Impact of Rainfall Pattern on Native Arbuscular-Mycorrhizal Activity Influencing Phosphorus Utilization by Direct Seeded Rainfed Upland Rice (Oryza sativa L.)

Abstract

Efficacy of native arbuscular mycorrhiza to support phosphorus nutrition of rainfed upland rice was assessed under various rainfall patterns. Native arbuscular-mycorrhiza aided phosphorus acquisition by rainfed upland rice (Oryza sativa L.), over the period of 6 years (in alternate year’s between 1999 and 2009) having variable rainfall pattern, under rice mono-cropping and potential arbuscular-mycorrhiza-supportive rice based rotations were compared. Among these, the 2 years rotation of maize (Zea mays L.) relay cropped by horse gram (Dolichos biflorus L.) in the first year and followed by upland rice in the second year was most mycorrhiza-supportive. While phosphorus uptake in rice was positively correlated (r = 0.6301–0.7821) with the extent of mycorrhizal colonization under various crop rotations, the extent of influence of arbuscular-mycorrhizal colonization was greater in less rainfall year of 2009 (R 2 = 0.5450) than normal rainfall year of 2007 (R 2 = 0.3971). The mycorrhizal advantage to rice under most mycorrhiza supportive crop rotation (maize-horse gram-rice), in terms of mycorrhiza-aided phosphorus acquisition efficiency, on the other hand, was negatively correlated (r = −0.684 to −0.799) with the amount of rainfall received over a period under study (6 years), confirming higher mycorrhizal efficacy under moisture stress. The analysis emphasized the potential of exploiting native arbuscular mycorrhizal fungi as climate resilient agricultural technology component in rainfed ecology under the present climate change scenario leading to reducing moisture availability.