UREA AND MANURE EFFECT ON GROWTH AND MINERAL CONTENTS OF MAIZE UNDER SALINE CONDITIONS

Abstract

Salinity and soil nutrient deficiencies are the main factors reducing plant productivity in arid and semiarid areas. Among the essential elements, nitrogen is usually the most growth limiting plant nutrient in saline or non-saline soils. A pot experiment was carried out in the greenhouse to evaluate the influence of composted manure and urea as nitrogen sources on growth and mineral [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sodium (Na)] content of maize (Zea mays L.) under different levels of salinity. Saline soils were prepared from an infertile loamy-sand soil, namely masatsuchi, by adding a mixture of Ca, Mg, and Na salt solutions with concentrations of 60, 110, and 160 mmol_c L⁻¹. The final salinity levels (ECe) achieved were 4, 9, and 13 dSm⁻¹ denoted as S1, S2, S3, respectively; S0 denotes untreated soil. The pH of the saline soils ranged from 7.1 to 7.4. Nitrogen was applied at four levels as follows: urea, composted manure, ½ urea + ½ composted manure, and a control (no N fertilizer). Each of the three levels of applied N was at the rate of 200 kg ha⁻¹. A basal dose of P and K was also applied. Treatments were factorially combined using RCB design with 3 replications. Maize was grown as the test crop. Plant growth and shoot and root biomass were monitored for 8 weeks, and shoot samples were also analyzed for N, P, K, Ca, Mg, and Na. Maize height and dry matter production were depressed with increasing salinity levels. The application of composted manure and urea fertilizer enhanced plant growth and nutrient uptake compared with the non-treated control. Maize growth was better under urea fertilizer than under composted manure. The uptake of nutrient was also affected by the salinity and form of fertilizer applied. Calcium, Mg, and Na uptake of shoot increased with increasing level of salinity irrespective of fertilizer level. However, for any level of salinity, the uptake of these elements differed in the following order: urea > urea + manure > composted manure > control. Nitrogen uptake decreased with increasing salinity up to S2 while P and K decreased up to S3. Irrespective of salinity, N, P, and K uptake were higher in urea and urea + manure treatments as compared to manure and control. The poor response of composted manure may be due to its short-term application or impeded N mineralization under saline conditions.

Acknowledgments