Physiological Response and Productivity of Alfalfa to Potassium Foliar and Soil Applications under Saline Calcareous Soil Conditions

Abstract

A field experiment was conducted at Nubaria Agricultural Research Station, El-Behira Government, Egypt along the duration of 2015 to 2017 to study the physiological response and productivity of alfalfa (cv., Nubaria1) to seven potassium fertilization treatment of 0, 28.6, 57.14Kg/ha as soil dressing, spraying with 1%K2O and 2% K2O alone or in combination with adding 28.6Kg K2O/ha under saline calcareous soil conditions. Experimental design was Randomized Complete Block design with four replications. Eighteen successive cuts were taken (Nine cuts /year), to estimate growth and physiological parameters, and alfalfa productivity. Potassium fertilization treatments had significant effects on all studied traits in individual cuts except the 1st and 9th cuts in the first year and 2nd cut in the second year for plant height, the 2nd and 7th cuts in the two years for dry matter%, the 2nd cut in the second year for dry forage Kg/m2 and 1st, 4th and 5th cuts for protein content in the first year. In general, plant height, leaf steam ratio, green forage yield Kg/m2, dry matter%, dry forage yield Kg/m2, relative water content, K+ content, K+/Na+ ratio and protein content increased significantly when plants received 28.6 K2O/ha + 2%K2O and 57Kg K2O/ ha with insignificant difference as compared with other potassium treatments. Also, a significant increase was recorded in Na+ content in leaves under control K+ treatment (0 K2O/ha). Linear relationship was found between potassium fertilization rates (soil dressing, foliar application as well as 28.6KgK2O/ha +foliar1 and 2% applications) and fresh forage weight t/ha. The linear regression equation showed that as potassium fertilizer rate (soil dressing) increased by one unite/ha, fresh forage weight/ha increased by 1.139t/ha and as potassium fertilizer rate (foliar application) increased by one unite/ha, fresh forage weight/ha increased by 3.112t/ha. In addition, the highest fresh forage weight/ha (125.850 t/ha) was produced under treatment of 28.6KgK2O/ha + 2%K2O. Highly positive significant correlation coefficients were found for all traits except the relation between Na+ content and other traits which was a highly significant negative relationship. Profitability assessment results revealed that addition of 28.6KgK2O/ha with foliar application of 2%K2O as potassin 30%K2O followed by addition of 57.14KgK2O/ha markedly obtained the highest values of alfalfa yield with insignificant difference. These results were incorporated with the highest values of output, net income and the investment ratio. Results indicated that controlling soil fertility, especially K+ as soil application, in addition to foliar application under saline calcareous soil condition is considered to be one of the most important factors to overcome the negative effects of salinity stress.