Decoupling of P from C, N, and K Elements in Cucumber Leaves Caused by Nutrient Imbalance under a Greenhouse Continuous Cropping System

Abstract

There is insufficient information regarding the stoichiometric variation and coupling status of carbon (C), nitrogen (N), phosphorus (P), and potassium (K) in the leaves of nutrient-enriched greenhouse agroecosystems with increasing planting time. Therefore, we assessed the variation in elemental stoichiometry ratios in soil and cucumber (Cucumis sativus L.) leaves, and the coupling status of elemental utilization in the leaves under continuous cropping systems using natural (only soil; i.e., control soil, CO) and artificial (soil + straw + chicken + urea; i.e., straw mixture soil, ST) soil via monitoring studies for 11 years in a solar greenhouse. Soil organic C, total N, and total P concentrations increased by 63.4%, 72.7%, and 144.3% in the CO, respectively, after 11 years of cultivation (compared to the first year), and by 18.1%, 24.3%, and 117.7% in the ST under continuous cropping conditions, respectively. Total K concentrations remained unchanged in both soils. Moreover, the availability of these soil elements increased to different degrees in both soils after 11 years of planting. Additionally, the leaf P concentration increased by 9.8% in the CO, while leaf N and K concentrations did not change, suggesting decoupling of P utilization from that of N and K in leaves under a continuous cropping system. These findings suggest that imbalanced soil nutrients under continuous cropping conditions results in decoupling of P from N and K in the utilization of leaf nutrients.

Insights into Pyrroloquinoline Quinone (PQQ) Effects on Soil Nutrients and Pathogens from Pepper Monocropping Soil under Anaerobic and Aerobic Conditions

“…The fact that there was an adaptive coevolutionary relationship between rhizosphere soil microbes and plant root systems in the long term then formed a reciprocal relationship between plant and soil microbial community ( 4 , 5 ). However, under continuous monocropping and unreasonable fertilization, the balance of the relationships built by the soil-microbes-plant group is broken, and soil physicochemical and biological characteristics are changed ( 4 , 6 – 8 ). In the end, the soil quality of vegetable planting croplands is declining, and the nutrient deficiency is more and more serious, which seriously restricts the sustainable development of vegetable production ( 4 , 9 ).…”