Total nitrogen concentration in leaves of potatoes (Solanum tuberosumL.) as an index of nutritional status

Abstract

SummaryLeaf samples were collected, at weekly intervals, throughout the growing season, from potato (Solanum tuberosumL.) plants supplied with varying amounts of nitrogen (0, 60, 120, 180 and 240 kg N/ha) and analysed for total N. Application of nitrogen increased the N concentration in the green leaves at all stages of growth. There was a significant curvilinear relationship between the final tuber yield and the total N concentration in the leaves at 48–90 days after planting in 1968–9 and at 79–107 days after planting in 1969–70. The N concentration at 70–90 days after planting was consistently related to the final tuber yield in both years. Thus this period was ideal for assessing the nitrogen status of potato plants. The critical concentration of total nitrogen generally decreased with advance in age. It ranged from 4·65% at 76 days to 3·30% at 90 days during 1968–9, whereas in 1969–70 it ranged from 4·20% at 79 days to 3·80% at 93 days. During the period from 83 to 86 days the critical percentage was around 3·6% in both the years.

Establishment of Continuous Critical Levels for Indices of Plant and Presidedress Soil Nitrogen Status in the Potato Crop

“…Although the critical level is theoretically a largely consensual concept, there are many ways to estimate it. On the basis of the relationships between N indicators and yield, different researchers use values corresponding to a yield reduction of either 5% [18] or 10% [19] as the critical level or even the point where the tangent drawn on the response curve has a unit slope (y/x ¼ 1). [20] Researchers who use the linear plateau model consider the point of interception between the straight line segments as critical level.…”

Establishment of Continuous Critical Levels for Indices of Plant and Presidedress Soil Nitrogen Status in the Potato Crop

“…On the basis of the relationships between N indicators and yield, different researchers use values corresponding to a yield reduction of either 5% [18] or 10% [19] as the critical level or even the point where the tangent drawn on the response curve has a unit slope (y/x ¼ 1). The concept of critical level presupposes the existence of a simple point on the curve that relates the level of the N indicator with the yield.…”

Effects of N rates and harvest dates on the efficiency of 15N-labelled fertilizer on early harvested potatoes (Solanum tuberosum L.)

“…Gupta and Saxena (1976) suggested using the toral N concentration in potato leaves as an index of nutritional status. Greenwood et al (1985) attempted to establish quantitative relationships among tuber yields and weights, N contents of foliage and tubers, and soil N measurements.…”