Nitrogen Sources for Organic Vegetable Crops

Abstract

<jats:p>Fertilization is the most expensive cultural practice for the increasing numbers of organic vegetable growers in the United States. Nitrogen (N) is the most important and costly nutrient to manage, and cost-effective N management practices are needed for efficient organic vegetable production. There is a wide array of organic N sources available, but they vary in cost, N content, and N availability. Compost and cover crops are commonly used sources of N for vegetables because they are relatively inexpensive and offer additional nutrients or soil improvement qualities in addition to N. Studies have shown that compost quality factors that affect N mineralization vary by source and among different batches from the same source. Compost carbon to N ratio should be equal to or less than 20:1 to assure net short-term mineralization. Cover crops also vary in N content and mineralization rate after incorporation. Leguminous cover crops decompose and release N more rapidly than grass or cereal cover crops at the preheading stage typically incorporated. Even the most efficient N-supplying composts, cover crops, or other organic N sources do not release appreciable N to a subsequent crop beyond 6 to 8 weeks from incorporation, and this burst of early N may not synchronize with N requirements for many vegetable crops. Other potential organic fertilizer N sources have been evaluated for vegetables, and they vary in N cost and N mineralization rate. Materials evaluated include seabird guano, liquid fish, feather meal, corn meal (<jats:italic>Zea mays</jats:italic>), blood meal, and liquid soybean meal (<jats:italic>Glycine max</jats:italic>) among others. Of those evaluated, feather meal, seabird guano, and liquid fish stand out as more economical organic sources of available N. Organic sources generally lack uniformity and are bulky, unstable, and inconsistent as a group, and this contributes to additional hidden management costs for organic growers. Liquid organic N sources for use in microirrigation systems may have additional disadvantages caused by loss of valuable nutrient N that is removed by filters.</jats:p>

Advances and Trends in Organic Fruit and Vegetable Farming Research

“…Furthermore, for irrigated organic vegetables grown under arid subtropical climate conditions, a very fast turnover of the amendments resulted in high C and N volatilization (Siegfried et al 2011). Consequently, sources, rate, timing, and method of amendment application will influence soil temperature, soil moisture, and nutrient availability (Gaskell and Smith 2007). Regrettably, few quantitative studies have been conducted on the nutrient release of surfaceapplied mulches, as found for fruit trees and perennial berries, in comparison with incorporated materials.…”

Optimization of hydrolysis condition of blood meal by Bacillus subtilis with response surface methodology

“…For high-level production of neutral protease we developed a strain, via UV mutagenesis, using Bacillus subtilis CICC 10265 as parent strain in this study. After being processed, the digestibility of the protein, which replete with FAAs and peptides of various molecular weights, is improved (Guo et al, 2007;Gaskell and Smith, 2007), and the product is easily absorbed (Rust, 1995).…”

Mineralizable soil nitrogen and labile soil organic matter in diverse long-term cropping systems

“…Nitrogen limitations are often an important factor limiting corn grain yield in organic systems (Berry et al 2002;Cavigelli et al 2008). Nitrogen management in organic cropping systems requires an integrated strategy of incorporating crop and cover crop residues and animal manures into soil to build and maintain soil organic matter and mineralizable soil N levels (Gaskell and Smith 2007;Berry et al 2002). Managing these systems sustainably requires that the buildup of mineralizable soil N be taken into consideration so that sufficient, but not excessive, rates of N inputs can be determined.…”