Effect of composting on the extractability of plant nutrients in organic wastes is essential for their recycling in sustainable soil fertility management. Therefore, an experiment was carried out to determine the concentrations of total C, total N, extractable P, K, Na and B in five types of fresh and composted manures (namely buffalo, camel, cow, goat and poultry). Laboratory results showed that the extractability of elements varied considerably with the type of composted manure. Total C varied in the order cow > goat > buffalo > poultry > camel while total N was in the order buffalo > poultry > cow > camel > goat. Total C, total N, extractable K and Na decreased with composting, whereas extractable P and B increased. Goat manure had higher pH and EC values than cow and poultry manures whether in fresh or composted samples. A marked increase in the EC value was observed in composted manures, whereas pH was reduced with composting.

Salinity-fertility interaction has not been properly explored especially in saline-sodic soils. Therefore, the current study investigated the response of wheat (Triticum aestivum L.) to saline irrigation water in salinesodic soil supplemented with potassium (K) and phosphorus (P). Wheat was grown in pots filled with salinesodic soil which were irrigated either with normal or saline water. Potassium and P fertilizers were applied at two levels. Results indicated that growth of wheat plants was impaired by saline irrigation resulting in a decreased grain and dry matter yield. The P application had significant effect on the dry matter yield and other yield components. Potassium application significantly increased dry matter yield and root mass. Wheat yield increased by 14 and 7% with the application of 150 kg K 2 O ha -1 and 120 kg P 2 O 5 ha -1 over the control soil under saline irrigation. The higher yield was obtained with combined P and K treatment under non-saline irrigation. The P addition significantly affected shoot and root [P] and [Na], [K] and [Mg] in the shoot tissue while the K:Na ratio produced non-significant effects under both irrigation waters. The addition of K significantly affected [Na], [K] and K:Na ratio in shoot. All other root parameters were significantly affected by the K addition. The Ca uptake by roots increased with saline irrigation. The P addition increased [P] in plant tissue. The Na uptake by root and shoot tissues was depressed with the addition of P and K fertilizers. The higher K uptake increased K:Na ratio in both shoot and root tissues. The values of EC, SAR and [P], [Na], [Ca], [Mg], [Cl] and ratios of Na:K, Ca:P, Cl:P and SO 4 :P in the soil leachates significantly increased with saline irrigation. The P addition had significant bearing on the soil pH, SAR, [P] Effect of saline irrigation water on the leachability of salts, growth and chemical composition that the addition of P and K under saline-sodic conditions may affect salts and nutrients dynamics of the soil and was useful for crop productivity.

Potassium (K) and sodium (Na) coexist on the soil exchange complex and soil solution. Both cations may exert antagonistic or synergistic effects on mutual absorption and translocation within plants, particularly under saline and saline-sodic field conditions. This study investigated the role of K in alleviating the adverse effects of Na on wheat [Triticum aestivum (L), Iquilab-91] grown at two fields sites varying in salinity. The soils were moderately calcareous, weakly structured, mixed hyperthermic Typic Haplustepts. Site 1 was silty clay loam saline-sodic soil (ECe = 4.23-9.45 dS m . Both sites were treated with 0, 50 and 100 kg K ha -1 applied as K 2 SO 4 (41% K) fertilizer. Significant increases of 14 and 30% in grain yield were measured at both sites, and 35 and 54% increase in dry matter yields were observed in clay loam soil with the application of 50 and 100 kg K ha -1 . Potassium application decreased leaf [Na] and significantly increased [K]; the K:Na ratio showed a positive correlation with yield. Soil analysis showed significant increases in [K], [Na] and SAR, while pH, ECe and [Ca+Mg] were not affected by the K fertilizer. The K 2 SO 4 increased crop yield by mitigating the adverse effect of Na and would thus be an effective source of K for crop production in saline and saline-sodic soils.

No abstract

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 (K 2 SO 4 ) 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 EC iw value of 2.17-3.0 dS/ m. Three levels each of K 2 O (0, 75 and 150 kg/ha) as K 2 SO 4 and P 2 O 5 (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 K 1 and K 2 at P 0 , P 1 and P 2 , respectively. Addition of P 1 and P 2 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 [SO 4 ] tended to decrease with increasing P levels, while [SO 4 ] 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 K 2 SO 4 also enhanced [SO 4 ] and SO 4 :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.