Effects of Different Organic Fertilizers on Improving Soil from Newly Reclaimed Land to Crop Soil

The rapid development of cities in the recent 10 years caused a reduction in the cultivated land area, which only accounts for 14% of the total land area in China. Land development and reclamation have been regarded as an effective way to compensate farmland occupation. However, most of the newly reclaimed land has poor soil fertility and suitability; in some cases, the production capacity is only 10–30% of the occupied farmland. In order to ameliorate the soil quality of the newly reclaimed land, this study evaluated the effects of commercial organic fertilizer (0.75, 1.50, and 2.25 kg/m2), mushroom residue (1.50, 2.25, and 3.00 kg/m2), biogas slurry (150, 225, and 300 kg/m2), vegetable cake (0.30 and 0.60 kg/m2), and chemical compound fertilizer (37.50 g/m2) on the pH, moisture content and organic matter content (OMC), available phosphate, total nitrogen, alkaline hydrolysis nitrogen, microbial biomass carbon and nitrogen, and number of total bacteria and phosphate-solubilizing bacteria, as well as the growth of maize seedlings. The results from this study indicate that the soil quality (OMC is an indicator) was ameliorated by chemical and organic fertilizers, in particular commercial organic fertilizers, which caused a 9.35–16.35% increase in moisture content, a 11.56–18.72% increase in pH, a 1.73–2.15 fold increase in OMC, a 338.44–491.41% increase in available P, a 36.80–48.14% increase in total N, a 95.32–128.34% increase in alkaline hydrolysis N, a 92.57–178.38% increase in total bacterial numbers, and a 7.57–20.87 fold increase in microbial biomass carbon compared with the control. The pot experiment further indicated that soil amended with commercial organic fertilizers caused a 20.35–30.55% increase in the height and a 12.50–16.67% increase in the total dry weight of maize seedlings. In addition, representative strains with the ability to dissolve phosphorus and fix nitrogen were successfully isolated using the culture method, and were then identified based on colony morphological observation and 16S rDNA sequence analysis, which help us to not only understand why organic fertilizer has great effect on soil improvement, but also provides beneficial microbial resources for further study.

Challenges of organic agriculture for the production of composts and vermicompost for the production of medicinal plants – A socioeconomic demand

Although the demand for organic fertilizers in agriculture is growing, it remains incipient in some production sectors, such as medicinal plant production, which does not possess specific technology for its development. Solid residues are highly contaminant to water sources, soil, populations and biodiversity but can potentially be used to produce organic composts and vermicompost, such production not only enables nutrient recycling but also acts on soil conditioning, increasing soil organic matter and improving its physical, chemical and biological characteristics, as well as strengthening organic production with an emphasis on medicinal plant production. In this context, recommendations for and applications of organic fertilizers available in the market were reviewed; in addition, the imminent socioeconomic demand for organic compost and vermicompost production was contextualized based on residues from coffee and sugarcane production and cattle farming for application to the medicinal plant production chain. It is concluded that although these sectors produce a considerable amount of residues, they are not being reused in formulation of organic composts and vermicompost, and commercial organic fertilizers recommended for medicinal plant production were not found. Thus, the formulation of vermicomposting and composting from the reuse of agricultural residues, are potential social, economic technologies and tools to be valued and disseminated to traditional and family farmers.

Mineralization dynamics of different commercial organic fertilizers from agro-industry organic waste recycling: an incubation experiment

The mineralization process of different commercial organic fertilizers was investigated in controlled laboratory conditions. The soil was mixed with the following organic fertilizers: Emos CAP^®, Organ CAP^®, Sic Stal^® and urea (as a control) at the rate of 300 mg N/kg dry soil. Emos CAP^® is made of cattle and poultry manure, meat, bone meal and dried blood, Organ CAP^® is a product made of leather and skins, while Sic Stal^® contains cow and horse manure. During the incubation the concentration of NO₃^–-N, NH₄⁺-N, microbial biomass and carbon dioxide, nitrous oxide and ammonia emissions were determined. All fertilizers showed a peak of NH₄⁺-N after 7 days from the beginning of the test. The decomposition of Sic Stal^® caused a rapid rise of CO₂ production associated to the growth of microbial biomass while Emos CAP^® promoted a release of N₂O in the first 16 days. In conclusion, all the commercial organic fertilizers tested can be considered fertilizers with a fast release of N, among them Emos CAP^® and Sic Stal^® allow a rapid N supply to plants while Organ CAP^® could be used when the N request of plants is not immediate.