Nitrogen fertilizer application and planting densities were key limiting factor for the physiological metabolism and growth of Avena sativa L. In the paper, it was set five nitrogen fertilizer application (including: N1:225 kg/hm², N2:300 kg/hm², N3:375 kg/hm², N4:450 kg/hm², N5:525 kg/hm²) and four planting densities (including M1:3 million plants/hm², M2:3.5 million plants/hm², M3:4 million plants/hm², M4:4.5 million plants/hm²), and measure plant height, aboveground biomass, underground biomass, total biomass, stem biomass, leaf biomass, root biomass and ear biomass, and calculate stem/leaf ratio, root/crown ratio, stem contribution rate, leaf contribution rate, root contribution rate and spike contribution rate, to study the effect of density and nitrogen fertilizer on height, biomass and material distribution of Avena sativa L to provide scientific basis for water and fertilizer management of Avena sativa L in Horqin Sandy Land (Science and Technology Park of Inner Mongolia university for nationalities). The results showed, The main purpose was to harvest aboveground biomass such as oat stem and leaf, the optimal density and nitrogen fertilizer combination was M4 and N3, and aboveground biomass was 4254.96 g/m² (2017) and 4226.21 g/m² (2018). Under the same planting density, the height, aboveground biomass and underground biomass of Avena sativa L all showed first increased and then decreased with the rising of fertilizer application and the biggest height value appeared at N3. Under the same nitrogen fertilizer application, the height indicated increased gradually with the rising of density, and higher biomass was obtained under lower nitrogen fertilizer application and higher planting density conditions (such as:N1 conditions, the biggest value of underground biomass and total biomass was obtained under M1 condition), and under higher nitrogen fertilizer application conditions the higher value of biomass was obtained under lower planting density condition (M1 (2017) and M2 (2018) under the condition of N5 treatment, the aboveground biomass and total biomass were the highest, while M4 (2017) and M3 (2018) underground biomass was the highest.). Under same nitrogen fertilizer application conditions, the root/shoot ratio and stem/leaf ratio all showed increased first and then decreased with the rising of density. Under same density conditions, the root/shoot ratio and stem/leaf ratio indicated different variation laws with different nitrogen fertilizer application amount. The changes laws of root contribution rate, stem contribution rate, leaf contribution rate and ear contribution rate were different due to density and nitrogen fertilizer application.

This study aimed to determine the effects of delayed harvest, irrigation and nitrogen fertilization on yield and fuel quality of the Jerusalem artichoke (JA) (Helianthus tuberosus L.). The biomass, calorific value, ash content and total calories per hectare of the Jerusalem artichoke were assessed in Inner Mongolia, China, at various harvest times, after irrigation and nitrogen application. The results showed that fresh and dry weights of tubers and underground biomass were higher when harvested after freezing; the dry yields of leaves and stems decreased with harvest time. In addition, irrigation significantly enhanced the yields of underground biomass, aboveground biomass and tubers, compared with non-irrigation conditions (p < 0.05). Interestingly, the highest yield was obtained with irrigation and treatment with nitrogenous fertilizers (20 to 50 kg ha⁻¹). The calorific values of tubers and roots were significantly higher for samples harvested after freezing (p < 0.05); the calorific values of leaves and stems significantly decreased with harvest time and without irrigation (p < 0.05). The calorific values of stems and leaves were higher than those of tubers and roots, when JA was harvested before freezing, and the opposite trend was obtained for harvest done after freezing. The highest calories per hectare was obtained in WN2 (585247.42 MJ ha⁻¹) on 30 September 2010 harvest. No correlation was found between the effects of water or nitrogenous fertilizers and ash content. However, the ash contents of stems, leafs, tubers and roots were significantly decreased (p < 0.05) with harvest time. Finally, in all treatment conditions, leaves produced the highest ash amounts among all plant parts, including stems, tubers, leaves and roots.

