Plant tolerance to herbivory affect plant growth and also tolerance are water, light, carbon dioxide and soil nutrients. Water and light levels are generally assumed to be positively associated with tolerance (Strauss and Agrawal 1999). However, there are exceptions such as evidence of decreased tolerance in "Madia sativa" with increased water availability (Wise and Abrahamson 2007, Gonzales "et al." 2008). Many studies have found CO levels to decrease tolerance in plants (Lau and Tiffin 2009). Increased nutrient levels are also commonly found to be negatively associated with tolerance (Wise and Abrahamson 2007). There are currently three prominent models that predict how resource levels may
Korean natural farming enhanced SI within 2 cropping cycles. KNF posits three primary stages of plant growth. Each stage requires a different balance of nutrients. In the growth phase, the plant extends its roots, branches and foliage. The key nutrient in this stage is nitrogen. KNF prefers the use of a preparation of fish amino acids for this phase. After the plant has reached sufficient size, the plant diverts its energy into making flowers to attract pollinators. The key nutrients in this stage are calcium and phosporous. KNF prefers the use of a preparation of fermented plant juice and other amendments for this