Effects of Nitrogen and Phosphorus Addition on Agronomic Characters, Photosynthetic Performance and Anatomical Structure of Alfalfa in Northern Xinjiang, China

Abstract

The productivity of alfalfa is associated with a large amount of nitrogen (N) and phosphorus (P); the addition of exogenous N and P fertilizers can fully exploit the growth potential of alfalfa. However, there is uncertainty about the relationship between changes in alfalfa productivity and photosynthetic physiology and anatomy. We conducted field fertilization experiments on alfalfa in the second and third years under drip irrigation, as well as measurement of the photosynthetic physiology, anatomical structure and agronomic traits of alfalfa at different levels of N (0, 120 kg·ha−1) and different levels of P2O5 (0, 50, 100 and 150 kg·ha−1). The results showed that the dry matter yield (DMY), crude protein (CP), net photosynthetic rate (Pn) and specific leaf weight (SLW) were increased by 2.10~11.82%, 4.95~11.93%, 4.71~7.59% and 2.02~7.12% in the N application treatment compared with the non-N application treatment, while the DMY, CP, Pn and SLW were increased by 3.19~17.46%, 1.99~8.42%, 6.15~24.95% and 2.16~11.90% in the P application treatment compared with the non-P application treatment. N and P increase the thickness of the spongy tissue (ST) of alfalfa, which will facilitate the entry and exit of gas and water, and will further affect the photosynthetic indexes, such as stomatal conductance (Gs) and transpiration rate (Tr), of alfalfa leaves. Increased palisade tissue (PT) thickness will also enhance the adaptability of plant leaves to strong sunlight, thereby increasing the maximum net photosynthetic rate (Pmax) and light saturation point (LSP). Fertilization treatment showed the highest utilization efficiency for low light and better adaptation to strong light, but the Rd decreased. The comprehensive scores of principal component analysis for anatomical structure, photosynthetic performance and agronomic traits were N1P2 > N0P2 > N1P3 > N1P1 > N0P3 > N0P1 > N1P0 > N0P0. Therefore, the application of N and P fertilizers contributed to the adaptive changes in alfalfa leaf anatomy and the improvement of photosynthetic capacity, which were beneficial to the improvement of alfalfa dry matter yield, growth traits and nutritional quality, with the most obvious improvement effect obtained with the application of 120 kg·ha−1 of N and 100 kg·ha−1 of P2O5.

Deficit irrigation combined with nitrogen application in the early growth stage of sugar beet increases the production capacity of canopy and avoids yield loss

“…These results are consistent with those of Sugiura et al 11 . High MVB XW and MVB PW values indicate high sugar and water transport capacity of phloem, which is not only beneficial to unload excess nonstructural carbohydrates in leaves, 11 but also provides sufficient water for crop leaves under deficit irrigation 41 . The VIP analysis also confirmed this finding.…”

Garlic-specific Fertilizer Improves Economic and Environmental Outcomes in China

“…3; Supplementary Table 1). Excessive P enhances plant respiration, which demands large amounts of sugar and energy; this thickens and darkens leaves while reducing the rate of photosynthesis (Malhotra et al 2018;Sun et al 2022). In addition, excessive P content can induce nutrient deficiencies in Fe, Zn, and Mg, as the combination of phosphate and metal ions forms insoluble substances in the soil (Osman and Osman 2013;Sharma et al 2013).…”

Characteristics of Carbon, Nitrogen and Phosphorus Stoichiometry and Nutrient Reabsorption in Alfalfa Leaves with Different Fall-Dormancy Levels in Northern Xinjiang, China

“…It has also been shown that lowlatitude areas can lead to lower over-summering rates of alfalfa due to high temperatures and continuous rainfall. Additionally, soil nutrients and beneficial microorganisms may vary increasingly with the growing year due to the inconsistent growth characteristics and nutrient requirements of different alfalfa varieties [31]. In conclusion, the growth differences of different fall-dormancy alfalfa are mainly influenced by various factors such as latitude, climatic environment, and their own genetics.…”