Document Type

Capstone Project

Degree Name

Bachelor of Science (B.S.)


Science & Environmental Policy


urrent fertilizer practices are loading the soil of the Salinas Valley with nitrogen. New fertilizer management aimed at slowing nitrogen leached into water tables and reducing economic loss due to excess or lost nitrogen is very important. A study was conducted on four fields growing romaine lettuce in the Salinas Valley of California to test and implement an effective nitrogen fertilizer application. Using Pre-sidedress Nitrate Testing Kits (EMQuant) the soil of each treatment field was tested to determine the amount of fertilizer that should be applied to each site. The control fields were fertilized using conventional farming practices from the preceding year and the farmer's local knowledge of weather conditions. A t-test comparing percent of plants harvested, carton weights and leaf nitrogen between treatment and control showed that the mean values are not significantly different between control and treatment. Therefore the PSNT kits can be used to reduce fertilizer application without a reduction in lettuce yield or quality. A nitrogen budget analysis was also conducted to assess the amount of nitrogen, referred to as lost nitrogen, left in the soil after harvest. Input and output nitrogen that was calculated with the nitrogen budget was used to run a cost benefit analysis. The cost benefit analysis showed that the benefits from using the PSNT kits outweighed the cost of excess nitrogen over two years. This study suggests that if the testing kits were subsidized, more agriculture producers would use these kits.


Capstone Project (B.S.) Earth Systems Science & Policy Institute