Saline-alkali land amendment and value development: Microalgal biofertilizer for efficient production of a halophytic crop - Chenopodium quinoa

Saline-alkali land amendment and value development should be conducted simultaneously, and microalgal biofertilizer may provide an efficient solution. Here, a saline-alkali tolerant algae was selected and applied to saline-alkali land to reveal its effects on land amendment and quinoa production. The results showed that Chlorella pyrenoidosa showed best growth and photosynthetic characteristics with increasing saline-alkali stress. Whether planting quinoa (Chenopodium quinoa Longli No. 1) or not, the application of C. pyrenoidosa supplied soil available nutrients, held water retention, and notably the organic matter of saline-alkali land with quinoa cultivation after algal maximum dose (OD680 = 2.0) showed 64.7% more content than the control. Saline-alkali land caused 23.7% yield loss of quinoa, which was attributed to organic lack (3.093 g kg(-1)) and saline-alkali conditions (pH 9.49 and 119.3 mS m(-1) electrical conductivity). Algal addition improved the chlorophyll synthesis and effective quantum yield of quinoa, enhanced more absorbed light energy to involve in photosynthesis rather than heat dissipation, and promoted the synthesis of osmotic regulatory substances (soluble sugar and protein) and antioxidant (anthocyanin) to alleviated osmotic and oxidative stresses. The growth improvement of quinoa confirmed the greater effect of stress alleviation than growth stimulation that reflected 41.7% and 28.6% yield increases in saline-alkali and nonsaline-alkali lands. Overall, saline-alkali tolerant alga adjusted overground and underground parts, including amending soil properties as organic addition and nutrient supply, and strengthening the tolerance of quinoa to saline-alkali environment. This assessment supports a sustainable practice of applying stress tolerant alga for land amendment and halophytic crop production to develop saline-alkali land value.