Effects of different fertilizers on nutrient quality and mineral elements in different economic forage groups in Qilian Mountain alpine meadows.

The objective of this study was to examine the responses of nutrient quality and mineral elements of forages in different economic groups forages in the Qilian Mountains alpine meadows to different fertilization treatments. Eight fertilization treatments, potassium (K), nitrogen (N), zinc (Z), boric (B), copper (Cu), phosphorus (P), molybdenum (Mo), and selenium (Se), were sprayed onto forage roots, and no fertilizer was applied as a blank control (CK), with four replicates in each group. The forage trace element contents and nutritional quality of each economic group in to different treatments were determined in mid-August, and the trace element surplus and deficiency were analyzed. Compared with that in the control, the forage crude protein (CP) content in different economic groups under different fertilization treatments increased and fluctuated within the range of 7.7%-23.94%. The dry matter digestibility (DMD) ranged from 38.78% to 77.34% and showed no significant differences in DMD among treatments (P > 0.05). The DMD of legume forages was significantly higher than those of Gramineae grasses and sedges; there were no significant differences in forage acid detergent fiber (ADF) between any treatments and the control (P > 0.05), but ADF showed a decreasing trend in the treatments compared with that in the control. The P content increased by 81.81% in legumes (P < 0.05); however, it decreased by 38.46% and 61.29% in wilted grass and forbs (P < 0.05) and increased in Gramineae grasses and legumes under N treatment by 92.86% and 50% (P < 0.05), respectively. The Cu content under Cu, N, Zn, B and Se treatments increased significantly by 33.81%∼346.49% compared with that in the control. There were no significant differences in Zn content among the economic groups under different treatments (P > 0.05), but legumes showed better absorption of Zn. Consequently, the forages in this study were evaluated as having medium Cu (8.1-20 mg/kg), medium Se (0.11-1.0 mg/kg), and medium (30.1-60 mg/kg) to high (60.1-100 mg/kg) Zn contents. Comprehensive analysis showed that the application of different fertilizers could increase the CP and DMD of various forages, reduce ADF, and effectively improve the nutritional quality of pastures. The contents of N, Cu, Zn, and Se in forages increased under all treatments, and the contents of all forage elements were at appropriate levels. Applying K, N, P, Cu and Mo is beneficial to dominant species in Qilian Mountains alpine meadows.

Appropriate Reference Genes for RT-qPCR Normalization in Various Organs of Anemone flaccida Fr. Schmidt at Different Growing Stages.

Anemone flaccida Fr. Schmidt is a traditional medicinal herb in southwestern China and has multiple pharmacological effects on bruise injuries and rheumatoid arthritis (RA). A new drug with a good curative effect on RA has recently been developed from the extract of A. flaccida rhizomes, of which the main medicinal ingredients are triterpenoid saponins. Due to excessive exploitation, the wild population has been scarce and endangered in a few of its natural habitats and research on the cultivation of the plant commenced. Studies on the gene expressions related to the biosynthesis of triterpenoid saponins are not only helpful for understanding the effects of environmental factors on the medicinal ingredient accumulations but also necessary for monitoring the herb quality of the cultivated plants. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) as a sensitive and powerful technique has been widely used to detect gene expression across tissues in plants at different stages; however, its accuracy and reliability depend largely on the reference gene selection. In this study, the expressions of 10 candidate reference genes were evaluated in various organs of the wild and cultivated plants at different stages, using the algorithms of geNorm, NormFinder and BestKeeper, respectively. The purpose of this study was to identify the suitable reference genes for RT-qPCR detection in A. flaccida. The results showed that two reference genes were sufficient for RT-qPCR data normalization in A. flaccida. PUBQ and ETIF1a can be used as suitable reference genes in most organs at various stages because of their expression stabilitywhereas the PUBQ and EF1Α genes were desirable in the rhizomes of the plant at the vegetative stage.

Correction: Identification of soil P fractions that are associated with P loss from surface runoff under various cropping systems and fertilizer rates on sloped farmland.

[This corrects the article DOI: 10.1371/journal.pone.0179275.].

Identification of soil P fractions that are associated with P loss from surface runoff under various cropping systems and fertilizer rates on sloped farmland.

Soil phosphorus (P) fractions and runoff P concentration were measured to understand the fate of soil P entering surface runoff water during summer cropping season of different double cropping systems under two fertilizer regimes. The dominant form of runoff P was particulate P (PP). Runoff total P (TP) was higher at the vegetative growth stage and lower at the crop reproductive stage. TP and PP were derived mainly from soil Olsen-P, Al-P and Fe-P and amounts increased with sediment content in runoff water. Runoff P discharge was closely related to the changes in soil P forms. Soil Olsen-P, mainly consisting of some Ca2-P and Al-P, was increased by elevating fertilizer rate. Along with crop growth, there were active interconversions among Olsen-P, Org-P, Fe-P and O-Al-P in the soil, and some available P converted into Ca10-P, with O-Fe-P possibly being a transitional form for this conversion. The oilseed rape/corn system had less runoff TP at the early stage, and wheat/sweet potato system had a lower runoff P at the late stage. Intercropping corn with sweet potato in the field with oilseed rape as a previous crop may be helpful for alleviating runoff P load during the summer in this region.

Phosphorus and Defoliation Interact and Improve the Growth and Composition of the Plant Community and Soil Properties in an Alpine Pasture of Qinghai-Tibet Plateau.

Pasture degradation caused by overgrazing and inappropriate fertiliser management is a major production and environmental threat in Qinghai-Tibet Plateau. Previous research has focused on the effects of mixed nitrogen (N) and phosphorus (P) fertiliser and reduced grazing pressure on the plant community of the grassland; however, the role of P and how it interacts with various defoliation (the process of the complete or partial removal of the above-ground parts of plants by grazing or cutting) intensities on the plant and soil of the grassland ecosystem have not been quantified. A field experiment was conducted to quantify how P application in combination of defoliation pressure could impact the dynamic change of the plant and soil in a native alpine grassland ecosystem of the Qinghai-Tibet Plateau, China, from May 2012 to September 2014. A split-plot design with 4 replicates and repeated measures was used to determine the growth and composition of plant community and soil physical and chemical properties under various levels of P fertiliser and defoliation intensity. The results showed that applying 20 kg P/ha increased the herbage yield of Melissitus ruthenica by 68% and total pasture yield by 25%. Close defoliation favoured the growth and plant frequency of the shorter species, whereas lax defoliation favoured that of the taller plant species. Medium P rate and cutting to 3 cm above ground gave an overall best outcome in pasture yield, quality and frequency and soil moisture and nutrient concentration. Application of P fertiliser with a moderate defoliation pressure to promote legume growth and N fixation has the potential to achieve multiple benefits in increasing pasture and livestock production and improving environmental sustainability in the alpine pasture of Qinghai-Tibet Plateau, a fragile and P-deficient ecosystem zone in China and its western neighbouring countries.