Soil fertility and nutrient uptake by arecanut (Areca catechu L.) as affected by level and frequency of fertigation in a laterite soil

Changes in soil fertility status were evaluated for 10 years, from 1996 to 2006 to examine the impact of drip fertigation in a laterite soil and to determine the nutrient uptake pattern of arecanut (Areca catechu L.). Four fertigation levels (25%, 50%, 75% and 100% of recommended fertilizer dose, 100:18:117gN:P:Kpalm⁻¹ year⁻¹), three frequencies of fertigation (10, 20 and 30 days) and two controls (control 1: drip irrigation without fertilizer application and control 2: drip irrigation with 100% NPK soil application) were studied. The soil pH increased to 6.0 at the end of experiment in 2006 compared to the pre-experimental soil pH of 5.6 in 1996. In 0-25-cm depth interval, the soil organic carbon (SOC) increased significantly from 1.06% in 1999 to 1.84% in 2006, and in 25-50-cm depth interval, it increased from 0.68% to 1.13%. Temporal variation in available P and K content in arecanut root zone was significant due to drip fertigation. Pooled analysis of data, from 2000 to 2005, revealed significant impact of level and frequency of fertigation and their interaction on available P and K content. At 0-25-cm depth interval, increase in fertigation dose from 50% to 100% NPK did not result in significant increase of Bray's P content, which remained at par ranging from 5.24 to 5.32mgkg⁻¹. Fertigation every 30 days resulted in significantly higher available P (5.32mgkg⁻¹) than fertigation every 10 days (4.49mgkg⁻¹), while it was at par with fertigation every 20 days (5.09mgkg⁻¹). The K availability at 0-25-cm depth interval was significantly lower at 25% NPK level (114mgkg⁻¹) than at 75% (139mgkg⁻¹) and 100% (137mgkg⁻¹). With respect to fertigation frequency, the 30-day interval resulted in higher available K of 139mgkg⁻¹ than 20-day (128mgkg⁻¹) and 10-day intervals (120mgkg⁻¹). Availability of P and K at 25-50-cm depth interval followed similar trend as that of 0-25-cm depth interval. The total N uptake (gpalm⁻¹ year⁻¹) by leaves, nuts and husk varied between 143 in 0% NPK to 198 in 75% NPK fertigation level. Similarly, the total P uptake (gpalm⁻¹ year⁻¹) ranged between 15 for the 0% NPK and 25 for the 75% NPK treatment. The total K uptake (gpalm⁻¹ year⁻¹) was 62 for the 75% NPK treatment followed by 56 for the 25%, 56 for the 50%, 54 for the 100% and 46 for the 0% NPK treatments. The nutrient uptake pattern and marginal availability of soil P and K highlight the importance of drip fertigation during post-monsoon season to improve and sustain the yield of arecanut in a laterite soil.