Sweet potato varieties exhibited distinct feedback mechanisms in response to continuous cropping obstacles (CCO). This study evaluated the tolerance to CCO (TCCO) among three types (fresh, purple, and starch), each comprising five varieties, cultivated in a 16-year CCO plot (CCp) and adjacent non-continuous cropping plots (NCCp) in China. Yield, resistance coefficient (k_Y, yield ratio between CCp and NCCp), and nitrogen (N), phosphorus (P), and potassium (K) contents and relative accumulation (k_N, k_P, k_K, similar to k_Y) in chunks or stem vines, were analyzed. Significant differences (p<0.05) in yield and nutrient contents were observed among all varieties and types. Four varieties (purple: Xu A1-144, Xu D9-123, and starch: Shang 19, Zhe 13) exhibited k_Y>1.0, indicating higher yields under CCp. Nutrient imbalance—particularly enhanced N uptake, was associated with CCO susceptibility. Fresh and purple chunks preferentially accumulated N, P and K, respectively, while starch varieties plants strongly absorbed more K. Under NCCp, chunks nutrient levels were correlated with multiple elements in stem vines. Under CCp, each chunk nutrient was primarily affected only by its homologous elements in stem vines. Notably, stem vine k_K positively correlated with yield under CCO (r=0.34, p<0.05), and stem vines k_N significantly correlated with both chunks k_N and stem vines k_K (p<0.05). Starch sweet potatoes demonstrated the most balanced NPK absorption for TCCO, with yield and nutrient absorption advantages. TCCO was closely linked to efficient and coordinated N–K absorption, regulated by genetic traits and soil nutrient status. Imbalanced NPK ratios and hindered K absorption played a central role in CCO. Strategies focusing on K management and breeding varieties with inter-organ nutrient coordination abilities could enhance the stress resistance of sweet potato production systems. These findings provide genetic resources and insight into the mechanism of CCO tolerance in sweet potato.

Good growth of tomato at the early growing stages is the key to final yield formation, for which water (W) and nitrogen (N) applications are two necessary factors. In this study, two irrigating systems (W1, W2) and three N applications (N1, N2, N3) were interacted (W×N) to plant the cherry tomato variety “Jinling Meiyu” in greenhouse. W1 (reduced irrigation) and W2 (normal irrigation) had a 7:9 irrigated ratio based on former research. N1, N2, and N3 were set at 100%, 80%, and 60% normal N application, respectively. The tomato plant height (PH), stem circumference (SC), number of leaves (NL), number of first order fruits (NF), the single fruit weight (SFW), contents of fruit Vitamin C (VC) and soluble sugar (SS), fresh weights of root (RW), leaf (LW), and plant stem (PSW), as well as leaf chlorophyll fluorescence value (SPAD), temperature (T), humidity (RH), and nitrogen content (N) were investigated at the first flowering and fruiting stage. The results showed that W×N had significant impacts on early plant growth and fruit quality of tomato. W2N2 obviously received the largest values of tomato PH (152.5 cm), SC (4.1 cm), NF (11 fruits/plant), and LW (45.0 g/plant), but obtained the lowest VC (9.71 mg/kg) and SS (2.40%). However, W1N3 had the largest values of leaf RH (56.9%), N contents (14.23 mg/g), and VC (16.29 mg/kg), with NF also at 11.0 fruits/plant. W2N1 significantly had the highest RW (14.4 g/plant), PSW (71.8 g/plant), and SFW (21.3 g/fruit). W2N3, W1N1, and W1N2 obtained the most NL (103.7 pieces/plant), SS (4.06%), and leaf SPAD (36.85), respectively. Pearson correlation analysis results showed PH negatively significantly correlated with NF (p<0.05). The leaf SPAD positively significantly correlated with PH (p<0.05) and RH (p<0.01), but negatively significantly correlated with SC (p<0.05) and T (p<0.01). Moreover, leaf N content also had a positive significant correlation with PH (p<0.05), and an extremely positive significant correlation with RH and SPAD (p<0.01). However, it negatively significantly correlated with SC (p<0.01) and T (p<0.05). Significantly, VC had positive correlations with PSW, leaf SPAD, and N content (p<0.05). SS negatively correlated with PSW (p<0.05) and T (p<0.01), and extremely significantly positively correlated with SPAD (p<0.01). Additionally, RW had an extremely significant relationship with PSW (p<0.01). Two-factor analysis of variances showed W extremely significantly influenced leaf T, RH, SPAD, and N content (p<0.001), as well as SC (p<0.01) and SS (p<0.05). Meanwhile, N management extremely significantly influenced LW (p<0.001), RW (p<0.01), and leaf T (p<0.05). However, W×N obviously significantly influenced just PSW (p<0.01), RW (p<0.001), and VC (p<0.05). Taking all factors into account, the early reasonable W×N management could promote growth of tomato plants and fruit quality at the first fruiting and ripening stage. These results could provide a foundation for the subsequent growth of tomato fruits and could also be beneficial for the precise management of greenhouse tomatoes at the early growing stages.