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A field experiment based on a monolith method using flooding irrigation under mulch film (FI) as a control was conducted to investigate soil salinity dynamics under drip irrigation with mulch film (DI) and its effects on cotton root length. The average soil salinity increased with duration of irrigation, but salt distribution in the soil profile was uneven and showed strong accumulation in the soil between adjacent mulch films. With advancing growth of cotton plants, the area of salt accumulation gradually expanded, especially from 110 to 125 days after sowing (DAS), when salinity distinctly increased in the 0- to 40-cm soil depth and at distances 30–70 cm from drip lines; the electrical conductivity (EC) under DI in all soil samples was at least 3 mS cm−1and in some cases exceeded 5 mS cm−1. Root length declined significantly by 18.1% from 110 to 125 DAS under DI. The soil area showing the greatest decline in root length under DI coincided with the main site of salt accumulation. Correlation analysis of soil EC and root length density indicated the root length declined when soil salt content exceeded 2.8 mS cm−1. However, under FI salt accumulation barely exceeded 2.8 mS cm−1and no reduction in root length was observed. The results indicated that the main reason for decreased root length in cotton under DI was localized accumulation of salinity. [ABSTRACT FROM AUTHOR]

Excessive application of nitrogen fertilizers and improper methods of irrigation under conventional management are common problems in the cotton fields of northwestern China. Efficiency-enhanced management, based on the water and nitrogen dynamics and crop requirements, has been used as a valuable strategy in different crops. The present study aimed to compare efficiency-enhanced management and conventional management of irrigation and nitrogen fertilization in the cotton fields at the Junggar Basin (Shihezi) and Tarim Basin (Cele) of northwestern China. Compared with conventional management, efficiency-enhanced management reduced the amount of N fertilizer by 41% in Cele and 44% in Shihezi, and the irrigation quantity by 35% in Cele and 24% in Shihezi. However, the cotton yield under efficiency-enhanced management was similar to that found under conventional management at both the experimental sites. The efficiency-enhanced management increased the water-use efficiency (WUE) and reduced the residual soil mineralizable N (Nmin) and apparent N losses. This study indicated that efficiency-enhanced management can significantly enhance the utilization efficiency of irrigation water and N fertilizers for cotton production in the fields of northwestern China. [ABSTRACT FROM AUTHOR]

A pot experiment was carried out with the following treatments: non-mycorrhizal control and inoculation by arbuscular mycorrhizal fungi (Glomus mosseae (Nicol. & Gerd.) Gerdemann & Trappe or Sclerocystis sinuosa Gerd. & Bakshi) at four P levels (0, 9.5, 19, and 38 mg P kg[sup -1]). Cotton (Gossypium arboreum L. cv. Xin-lu-zao No.l) was used as the host plant. The [sup 15]N-labeled urea (2.5% abundance) was mixed with soil thoroughly at a rate of 100mg Nkg[sup -1]. Colonization by the two arbuscular mycorrhizal fungi significantly improved the growth of cotton plants at all P levels compared with non-mycorrhizal plants. Nitrogen concentration in shoots was not significantly affected by arbuscular mycorrhizal fungi, while the nitrogen content was significantly higher in mycorrhizal plants than in non-mycorrhizal plants. The [sup 15]N atom % excess in mycorrhizal plant was significant lower than that in non-mycorrhizal plants. Considering the derivation of the nitrogen in the cotton plants, mycorrhizal fungi had no significant influence on uptake of nitrogen derived from fertilizer, but increased nitrogen derived from soil significantly. Colonization by mycorrhizal fungi increased the amount of soil available nitrogen ("A[sub N]" value). The results indicate that arbuscular mycorrhizal fungi may facilitated plant acquisition of nitrogen from sources which are not or less available to non-mycorrhizal plants. [ABSTRACT FROM AUTHOR]

Abstract To find the hyphal growth of cotton plants and its response to phosphorus (P) application under field conditions, a rhizobox method was used in a field experiment with different P fertilizer levels to collect the soil samples at different distances from the cotton root surface, and measured hyphal density, pH value and soil available P content distribution. We found that the hyphal growth range of cotton can extend to 30 mm from the root surface (under zero P addition), meaning that the cotton root increased its P absorption range by 15-fold under the hyphal growth. Within this range, the hyphal density was controlled by soil P content change. On the one hand, the hyphal extent decreased gradually away from the cotton roots with the increase of the soil available P content. On the other hand, a negative correlation was observed between the hyphal density and the soil available P content in different soil locations of distance away from the cotton root surface. We conclude that under a certain soil available P, the promotion or inhibition for hyphal growth was driven by soil available P change. Highlights • The maximum capacity of mycorrhizal hyphae for P uptake was distances of 3 cm from the cotton root in field conditions. • The root process showed a gradual decreasing influence on hyphal growth with the increase of distance from root surface. • The promotion or inhibition for hyphal growth was driven by soil available P change, caused by the cotton P absorption. [ABSTRACT FROM AUTHOR]

Although the root/mycorrhizal processes determine phosphorus (P) uptake by crops and P fertilizer use efficiency, knowledge of the plasticity of cotton root/mycorrhizal processes in response to changes in soil P content is lacking. A field experiment was conducted in 2015 and 2016 to investigate the effects of P fertilizer treatments (0, 75, 150, and 300 kg P 2 O 5 ha −1 ) on root/mycorrhizal processes and P uptake by cotton plants. The main aim was to explore the possibility of achieving high P fertilizer use efficiency and high yield simultaneously by optimization of P fertilizer application. A low P application rate (75 kg P 2 O 5 ha −1 ) not only increased root length and hyphal density simultaneously, but also enhanced the spatial distribution of cotton roots in the soil, thereby also increasing the apparent phosphorus recovery (APR). However, P uptake and cotton yield were highest under treatment with 150 kg P 2 O 5 ha −1 . Thus, it is difficult to maximize APR and cotton yield simultaneously. If the production target is to obtain a relatively high yield (80–90% of the highest potential yield), then root/mycorrhizal efficiency in P acquisition can be maximized through optimization of the soil available P content. The optimum soil available P content observed in this study was 15–20 mg kg −1 . [ABSTRACT FROM AUTHOR]