> </td> <td> <p><i><font face="Times New Roman" size="2">Līdz 1947. gadam</font></i></p> </td> <td> <p><i><font face="Times New Roman" size="2">1981.-1982.g.</font></i></p> </td> <td> <p><i><font face="Times New Roman" size="2">1996.g.</font></i></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2">&nbsp; <b>Viengadīgās nezāles</b></font></p> </td> <td align="center"><br /> </td> <td align="center"><br /> </td> <td align="center"><br /> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Viola spp.</i></font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">1</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">2</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">4,7</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Bromus secalinus</i> L.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">4</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">-</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">-</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Galeopsis</i> spp.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">5</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">6,5</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">10,5</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Polygonum aviculare</i> L.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">7</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">10,5</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">8,5</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Centaurea cianus</i> L.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">8</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">12</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">22,3</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Myosotis</i> spp.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">9</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">8,5</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">17,0</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Capsella bursa-pastoris</i> (L.) Medik.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">11,5</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">10,5</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">18,7</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Chenopodium</i> spp.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">11,5</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">6,5</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">12,7</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Spergula arvensis</i> L.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">15</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Fallopia convolvulus</i> (L.) A. Love</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">17</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">5</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">6,8</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Polygonum scabrum</i> Moench.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">18</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">14,5</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">8,5</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Apera spica-venti</i> (L.) Beauv.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">22</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Agrostemma githago</i> L.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">24</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">-</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">-</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Stellaria media</i> (L.) Vill.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">25</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">7</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">5</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Lamium purpureum</i> L.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">29</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">12</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">11,6</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Matricaria perforata</i> Merat.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">1</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">4,3</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Galium aparine</i> L.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">7</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Veronica</i> spp.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">10,7</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Euphorbia helioscopia</i> L.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">15,7</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Lapsana communis</i> L.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">-</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Thlapsi arvense</i> L.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">18</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Poa annua</i> L.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">17,7</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Fumaria officinalis</i> L.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Matricaria discoidea</i> DC.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><b>Daudzgadīgās nezāles</b></font></p> </td> <td align="center"><br /> </td> <td align="center"><br /> </td> <td align="center"><br /> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Cirsium arvense</i> (L.) Csop.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">2</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">9</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">5,7</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Achillea millefolium</i> L.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">3</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">11</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Elytrygia repens</i> (L.) Nevski</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">11</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">4</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">3,3</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Rumex acetosella</i> L.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">14</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">14,5</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Sonchus arvensis</i> L.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">21</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">8,5</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">15</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Equisetum arvense</i> L.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">27</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">13,5</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">20</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Taraxacum officinale</i> Web. agg.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">3</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">20,7</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Tussilago farfara</i> L.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">13,5</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Artemisia vulgaris</i> L.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">26,7</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Ranunculus</i> spp.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">19,5</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Potentilla</i> spp.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Mentha arvensis</i> L.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> </tr> <tr> <td> <p><font face="Times New Roman" size="2"><i>Stachys palustris</i> L.</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> <td align="center"> <p><font face="Times New Roman" size="2">&gt;30</font></p> </td> </tr> </tbody> </table> Latvijas lauksaimniecībā deviņdesmitajos gados notiek pārmaiņas herbicīdu lietošanas apjomos. Herbicīdu lietošanas pieaugums, labību sējumu īpatsvara palielināšanās sējumu struktūrā un zemnieku saimniecību diferencēšanās ir par cēloni tam, ka piesārņotības pakāpe ar nezālēm bijusi mazāka. <p>Palielinoties herbicīdu lietošanas apjomiem, palielinās to labību sējumu skaits, kur <i>Elytrigia repens</i> vairs nav konstatēta un tādu sējumu īpatsvars 2000. gadā jau ir 27 % no kopējā lauku skaita. Vēl lielāks nezāļu skaita samazinājums ir <i>Cirsium spp</i>., kura 2000. gadā nav konstatēta 49 % no labību sējumiem. Palielinās to lauku skaits, kur nav konstatēta ne <i>Elytrigia repens</i> ne <i>Cirsium spp</i>. Tādu platību skaits 2000. gadā bija 17 % no kopējā labību sējumu skaita.