Which spatial arrangement of green manure is able to reduce herbivory and invasion of exotic grasses in native species?

The practice of using green manure for ecological restoration has grown so significantly that there is a shortage of seeds for purchase on the market. Nonetheless, there is very little literature available demonstrating the effects and benefits commonly cited for green manure for addressing important environmental filters, such as herbivory and invasive grasses. Our objective is to determine which spatial sowing arrangement including green manure promotes the lowest rates of herbivory on native species and decreases cover by invasive grasses in ecological restoration. We experimentally tested three sowing configurations of green manure intercropping with native species: T1 the lowest herbivoy rate for both native and green manure, mixture of native and green manure species in the same row, T2, alternating rows of green manure and native species, and T3, rows of native species intercropped with a 2 m wide strip of green manure. We found that (1) green manure species experience greater damage from herbivory than do native species, with average values ranging from 1.8 times higher values in green manure than natives in T1, 2.9 times in T2, and 2.7 times in T3 (when sown in rows and in broader strips, green manure and native species attract more herbivorous insects than if they were sown together [muvuca]); and (2) when green manure and native species are planted mixed in the same row they produce greater soil cover, and thus limit invasion by undesired species. The use of green manure has been identified as an alternative method for overcoming the environmental filters of herbivory and invasive grasses in restoration areas. Considering the demand for information that supports the use of green manure for purposes of ecological restoration, the novel results of the present study fill a void and should prove to be of great interest to researchers and practitioners. In addition, the presented results provide information on efficient and low-cost restoration techniques that are necessary for the activity to gain scale, enabling countries to meet the large restoration targets.