Nitrogen Nutrition Optimization in Organic Greenhouse Tomato Through the Use of Legume Plants as Green Manure or Intercrops

Abstract

In the present study, in addition to farmyard manure (FYM), cowpea was applied as green manure and faba bean as an intercrop in an organic greenhouse tomato crop, aiming to increase the levels of soil N. Three experiments (E1, E2, E3) were carried out, in which legumes were either noninoculated or inoculated with rhizobia alone or together with plant growth, promoting rhizobacteria. Inoculation of legumes with rhizobia considerably increased N2 fixation in E1 but had no impact on N2 fixation in E2 and E3. In E1, the application of cowpea decreased yield because it imposed a stronger nematode infection as the cowpea plants acted as a good host for Meloidogyne. However, in E2 and E3 the nematode infection was successfully controlled and the legumes significantly increased the tomato yield when inoculated in E2, irrespective of legume inoculation in E3. The total N concentration in the tomato plant tissues was significantly increased by legume application in E2 and E3, but not in E1. These results show that legumes applied as green manure can successfully complement N supply via FYM in organic greenhouse tomato, while legume inoculation with rhizobia can increase the amounts of nitrogen provided to the crop via green manure.

Impact of Legumes as a Pre-Crop on Nitrogen Nutrition and Yield in Organic Greenhouse Tomato

“…The %Ndfa ranged low in all treatments compared to values reported for the same legume species by Gatsios et al [19], who worked in the same greenhouse soil, and by other investigators, who worked in different locations [25,26]. This is attributed to the high concentration of soil inorganic N, especially NO 3 , which ranged from 73 to 95 mg kg −1 when the legumes were sowed.…”

“…The N derived from the atmosphere in the aboveground biomass of legumes was determined by applying a method based on the natural abundance of 15 N in plant tissues relative to the air [ 19 , 54 , 55 ]. To apply this method, the stable N isotopic composition of legume tissue samples was determined using an Isoprime 100 continuous flow isotope ratio mass spectrometer coupled to a Vario Isotope Select elemental analyzer (Elementar Analysensysteme GmbH, Hanau, Germany).…”

“…Legumes, i.e., plant species belonging to the Fabaceae family, form symbiotic relationships with N 2 -fixing bacteria, generally termed rhizobia, and, therefore, legume-based green manure can provide significant amounts of N to the succeeding crops [ 15 , 16 , 17 ]. Several studies have shown that the use of legumes as green manure can effectively enhance the yield of the following tomato crop [ 17 , 18 , 19 ]. Different legume species are colonized by different rhizobial species.…”

“…Different legume species are colonized by different rhizobial species. Therefore, when the appropriate rhizobial species for a particular legume crop are not present in the soil accommodating this crop, inoculation is necessary for sufficient biological N 2 fixation that can effectively increases the total amount of produced biomass [ 19 , 20 ].…”

Nematicidal Amendments and Soil Remediation

“…Crop rotation and incorporation can also affect soil bacteria populations, which in turn may affect phytoparasites. There are many reports on the nematicidal activity of plant growth-promoting rhizobacteria (PGPR) colonizing different cover crop rhizospheres [150][151][152][153]. PGPR produce a wide range of plant growth substances, for instance gibberellins, auxins, cytokinins, and ethylene [154], and in combination with composts PGPR limit pest damage to plants [155].…”