Long range effect of continuous rice wheat cropping under varying levels of N, P and K on yield and fertility status of soil with particular reference to iron

Abstract

A long term field experiment was conducted at the Institute of Agricultural Sciences, BHU, Varanasi, India to study the effect of NPK fertilizer on the stability of yield of rice and wheat grown in sequence and the fertility status of the soil. The yield of the two crops was maintained at low levels in fertilizer control plots, whereas in plots receiving high levels of fertilizers, rice yield showed declining trend over the years. Soil analysis of DTPA extractable Fe, Cu and Zn showed that high rates of NPK fertilizer had a declining effect on the content of these micro‐nutrients particularly Fe. The availability of Fe is further reduced under aerobic soil conditions. Thus, raising high yielding crops with high fertilizer doses may create micro‐nutrient deficiency condition which may be responsible for decline in rice yield. The interrelationship of Fe with other nutrients need to be studied for maintenance of soil fertility in long run.

Key words:

• Soil fertility
• Iron nutrition