Long-term effect of organic manures and inorganic fertilizers on soil organic carbon and nitrogen fractions in rice-wheat system
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Date
2011
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Publisher
CCSHAU
Abstract
Thirteen years of continuous cropping without any fertilization or with inadequate supply of nutrients in
imbalanced manner led to loss of total organic carbon over its initial level in soil. The per cent increase in soil organic
carbon was 49.0, 39.2, and 13.7 % over mineral fertilizer treatment (N150P75K75Zn25) in pressmud, farmyard manure and
green manure amended treatments, respectively. The content of all four organic carbon fractions increased significantly over
control by use of combined application of organic manures with inorganic fertilizers. The pressmud, farmyard manure and
green manure amended treatments accumulated significantly higher organic carbon fractions than burnt rice husk and
N150P75K75Zn25 treatments. On an average, the heavy fraction carbon constituted the major portion (about 80.7%) of the total
soil organic carbon.
Continuous rice-wheat cultivation for 13 years without any fertilization was unable to maintain total soil nitrogen
level to its original level and resulted in decrease at 8 mg N kg-1 year-1. Likewise, all the N fractions recorded a significant
decrease over their initial levels in the soil. The increase in total N content with the application of farmyard manure,
pressmud and green manure plus inorganic fertilizer treatments over mineral fertilizer only treatment (N150P75K75Zn25) was
23.1, 34.4 and 7.0%, respectively. All the four hydrolysable N fractions and non-hydrolysable N registered significant
increase due to inorganic fertilizers or organic amended treatments over their respective initial status. On an average,
amino acid-N, amino sugar-N, ammonia-N and hydrolyzable unknown-N constituted about 27.4, 10.2, 28.2 and 34.2 per cent
of the total hydrolysable-N after wheat harvest, respectively.
Balanced application of nutrients (N150P75K75Zn25) increased the grain yield of rice significantly as compared to
control or inadequate supply of nutrients to rice. Application of FYM along with fertilizers increased rice grain yield by 5.0
q ha-1 over that obtained with mineral fertilizer only treatment (N150P75K75Zn25). The grain yield of rice did not differ
significantly among press mud, green manure, burnt rice husk and mineral fertilizer only treatments (N150P75K75Zn25).
Application of N75P37.5K37.5Zn25 in green manured plot produced rice grain yield similar to that obtained with N150P75K75Zn25
treatment indicating a saving of approximately 50% of inorganic fertilizers with Sesbania green manuring.
The residual effect of FYM, press mud and green manure on the grain yield of succeeding wheat crop was positive
but significant effect was observed only for FYM treatment. Among the organic manures treatments, the highest uptake of
macro-and micronutrients by rice crop was observed with FYM, followed by green manure and press mud treatments.
Description
Keywords
Organic fertilizers, Fertilizers, Carbon, Crops, Rice, Farmyard manure, Fractionation, Crop residues, Diseases, Green manures