[Effects of Balanced Fertilization and Straw Mulching on Soil Nutrients and Stoichiometry in Purple Soil Slope].

To explore the effects of long-term balanced fertilization and straw mulching on soil nutrients and stoichiometric ratios in purple soil sloping cropland, nine plots (length 7 m×width 3 m) were established in Dianjiang County as the research sample area of long-term farmland nitrogen and phosphorus loss monitoring. The following three treatments were set up:conventional mode (CK), balanced fertilization mode (M1), and balanced fertilization+straw mulching mode (M2), with three replications for each treatment to compare the contents of carbon (C), nitrogen (N), phosphorus (P), and potassium (K) and their stoichiometric changes under different treatments from 2018 to 2020. The results showed:K contents showed significant differences among the three treatments in 2018, in the order of CK>M2>M1. NO3--N and NH4+-N contents showed significant differences among the three treatments in 2019, both in the order of M1>M2>CK. Other nutrient contents showed no significant difference among different treatments each year. Soil C and N contents showed non-significant differences among different years. The total K contents of CK, M1, and M2 in 2018 were significantly higher than that in other years and were 78.26% and 98.79%, 19.13% and 35.4%, and 54.49% and 41.76% higher than that in 2019 and 2020, respectively. The total P content in the CK and M2 treatments decreased with years, and that of CK and M2 in 2018 was 20.29% and 10.67% and 39.68% and 17.33% higher than that in 2019 and 2020, respectively. The available potassium (AK) content of the three treatments showed non-significant differences among different years, whereas the contents of nitrate nitrogen (NO3--N), ammonium nitrogen (NH4+-N), and available phosphorus (AP) showed significant differences among the different treatments, with all being the highest in 2020. Soil C:P, C:K, N:P, N:K, and P:K ratios of each treatment showed significant differences among different years (P<0.05). Soil C:K, N:K, and AN:AP ratios all showed significant differences among different fertilization modes in 2018 and 2019, respectively (P<0.05). There was a significantly linearly positive relationship between soil C and N concentration and soil P and K concentration. There were very significant linear positive correlations between soil C:K and C:P, N:K, N:P, and P:K; N:K with C:P, P:K, and N:P; and N:P with C:P, N:P, and C:P. Soil P concentration was highly significantly linearly negatively correlated with C:K and N:K ratios. There were significant positive correlations between soil NO3--N, NH4+-N, AN:AP, and AN:AK; NH4+-N, AN:AP, and AN:AK; and AN:AP and AN:AK. The results suggested that balanced fertilization and straw mulching was a more suitable management mode for purple soil sloping cropland.

Combined effects of ramipril and angiotensin II receptor blocker TCV116 on rat congestive heart failure after myocardial infarction.

BACKGROUND: Congestive heart failure (CHF) is a major cause of morbidity and mortality worldwide and angiotensin converting-enzyme inhibitor (ACEI) is the cornerstone in its treatment. However, CHF continues to progress despite this therapy, perhaps because of production of angiotensin II (Ang II) by alternative pathways. The present study was conducted to examine the combined effects of a chronic ACEI, ramipril, and a chronic Ang II type 1 receptor blocker, TCV116, on rat CHF after myocardial infarction (MI). METHODS: Congestive heart failure was caused by MI in rats, which was induced by ligating the left anterior descending coronary artery. The experiment protocol included sham-operated rats (Sham), MI-control rats (MI-control), MI rats treated with ramipril 3 mg/kg (MI-ramipril) or TCV116 2 mg/kg (MI-TCV116) per day, half dosage (MI-1/2R&T) or full dosage (MI-R&T) combination of the two. At 22 weeks, cardiac hemodynamic parameters such as mean arterial pressure (MAP), left ventricular systolic pressure (LVSP), maximal rate of left ventricule pressure development and decline (LV dP/dtmax) and left ventricular end diastolic pressure (LVEDP), and cardiac morphometric parameters such as heart weight (HW), left ventricular weight (LVW) and left ventricular cavity area (LVCA) were measured, mRNA expressions of cardiac molecule genes such as beta myosin heavy chain (betaMHC), B-type natriuretic peptide (BNP), transforming growth factor-beta1 (TGF-beta1), collagen I and III were quantified with reverse transcription polymerase chain reaction (RT-PCR) in the surviving septum myocardium, and survival rates were calculated. RESULTS: There were no significant differences in MI sizes (%) among each MI related experimental groups (33 +/- 13, 34 +/- 14, 33 +/- 13, 35 +/- 13 and 33 +/- 14 for MI-control, MI-ramipril, MI-TCV116, MI-1/2R&T and MI-R&T, respectively, no statistical significance for all). Compared with sham-operated rats, MI rats without therapy showed significant increases in morphometric parameters as well as in mRNA expressions of cardiac molecule genes (P < 0.01); while their hemodynamic parameters were significantly impaired (P < 0.01), and in terms of spontaneous deaths survival rate shortened (P < 0.05). Compared with MI rats without therapy, MI rats treated with each single drug showed significant attenuation of mRNA expressions of cardiac molecule genes (P < 0.01); while their hemodynamic parameters were significantly improved (P < 0.05 or P < 0.01), and in terms of spontaneous deaths survival rate prolonged (P < 0.05). Both half and full dosage combined treatments exerted more powerful effects on improvement of cardiac phenotypic changes and on attenuation of betaMHC, BNP mRNA expressions (P < 0.05 vs monotherapy); while LVEDP was further lowered (P < 0.05 vs monotherapy). However, the total death in MI rats with full dosage combined treatment was more though there were no significant differences when compared with other treatments. CONCLUSIONS: The results suggest that treatment with appropriate dosage combination of a chronic ACEI and a chronic ARB may further improve cardiac remodeling and cardiac function after MI.