A Trade-Off between the Growing Performance and Sowing Density of Sunflower (Helianthus annuus L.) under Fertigation in an Arid Saline Area

Abstract

Sunflower is one of the pioneer crops cultivated in salt-affected arid areas. The influences of sowing density on the growth performance of this crop under fertigation conditions have not been well studied. This study arranged four sowing density treatments, 41,667, 35,714, 31,250, and 27,778 plants ha−1, marked as D30, D35, D40, and D45, respectively, to reveal the relationships between soil salinity, growth performance, and sowing density under drip fertigation conditions. The results showed that the electrical conductivity of saturated paste extracts (ECe) decreased during the growing seasons but increased on the topsoil during the non-growing seasons in all of the treatments. The sowing densities had remarkable influences on the ECe in the 0–40 cm soil layer (ECe-40). The average ECe-40 during the two seasons for treatments D30–D45 correspondingly decreased by 7.0%, 33.9%, 11.1%, and 15.8% when compared to the original value. The soil pH in the 0–40 cm soil layer during the two seasons for treatments D30–D45 correspondingly decreased by −0.03, 0.20, 0.20, and 0.27 when compared to the original value. Increasing the spacing in the rows could promote the stem diameter, plant biomass, and proportion of biomass allocated underground. The yield and related yield components in this experiment under fertigation were significantly higher than those under surface irrigation. A sowing density between 31,250 and 35,714 plants ha−1 could ensure both the high yield and high morphological quality of the seeds, which could be recommended for sunflower cultivation under drip fertigation conditions.

The Responses of Stem and Leaf Functional Traits of Medicago sativa and Bromus inermis to Different Mixed Planting Patterns

“…Stem and leaf traits are intrinsic physiological and external morphological measures of adaptive responses developed by plants in response to environmental changes. The traits are closely related to plant biomass, plant access to and utilization efficiency of resources [28], and the survival strategies adopted by plants to obtain maximum material harvest [29]. In this study, we found that alfalfa stem and leaf traits of the first sampled crop in the first year were significantly higher under the alfalfa-awnless brome mixed treatment than under the hetero-row mixed and monoculture treatments.…”

Cropping Systems and Agronomic Management Practices of Field Crops

“…In addition, in the present Special Issue, attention has also been paid to the combined effect of fertilization with weed management [16], irrigation [17,18], the crop establishment method [19], crop variety [20], sowing density [21,22], seed priming [23], and fungicide application [24]. For instance, with regard to the fertilization-irrigation combination, Abdou et al [17], in light of the water shortage caused by climate change, proposed a new agro-management practice (deficit irrigation and higher nitrogen fertilizer) for lowland rice in semiarid conditions as an alternative to the flooding system.…”