Seed germination plays important roles in the establishment of seedlings and their subsequent growth; however, seed germination is inhibited by salinity, and the inhibitory mechanism remains elusive. Our results indicate that NaCl treatment inhibits rice seed germination by decreasing the contents of bioactive gibberellins (GAs), such as GA1 and GA4, and that this inhibition can be rescued by exogenous bioactive GA application. To explore the mechanism of bioactive GA deficiency, the effect of NaCl on GA metabolic gene expression was investigated, revealing that expression of both GA biosynthetic genes and GA-inactivated genes was up-regulated by NaCl treatment. These results suggest that NaCl-induced bioactive GA deficiency is caused by up-regulated expression of GA-inactivated genes, and the up-regulated expression of GA biosynthetic genes might be a consequence of negative feedback regulation of the bioactive GA deficiency. Moreover, we provide evidence that NaCl-induced bioactive GA deficiency inhibits rice seed germination by decreasing α-amylase activity via down-regulation of α-amylase gene expression. Additionally, exogenous bioactive GA rescues NaCl-inhibited seed germination by enhancing α-amylase activity. Thus, NaCl treatment reduces bioactive GA content through promotion of bioactive GA inactivation, which in turn inhibits rice seed germination by decreasing α-amylase activity via down-regulation of α-amylase gene expression.
The practice of smash-ridging on dry land crop cultivation has shown much promise. However, the mechanism how does soil functionality and root traits can affect rice yield under smash ridge tillage with reduced nitrogen fertilization have not yet been explored. To fill this knowledge gap, we used three tillage methods—smash-ridging 40 cm (S40), smash-ridging 20 cm (S20), and traditional turn-over plowing 20 cm (T)—and two rice varieties (hybrid rice and conventional rice) and measured soil quality, root traits, rice yield and their correlation analysis at different growth stages. Soil physical and chemical properties were significantly improved by smash-ridging, including improvements in root morphological and physiological traits during three growth stages compared with T. S40 had the highest leaf area index (LAI), plant height (PH), and biomass accumulation (BA). Increment in biomass and panicle number (PN) resulted in higher grain yield (GY) of 6.9–9.4% compared with T. Correlation analysis revealed that root total absorption area (RTAA), root active absorption area (RAA), and root area ratio (RAR) were strongly correlated with soil quality. Root injury flow (RIF) and root biomass accumulation (RBA) were strongly correlated with LAI and above-ground plant biomass accumulation (AGBA). Conclusively, S40 is a promising option for improving soil quality, root traits, and consequently GY.
Conventional tillage (CT) is the main agricultural practice for rainfed sugarcane production in China. However, subsoil compaction formed by long-term CT is harmful to soil properties and crop yield. Deep vertical rotary tillage (DVRT) is a novel tillage practice, which can alleviate subsoil compaction and create a more favorable soil environment for crop growth. This study aims to compare the effects of DVRT and CT practices on soil properties and sugarcane characteristics. The results showed that DVRT reduced soil bulk density and increased soil porosity to some extent in the 0–40 cm soil profile. Soil water storage of DVRT was relatively higher compared with CT due to the combined effects of soil water holding capacity and vegetation water consumption. There was significantly higher final aboveground biomass, underground biomass, and plant height from DVRT compared to CT (p < 0.05), but there were no differences in final root length between tillage practices. Compared with CT, DVRT with one and two growth-years significantly increased aboveground biomass by 68.90% and 50.14%, respectively. Generally, the soil properties and sugarcane characteristics were not significantly different between DVRT with different growth years. DVRT is recommended as a tillage practice for sustainable agriculture in rainfed regions.
Core Ideas Compared with no tillage and subsoiling, deep vertical rotary tillage significantly increased grain yield of densely planted summer maize. Compared with no tillage, subsoiling and deep vertical rotary tillage significantly increased N use efficiency of densely planted summer maize. The T × N interaction showed that the grain yield of T3–N225 was the highest; however, T3–N150 or T2–N225 has better N use efficiency In light of the economic benefits, the optimal cultivation practice was deep vertical rotary tillage with N rate of 225 kg ha–1. Long periods of single tillage practice combined with excessive nitrogen (N) application are major factors restricting high yield and high efficiency production in the North China Plain. Field experiments were conducted by using a split‐plot design. Main plots included three different tillage practices: no tillage (T1), subsoiling tillage (T2), and deep vertical rotary tillage (T3). Subplots consisted of four different N application rates (N300: 300 kg ha−1; N225: 225 kg ha−1; N150: 150 kg ha−1; N0: 0 kg ha−1) with a plant density of 90,000 plants ha−1. Under the same N rate, T3 increased grain yield by 19.1 and 13.4% compared with that of T1 and T2. Under the same tillage practice, grain yield decreased with the reduced N rate, but the difference between N225 and N300 was not significant in most cases. Nitrogen agronomic efficiency (AEN), N recovery efficiency (REN), and partial factor productivity of applied N (PFPN) of T3 and T2 were higher than that of T1. Compared with T1, T2 increased AEN, REN, and PFPN by 6.5, 139.2, 6.1%, respectively, and T3 increased AEN, REN, and PFPN by 36.2, 82.1, and 20.1%, respectively. Levels of AEN, REN, and PFPN reduced with increasing N application rate in 2016, but N225 has the highest AEN and REN in 2017. The T × N interaction showed that the grain yield of T3–N225 was the highest; however, T3–N150 (2016) and T2–N225 (2017) had the highest AEN and REN. In light of the economic benefit, the optimal management strategy was 225 kg N ha−1 paired with deep vertical rotary tillage.
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