Strategies for enhancing the nutritional value of peas for human consumption – fertilization versus genotype effects

Summary

Introduction: Enhancing the nutritional value of peas (Pisum sativum L.) for human consumption has traditionally focused on nitrogen fixation and the protein content. However, there has been limited research on plant nutrition and fertilization strategies for peas, targeting nutrients other than nitrogen.
Purpose and aim: The overall aim of our study was to investigate methods to increase the nutritional value of peas for human consumption through genotype choice and fertilization strategy. The study aimed to increase the contents of iron (Fe), zinc (Zn), and sulphur (S) in two pea genotypes. The research questions were: i) do different pea genotypes respond similarly to fertilizer treatments, ii) can the content of Fe, Zn, and S be increased in the harvested product, and iii) can nutritional enhancement be obtained by both inorganic and organic fertilizers?
Methods: The two pea genotypes; cv. ‘Ingrid’ and the landrace ‘Brunart fra Nakskov’, are contrasting in morphology and origin, and both are currently used for food in Denmark. Both genotypes were fertilized with either an inorganic sulphur, phosphorus and potassium combination, an organic compost application or grown without soil amendments. Plants were grown to maturity under both field and greenhouse conditions. The peas were analysed with IR-MS and ICP-OES to reveal variation in yield, protein content, and nutrients including Fe, Zn and S.
Results: While the protein content of pea seeds in the field experiment only ranged from 17,6 to 24 % of dry matter (36% increase), the Fe content ranged from 20 mg kg-1 to 64 mg kg-1 (220% increase) and the content of S ranged from 1028 mg kg-1 to 2014 mg kg-1 (96% increase). Like Fe and S, the contents of Zn and calcium (Ca) showed large variation, while potassium (K), magnesium (Mg) and phosphorus (P) showed less or no variation. The contents of Fe, Zn and Ca were almost solely affected by genotype. Fe and Zn were highest in ‘Brunart fra Nakskov’, and Ca highest in ‘Ingrid’. In contrast, S was highest following the inorganic fertilizer treatment regardless of genotype.
Conclusions: When considering the nutritional value of peas for human consumption, a narrow focus on yield and protein is inadequate. Instead, more emphasis should be placed on the content of plant nutrients. Depending on the element in question, either fertilizer strategy OR genotype choice is most important. This has implications for which route to take when planning for future, more nutritious plant-based food products.