The Horqin Sandy Land in China is a key alfalfa production base, challenged by low winter temperatures and large diurnal temperature shifts, affecting alfalfa’s winter survival. Alfalfa roots are the primary organs responsible for winter adaptability; consequently, by investigating the changes in the root physiology and nutritional components of alfalfa during the overwintering period, we can enhance our understanding of its mechanisms for cold resistance. Over the course of two years (2022–2023), field trials were conducted on 40 alfalfa varieties selected from both domestic and international sources for their potential cold resistance. This study assessed winter survival rates and analyzed root contents, including soluble sugars, starch, soluble proteins, and the concentrations of carbon (C), nitrogen (N), phosphorus (P) and their stoichiometric ratios. Principal component analysis, subordinate function analysis, and cluster analysis were employed for comprehensive evaluation. Biochemical markers varied significantly across varieties. The C, N, and starch contents in the roots were the main factors determining cold resistance. The varieties were categorized into four groups: Category I included five highly resistant varieties (‘Baimu 202’, ‘WL168HQ’, ‘Zhongmu No. 1’, ‘Gongnong No. 1’, and ‘Legacy’); Category II consisted of six moderately resistant varieties; Category III included twenty-eight slightly resistant varieties; and Category IV contained one non-resistant variety (‘3010’). This study recommends the adoption of the five varieties in Category I to enhance alfalfa cultivation in the Horqin region. This research provides valuable theoretical and practical guidance for improving the cultivation of alfalfa in the cold regions of northeastern China, supporting the development of the local livestock industry.

The effects of stomatal factors of plant leaves under partial root-zone drying (PRD) have been widely studied. However, the non-stomatal factors and the relationship between photosynthesis with soil moisture have not been explored. In this study, four treatments over-irrigation, full irrigation, moderate water deficit, and severe water deficit were investigated, aiming to evaluate the effects on the diurnal variation of alfalfa leaf photosynthesis under PRD and its relationship with stomatal and non-stomatal limitations, as well as soil moisture. The results showed that any levels of water deficit led to a decrease in the photosynthetic rate (P_n) of alfalfa leaves. Leaves under moderate and severe water deficit displayed a pronounced midday “photosynthetic lunch break,” while those under over- and full irrigation did not display this phenomenon. Before 11:30 a.m., the reduction in P_n was primarily due to stomatal limitations, as evidenced by reduced stomatal conductance (G_s) and decreased intercellular CO₂ concentration (C_i). After 11:30 a.m., non-stomatal limitations became the dominant factor, with both G_s and transpiration rate (T_r) continuing to decrease, while C_i increased, indicating a shift in the limiting factors. Under PRD with moderate water deficit, alfalfa experienced both stomatal and non-stomatal limitations within a single day, leading to a hay yield reduction of 18.6%. Additionally, over-irrigation helped to maintain higher P_n and T_r, increasing alfalfa yield and thus improving water productivity by 33.1%. The correlation coefficients between soil moisture content at 10 cm depths with alfalfa leaf P_n, T_r, and G_s on the photosynthetic measurement day were 0.9864, 0.8571, and 0.8462, respectively. At 20 cm, the correlation coefficients were 0.8820, 0.6943, and 0.6951, respectively. The study concluded that both stomatal and non-stomatal mechanisms contributed to reduced alfalfa P_n in water deficit of PRD. Furthermore, shallow soil moisture also played a crucial role in influencing photosynthetic performance.

Transforming land use patterns prevents and controls desertification. In the Horqin Sandy Land, we evaluated the soil restoration effects of planting corn (from 2014 to 2018) on previously uncultivated land (in 2013), followed by the transition to alfalfa cultivation under five nitrogen application levels (from 2019 to 2023). After corn cultivation, the soil available nitrogen (AN), C/N ratio, C/P ratio, and N/P ratio decreased by 39.02%, 7.14%, 21.35%, and 12.83%, respectively, compared to those of uncultivated land. However, following the planting of alfalfa, especially in 2023, the bulk density values were the lowest, while the AN, soil organic carbon, total nitrogen, and total phosphorus values were the highest. An AHP-fuzzy comprehensive evaluation showed that the available phosphorus (AP), SOC, C/N, C/P, and N/P had significant weights of 0.12, 0.128, 0.133, and 0.128, respectively, and thus were key soil quality determinants. The soil quality assessment values for the N1 and N2 treatments were the highest at 0.208 and 0.202, respectively. Conclusively, the intensive cultivation of alfalfa under 51.75 and 103.5 kg/ha N improves soil fertility. This study provides theoretical support for the restoration of desertified soils in the Horqin Sandy Land.