Ten-year productivity of irrigated lowland rice under different levels of organic and inorganic fertilizers

Joveno S. Lales

Issue Date

8-2008

Abstract

A long-term field experiment was conducted starting 1996 to evaluate the productivity and economics of growing lowland rice varieties using inorganic and organic fertilizers. The treatments were arranged using split plot design with three replications. The main plots were FT1 = inorganic fertilizer alone at recommended level (RIF), FT2 = commercial organic fertilizer (OF) alone at manufacturer's recommended level, FT3 = 75% RIF + OF, FT4 = 50% RIF + OF, FT5 = 25% RIF + OF, and FT6 = no fertilizer. The sub-plots were four lowland rice varieties, namely: PSB rc32 (modern highly-yielding variety), 'Burdagol,' 'Sampaguita,' and 'Sinandomeng' (farmers' varieties). Difference in grain yields were observed, attributed to the individual effects of variety and fertilizer treatments. PSB Rc32 and 'Sinandomeng' had comparable yields. These varieties out-yielded ' Burdagol' and ' Sampaguita.' Grain yields were generally lower during the dry season that wet season. Grain yield in FT1 was consistently and significantly higher than FT2 by 48% during the dry season and 11% during the wet season. Replacing 25% of the inorganic fertilizer with organic fertilizer significantly decreased grain yields during the dry season except in 1998 and 2000. Increasing further the level of replacement (50-100%) led to greater yield reduction. This declining trend was reversed in five wet season crop cycles, that is, grain yields significantly increased as the level of fertilizer substitution increased up to 50%. Based on the grain yield obtained in FT6, the inherent nutrient supply capacity of the soil was capable of supporting the crop to produce 45% and 78% of the yield obtained inFT1 during the dry and wet seasons, respectively. Net return was highest in FT3 during the dry season and in FT4 during wet season. Marginal cost highest in FT6 but marginal benefit was largest in FT4 during the wet season. Based on marginal benefit-marginal cost ratio, the most economically viable inorganic-organic fertilizer combination during the wet season was 50:50. The field study should be continued to evaluate the dynamics of N, P, and K balance as well as effectiveness of bio-fertilizer like Bio-N as substitute for inorganic N fertilizer on a long-term basis.

Source or Periodical Title

Philippine Journal of Crop Science

ISSN

0115-463x

Volume

33

Issue

2

Page

59-74

Document Type

Article

Frequency

tri-quarterly

Physical Description

tables

Language

English

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