Sugar beet (Beta vulgaris L.) response to diammonium phosphate and potassium sulphate under saline-sodic conditions

Salinity and sodicity are prime threats to land resources resulting in huge economic and associated social consequences in several countries. Nutrient deficiencies reduce crop productivity in salt-affected regions. Soil fertility has not been sustainably managed in salt-affected arid regions. Few researchers investigated the crop responses to phosphorus and potassium interactions especially in saline-sodic soils. A research study was carried out to explore the effect of diammonium phosphorus (DAP) and potassium sulphate (K2SO4) on sugar beet (Beta vulgaris L.) grown in a saline-sodic field located in Kohat district of Pakistan. The crop was irrigated with ground water with ECiw value of 2.17-3.0 dS/m. Three levels each of K2O (0, 75 and 150 kg/ha) as K2SO4 and P2O5 (0, 60 and 120 kg/ha) as DAP were applied. The application of P significantly affected fresh beet and shoot yield while K fertilizers had significant effect on fresh beet yield and ratio of beet: shoot, while non-significant effects on the fresh shoot were observed. The application of K-1 and K-2 promoted sugar beet shoot yield by 49.2 and 49.2% at P-1 and 64.4 and 59.7% at P-2, respectively over controls. In comparison with controls, fresh beet yield was increased (%) by 15 and 51, 45 and 84, and 50 and 58 for corresponding K1 and K-2 at P-0, P-1 and P-2, respectively. Addition of P1 and P2 increased beet yield by 37 and 47% over control. The shoot [P] (mmol/kg) were achieved as 55.2, 73.6 and 84.3 at P-0, P-1 and P-2, respectively. The shoot [Mg] and [SO4] tended to decrease with increasing P levels, while [SO4] was markedly reduced at P-2. The effect of P on leaf [Na] was non-significant, but increasing levels of K decreased [Na] substantially at P-0 and P-1, but there was no difference in the effect of K level on [Na] at P-2. Consequently, K application reduced leaf Na: K ratios. Fresh shoot yield was weakly associated with leaf [P] (R-2 = 0.53). The leaf Na: K ratio showed a negative relationship (R-2 = 0.90) with leaf [K]. A strongly positive relationship (R-2 = 0.75) was observed between leaf [K] and fresh beet yield. The addition of K2SO4 also enhanced [SO4] and SO4: P ratios in leaf tissues. The ratio of Na: K in the shoot decreased with increasing K application. These results demonstrated that interactions of K and P could mitigate the adverse effects of salinity and sodicity in soils. This would contribute to the efficient management of soil fertility system in arid-climate agriculture.