The contribution of indigenous arbuscular mycorrhiza (AM) on phosphorus (P) uptake by groundnut was examined in a low P field soil. The fungicide benomyl was applied to eradicate mycorrhizal ...infection. The treatments consisted of three P levels viz. 0, 50 and 400 mg P kg-1 soil, with and without benomyl application. Groundnut as test crop was sown two weeks after the application of benomyl and was harvested four times covering the whole growth period. At each harvest, the shoot yield, shoot P concentration, root length, soil solution P (CLi) and per cent root infection by AM was determined for benomyl treated and untreated soil at all P levels. Benomyl showed no effect on soil solution P concentration. When P was limiting, application of benomyl did reduce early groundnut growth by 40-50% at P-0, and by 25-30% at P-50. At high P supply (P-400), benomyl had little or no effect on dry matter production. Thus, indicate that the effect of benomyl on plant growth was by its influence on P uptake from soil. Phosphorus supply affected percentage of root infected by AM which was 40% of the roots at P-0, and decreased to around 30% and 10% at P-50 and P-400. In the early growing season, the P influx of maize was dependent on P in soil solution and the effect of AM was rather large. At high P supply, the contribution of AM to P influx showed a decrease. Without or low AM infection and at low P level, the P influx was 62% of that with AM. During early growth period groundnut showed a similar behaviour as maize at middle growth stage and without AM reduction of P influx, which was to an extent of 67%. In absolute terms AM is more important at maximum growth in the early growth season for groundnut. It is evident from the present investigation that AM may make an significant contribution by about 35% to the P nutrition of groundnut, but other factors, like P solubilization by root exudates, may be even more important.
Proučevan je bil vpliv samonikle arbuskularna mikorize (AM) na sprejem fosforja (P) pri rastlinah arašida. Fungicid benomyl je bil uporabljen za zagotovitev kontrolnih rastlin brez mikorize. Gnojenje s P je potekalo na treh nivojih in sicer 0, 50 in 400 mg P na kg tal, z oziroma brez uporabe benomyla. Arašidi so bili posajeni dva tedna po tretiranju tal s fungicidom, vzorce so jemali štirikrat tekom obdobja rasti. Pri vsakem jemanju vzorcev je bila določena teža poganjkov, koncentracija P v poganjkih, dolžina korenin, topen P v tleh in odstotek okužbe z mikorizno glivo, na obeh nivojih tretiranja s fungicidom in na vseh nivojih dodatka P. Fungicid ni vplival na vsebnost topnega P v tleh. Ko je bil P omejujoč dejavnik je fungicid zmanjšal zgodnjo rast arašidov za 40 do 50% pri P-0 in za 25 do 30% pri P-50. Pri visokem dodatku P (P-400) je imel fungicid majhen vpliv ali sploh ni imel vpliva na pridelek sušine. Tako kaže, da je fungicid vplival na rast rastlin z vplivom na sprejem P iz tal. Oskrba s P je vplivala na AM, ki je bila 40% pri koreninah skupine rastlin P-0 in se je znižala na okoli 30% in 10% pri P-50 in P-400. Pri visokih odmerkih P se je zmanjšal pomen AM za oskrbo rastlin s P. Brez AM in pri nizkem nivoju P je bil dotok P v rastline samo 62% tistega, ki je bil pri rastlinah z AM. AM je najpomembnejša za zagotovitev maksimalne rasti v začetku rastne sezone arašidov. Raziskava je pokazala da je AM značilno prispevala z okoli 35% deležem oskrbe rastlin arašidov s P, da pa so lahko celo bolj pomembni tudi drugi vplivi, kot na primer, da izločki korenin prispevajo k povečanju topnega P v tleh.
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