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High salinity in soil can prevent root growth of most plants. To investigate soil salinity dynamics under drip irrigation with mulch film (DI) and its effects on cotton root length, we conducted field experiments in saline soil based on a monolith method using flooding irrigation with mulch film (FI) as a control at the Korla Experimental Station of the Xinjiang Academy of Agricultural Sciences, China in 2009 and 2010. The results showed that the total root length decreased 120 days after sowing (DAS) under DI, and was mainly centered in the 0–30 cm soil layer and at distances of 30–70 cm from the drip-lines. There was almost complete overlap in the area of root length decline and salt accumulation. In the soil depth of 0–30 cm and at distances of 30–70 cm from the drip-lines at 110 to 160 DAS in 2009 and 171 DAS in 2010, the electrical conductivity (EC) in all soil samples was at least 3 mS/cm and in some cases exceeded 5 mS/cm under DI treatment. However, EC barely exceeded 3 mS/cm and no reduction in root length was observed under FI treatment. Correlation analysis of soil EC and root length density indicated that the root length declined when the soil EC exceeded 2.8 mS/cm. The main reason for the decrease of root length in cotton under DI was localized accumulation of salinity.

A 2-year field experiment was conducted (i) to study the effect of combined P and Zn fertilization on the Zn nutritional quality of wheat grown on potentially Zn-deficient calcareous soil and (ii) to identify which soil Zn fraction had the greatest effect on grain Zn concentration. Results showed that Zn fertilization increased grain Zn concentrations by 13 in 2006–2007 and 15 in 2007–2008. However, the application of 200 kg P2O5ha−1combined with Zn fertilizer reduced grain Zn concentrations by 38 in 2006–2007 and 17 in 2007–2008 compared with the control (no fertilizer treatment). The phytic acid (PA) concentration and the PA:Zn molar ratio in wheat grain increased as P fertilizer application rate increased, regardless of the Zn fertilizer application rate. Zinc fertilization alone increased diethyltriaminepentaacetic acid–Zn by 220 in 2006–2007 and 470 in 2007–2008 compared with the no Zn fertilizer treatment. The combined application of P and Zn also increased diethyltriaminepentaacetic acid–Zn and loose organic matter–bound Zn, but the increase became smaller as the P fertilizer application rate increased. In conclusion, P fertilizer application rates to the potentially Zn-deficient calcareous soil used in this study should be less than 100 kg P2O5ha−1to ensure the efficacy of the Zn fertilizer. Among the soil Zn fractions in this study, loose organic matter–bound Zn had the greatest correlation with grain Zn concentration.