<br /> <br /> </p> <hr size="2" width="100%" /> <b>Nezāļu sugu un ģints pārstāvju sastopamība vasarāju labības sējumos, % no lauku platības 2000. un 2001. gadā<br /> <br /> </b> <table bordercolorlight="#C0C0C0" bordercolordark="#808080" border="2" bordercolor="#808080" cellpadding="0" cellspacing="0" width="50%"> <tbody> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">N.p.<br /> k.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2">Sugas nosaukums</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">% no lauku<br /> &nbsp;platības</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">1.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Viola spp.</i></font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">76</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">2.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Fallopia convolvulus</i> (L.) A.Love</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">69</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">3.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Elytrigia repens</i> (L.) Nevski</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">63</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">4.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Galium aparine</i> L.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">62</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">5.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Lamium purpureum</i> L.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">60</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">6.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Stellaria media</i> (L.) Vill.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">53</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">7.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Cirsium spp.</i></font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">53</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">8.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Chenopodium</i> spp.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">47</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">9.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Matricatia perforata</i> Merat.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">41</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">10.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Euphorbia helioscopia</i> L.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">41</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">11.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Polygonum</i> spp.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">36</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">12.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Fumaria officinalis</i> L.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">28</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">13.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Taraxacum officinale</i> Web. agg.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">26</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">14.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Veronica</i> spp.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">25</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">15.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Myosotis</i> spp.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">21</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">16.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Thlaspi arvense</i> L.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">20</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">17.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Sonchus arvensis</i> L.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">19</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">18.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Equisetum arvense</i> L.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">15</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">19.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Stachys palustris</i> L.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">13</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">20.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Galeopsis</i> spp.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">12</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">21.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Achillea millefolium</i> L.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">11</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">22.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Lapsana communis</i> L.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">11</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">23.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Artemisia vulgaris</i> L.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">10</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">24.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Convolvulus arvensis</i> L.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">9</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">25.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Capsella bursa-pastoris</i> (L.) Medik.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">9</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">26.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Sinapis arvensis</i> L.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">9</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">27.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Lycopsis arvensis</i> L.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">9</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">28.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Anagalis arvensis</i> L.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">8</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">29.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Potentilla anserina</i> L.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">7</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">30.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Centaurea cyanus</i> L.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">7</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">31.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Tussilago farfara</i> L.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">6</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">32.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Mentha arvensis</i> L.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">4</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">33.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Spergula arvensis</i> L.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">2</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">34.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Melilotus</i> spp.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">2</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">35.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Rumex acetosella</i> L.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">2</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">36.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Stellaria graminea</i> L.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">2</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">37.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Vicia tetrasperma</i> (L.) Schreb.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">2</font></p> </td> </tr> <tr> <td align="center" width="33"> <p><font face="Times New Roman" size="2">38.</font></p> </td> <td width="209"> <p><font face="Times New Roman" size="2"><i>Galinsoga</i> spp.</font></p> </td> <td align="center" width="117"> <p><font face="Times New Roman" size="2">1</font></p> </td> </tr> </tbody> </table> <p><b>Literatūra</b><br /> <font size="2">D.Lapiņš, A.Bērziņš, J.Koroļova, A.Sprincina. Nezāļu skaita un sugu sastāva dinamika vasarāju labību sējumos Kurzemē un Zemgalē // Agronomijas vēstisNr.4.- Jelgava, LLU, 2002., 97. - 101. lpp.<br /> Latvijas Republikas nezāļu izplatība, botāniskais sastāvs, to dinamika un kaitīgums, nezāļainības ierobežošanas un apkarošanas pasākumu optimizācija. // Granta Nr. 93.729 atskaite.- Jelgava, LLU, 1997.- 143 lpp.<br /> </font></p> <p><font size="2"><br /> </font></p> <div align="right"> <font size="2">Sagatavoja:</font> <i>Latvijas Lauksaimniecības universitāte<br /> Laukkopības katedra</i><br /> <i>D. Lapiņš, D.Oboļeviča</i> </div> 2012-02-07T14:22:32Z tag:biodiv.lvgma.gov.lv,2012-02-07:/cooperation/lauksaimn/fol815176 http://biodiv.lvgma.gov.lv/misc_/CHM2/Site.gif Latvian Biodiversity Clearing-House Mehanism