Effects of rice straw incorporation on phosphorus and zinc availability in rice-wheat sequence
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Date
2019
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Punjab Agricultural University, Ludhiana
Abstract
The present study was conducted to investigate the effects of rice straw (RS) incorporation on
P and Zn availability in surface (0-15 cm) soil under rice-wheat cropping sequence. The
treatments were N application (0, 90, 120 and 150 kg ha-1, main plot) and RS incorporation
(0, 5, 7.5 and 10 t ha-1, sub plot).Inorganic-P was dominating fraction (92% of total-P), while
organic-P constituted only 8%. Relative preponderance of inorganic P fractions followed an
order: calcium bound P (Ca-P) > aluminium-P (Al-P) > iron-P (Fe-P) > reductant soluble-P
(Red-P) > saloid-P. Nitrogen and RS incorporation significantly (p<0.05) increased the
concentration of inorganic P fractions, with highest concentration in RS10 and N150 treatments.
The sequential extraction procedure for Zn fractionation showed the dominance of residual
fraction (Res-Zn), and their relative abundance in the surface soil followed an order: water
soluble and exchangeable Zn (WS+EX-Zn) < specifically adsorbed Zn (SpAd-Zn) <
manganese oxide bound Zn (MnOx-Zn) < organic matter bound Zn (OM-Zn) < amorphous
iron bound Zn (AFeOx-Zn) < crystalline iron oxide Zn (CFeOx-Zn) < Res-Zn. These Zn
fractions were significantly increased with graded levels of RS incorporation. Increase in P
fractions showed a linear positive relationship with SOC and available-P in soil. Zinc
fractions were positively and linearly correlated to SOC and DTPA-Zn concentration.
Maximum wheat grain yield was observed with N120 and RS7.5 treatments. Highest P and Zn
uptakes were observed under RS10 treatment. These results showed that N application and RS
incorporation significantly increased the P and Zn concentration in soil under rice-wheat
cropping system.
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