Effect of compost enriched with N and L-tryptophan on soil and maize

Abstract

-Composting provides an excellent way to manage the huge volume of organic waste and convert it into a useful soil amendment. The effectiveness of composted organic waste can be further improved by enriching and blending it with nutrients and biologically active substances. The resulting value-added composts can be used at substantially low rates such as a few hundred kg per ha compared with conventional use of organic wastes in tons per ha. This approach could have practical significance in reducing the use of chemical fertilizer for sustainable agriculture and the environment. L-tryptophan is a precursor of the growth hormone indole acetic acid and is known to stimulate plant growth at extremely low concentrations. Here, we studied the effect of composted fruit and vegetable wastes, enriched with N at 133 g kg −1 compost, with or without L-tryptophan at 10 mg kg −1 compost, on soil and maize crops. The enriched compost was applied at 300 kg ha −1 to a sandy clay loam soil either by mixing with the top 15-cm soil layer in pots or as a band placement along the maize plants grown in the field. The compost was applied alone and in combination with 40 or 80 kg ha −1 urea N and compared with a treatment containing 160 kg N ha −1 , a full dose of N fertilizer alone, while P and K fertilizers were applied in all the treatments. Our results show that application of the enriched compost to soil increased aggregate stability by up to 24.8% and water retention by up to 43.1% compared with untreated control. A gradual increase in the concentration of indole acetic acid in compost, ranging from 1.02 to 3.34 mg kg −1 , was observed when compost was treated with its precursor L-tryptophan. The results of pot and field experiments revealed that compost enriched with N and L-tryptophan in the presence of 80 kg N fertilizer significantly increased cob and grain yields, by up to 19.8 and 21.4%, respectively, compared with a full dose of N fertilizer. These findings suggest that enrichment of composted organic wastes with N and L-tryptophan can change them into a value-added organic product that could be used as a soil amendment at rates as low as 300 kg ha −1 to increase crop production on a sustainable basis.auxins / biologically active substances / maize / nitrogen / organic fertilizer / organic waste / recycling soil aggregate

Integrated use of Rhizobium leguminosarum, Plant Growth Promoting Rhizobacteria and Enriched Compost for Improving Growth, Nodulation and Yield of Lentil (Lens culinaris Medik.)

“…Furthermore, OM maintains the dynamics and productive potential of the "rhizosphere". Organic matter improves soil structure, increases water retention capacity, stimulates soil microbes, and provides nutrients (Fontaine et al, 2003;Ahmad et al, 2008a;2008b;Shahzad et al, 2008;Reid et al, 2011a;2011b). The supplementary effect of compost may also be attributed to better supply of the organic C and energy required by heterotrophs, consequently, more and efficient establishment of PGPR producing better results.…”

“…Organic waste materials were composted as described by Ahmad et al (2008a). From the composted organic waste materials, 50% PEC was prepared by enrichment with 50% of full dose of phosphatic fertilizer using single super phosphate (SSP) as the source of P while remaining 50% P was applied at the time of sowing.…”

“…Moreover, maintenance of high bacterial population in the rhizosphere improves the efficiency of these organisms (Cheuk et al, 2003;Ahmad et al, 2008a;2008b). This high bacterial population can be maintained by the application of enriched compost which supports their growth and activities (Cheuk et al, 2003).…”

Production and storage of N-enriched co-compost

“…Urea and ammonium sulphate fertilisers are available on the local market and popularly used by Ghanaian farmers. Ahmad et al (2008), Bangar et al (1989), Rao et al (2007), and Sridhar and Adeoye (2003) reported on the use of urea or ammonium sulphate to enrich compost to obtain a compost-fertiliser product. However, they did not address the effect of these two N sources (urea or ammonium sulphate) on the final N content of the compost-fertiliser product; the form(s) of urea or ammonium sulphate (i.e.…”

“…dry, paste or liquid) that could blend best with co-compost and the effect of storage on the properties of the N-enriched co-compost. For instance, Ahmad et al (2008), Bangar et al (1989), Han et al (2004) and Sridhar and Adeoye (2003) used urea, whereas Rao et al (2007) used ammonium sulphate. Furthermore, Ahmad et al (2008), Rao et al (2007) and Sridhar and Adeoye (2003) applied the inorganic fertiliser in dry form, but Bangar et al (1989) and Han et al (2004) dissolved it in water.…”