Nitrogen Nutrition Diagnostics for Agricultural Crops in Lithuania

Abstract

We have validated the significance of mineral nitrogen present in the soil for diagnosing the agricultural crops need for fertilization as well as its effects on the environment. This was done by conducting the field and laboratory experiments under Lithuanian agro-climatic conditions. The yield of agricultural crops most resiliently correlated with mineral nitrogen, somewhat less with nitrate nitrogen and the least with ammonia nitrogen. Yield of grains correlated the best with nitrogen amount measured in spring in 0-60 cm soil layer. Following the mineral nitrogen concentration in soil, the soils in Lithuania can be grouped into five groups: I - less than 5 mg-kg"1 Nmjn in soil, very low; II - 5.1 - 10 mg-kg"1 Nmin in soil, low; rn -10.1 - 15 mg-kg"1 Nmin in soil, medium; IV- 15.1 -20 ing-kg^N,™, in soil, high; V- more than 20 mg-kg"1 N,™ in soil, very high. The crop yield and the efficacy of nitrogen fertilizer depends on the amount of the mineral nitrogen in soil. When it increases, the plant yield increases and the mineral fertilizers efficacy decreases. The crop should be fertilized additionally when total nitrogen in dry matter is less than 35 gkg"', N: P ratio less than 9.0, K: N ratio more than 0.90. Fertilization only with big rates of nitrogen increased the nitrates concentration in lysimeter water. This concentration was less, when nitrogen fertilization was applied on the background of phosphorus and potassium fertilization.