Abstract: As the indicators of nitrogenous fertilizer, NH₄Cl and KNO₃ were applied with six kinds of super absorbent polymer (SAP) to study the relationship between SAP and nitrogenous fertilizer. Water absorbency (WA) and fertilizer conservation of SAP were studied. The results show that the ionic strength of the nitrogenous solution, polymer type and particle diameter are the most important factors on WA of SAP. The amount of NH₄⁺ releasing and absorbing by SAP is much higher than that of NO₃^-. The ability of SAP releasing and absorbing nitrogenous fertilizer is influenced by the particle diameter and secondary component of SAP. The relationship between SAP and nitrogenous fertilizer is restrained by the composition and structure of SAP and the ion strength of the nitrogenous fertilizer solution. The results indicate that fertilizer conservation of SAP has the ability of absorbing nitrogenous fertilizer. It is important to disclose the mechanism of fertilizer conservation of SAP.