[Effects of different kinds of organic fertilizer on fruit yield, quality and nutrient uptake of watermelon in gravel-mulched field]. / ä¸åŒæœ‰æœºè‚¥å¯¹ç ‚ç”°è¥¿ç“œäº§é‡ã€å“è´¨å’Œå »åˆ†å¸æ”¶çš„å½±å“.

The effects of different kinds of organic fertilizer on the growth, yield, quality, and nutrient absorption and utlization of watermelon were examined to provide theoretical basis for adequate fertilization and efficient production of watermelon in gravel-mulched field in the Loess Pla-teau of Northwest China. The growth index and nutrient absorption at main stages of growth and development, yield and quality of watermelon were compared among treatments of applying chemical fertilizer (CK), cattle dung, chicken manure, sheep manure and pig manure which contained the equal amount of nitrogen, phosphorus and potassium. The results showed that vegetative growth index, nitrogen and potassium transportation were promoted, yield and nutrient accumulation were improved in treatments of cattle dung, chicken manure and pig manure. Compared to chemical fertilizer, the fruit yield increased by 27.4%, 31.6% and 30.2%, respectively, nitrogen accumulation improved by 26.3%, 39.8% and 47.4%, phosphorus accumulation increased by 49.3%, 48.3% and 55.9%, potassium accumulation improved by 35.8%, 41.6% and 51.9%, respectively, under cattle dung, chicken manure and pig manure treatments. The quality of watermelon was better in pig manure treatment among all the treatments. The central and edge sugar content of watermelon increased by 5.5% and 11.6%, respectively, and Vc content increased by 19.9%, compared with the chemical fertilizer treatment. There was no significant difference between sheep manure and chemical fertilizer treatments. In conclusion, chicken manure and pig manure were optimal organic fertilizers for watermelon planting in gravel-mulched field. The application of sheep manure should be avoided or reduced.

[Effects of grafting and nitrogen fertilization on melon yield and nitrogen uptake and utilization]. / å«æŽ¥ä¸Žæ–½æ°®å¯¹ç”œç“œäº§é‡å’Œæ°®ç´ å¸æ”¶ã€åˆ©ç”¨çš„å½±å“.

A split-field design experiment was carried out using two main methods of cultivation (grafting and self-rooted cultivation) and subplots with different nitrogen application levels (0, 120, 240, and 360 kg N·hm-2) to investigate the effects of cultivation method and nitrogen application levels on the yield and quality of melons, nitrogen transfer, nitrogen distribution, and nitrogen utilization rate. The results showed that melons produced by grafting cultivation had a 7.3% increase in yield and a 0.16%-3.28% decrease in soluble solid content, compared to those produced by self-rooted cultivation. The amount of nitrogen accumulated in melons grafted in the early growth phase was lower than that in self-rooted melons, and higher after fruiting. During harvest, nitrogen accumulation amount in grafted melon plants was 5.2% higher than that in self-rooted plants and nitrogen accumulation amount in fruits was 10.3% higher. Grafting cultivation increased the amount of nitrogen transfer from plants to fruits by 20.9% compared to self-rooted cultivation. Nitrogen distribution in fruits was >80% in grafted melons, whereas that in self-rooted melons was <80%. Under the same level of nitrogen fertilization, melons cultivated by grafting showed 1.3%-4.2% increase in nitrogen absorption and utilization rate, 2.73-5.56 kg·kg-1 increase in nitrogen agronomic efficiency, and 7.39-16.18 kg·kg-1 increase in nitrogen physiological efficiency, compared to self-rooted cultivation. On the basis of the combined perspective of commercial melon yield, and nitrogen absorption and utilization rate, an applied nitrogen amount of 240 kg·hm-2 is most suitable for graf-ting cultivation in this region.

[Distribution characteristics of soil aggregates and their associated organic carbon in gravel-mulched land with different cultivation years]. / ä¸åŒå¹´é™æ—±ç ‚ç”°åœŸå£¤å›¢èšä½“åŠå ¶æœ‰æœºç¢³åˆ†å¸ƒç‰¹å¾.

The distribution characteristics of soil aggregates and their organic carbon in gravel-mulched land with different planting years (5, 10, 15, 20 and 30 years) were studied based on a long-term field trial. The results showed that the soil aggregate fraction showed a fluctuation (down-up-down) trend with the decrease of soil aggregate size. The soil aggregates were distributed mainly in the size of ＞5 mm for less than 10 years cultivation, and 0.05-0.25 mm for more than 15 years. The content of aggregates over 0.25 mm (R0.25) and the mean weight diameter (MWD) of soil aggregates all decreased with the increase of cultivation time. The content of organic carbon within soil aggregates increased with the decrease of soil aggregate size in gravel-mulched land with diffe-rent planting years. However, the content of organic carbon within soil aggregates, contribution rates of different aggregate fractions to soil organic carbon and soil organic carbon storage of aggregate fractions decreased with planting time extension and soil depth. Soil organic carbon in the aggregate sizes over 1 mm was sensitive to long term gravel-mulched field planting. Organic carbon storage of aggregate fractions with 10, 15, 20 and 30 years of planting decreased by 8.0%, 24.4%, 27.5% and 31.4% in the soil depth of 0-10 cm, and 1.4%, 15.8%, 19.4% and 21.8% in the soil depth of 10-20 cm, respectively. In conclusion, the ability of soil carbon sequestration in arid gravel-mulched field was reduced with planting time extension. Therefore, soil fertility of gravel-mulched fields which were cultivated for more than 15 years need to be improved.

[Effects of nitrogen management on yield, quality, nitrogen accumulation and its transportation of watermelon in gravel-mulched field].

The effects of nitrogen management on yield, quality, nitrogen and dry matter accumulation and transportation of watermelon in sand field were studied based on a field experiment. The results showed that too low or too high basal nitrogen fertilzation was unfavorable to seedling growth of watermelon in sand field, and no nitrogen application at vine extension or fruiting stages limited the formation of 'source' or 'sink'. At the same nitrogen rate, compared with the traditional T1 treatment (30% basal N fertilizer + 70% N fertilizer in vine extension), the nitrogen and dry matter accumulation of vegetative organs of T4 treatment (30% basal N fertilizer + 30% N fertilizer in vine extension + 40% N fertilizer in fruiting) and T6 treatment (100% basal N fertilizer + NAM) were reduced significantly, but the nitrogen and dry matter accumulation of fruit were increased significantly in the flushing period. The nitrogen transportation ratio and nitrogen contribution ratio of T4 were 33.6% and 12.0%, respectively. Compared to T1, the nitrogen harvest index, nitrogen fertilizer partial factor productivity and nitrogen fertilizer recovery efficiency of T4 and T6 treatments increased by 14.1% and 12.7%, 11.6% and 12.5%, 5.3% and 8.7%, respectively, and yield of watermelon increased by 11.6% and 12.5%, the soluble sugar, effective acid, the ratio of sugar and acid, Vc content increased by 16.5% and 11.7%, 4.5% and 2.8%, 19.4% and 13.4%, 35.6% and 19.0%, respectively. Therefore, T4 and T6 treatments were the optimal nitrogen fertilizer management mode which could not only achieve high yield and quality but also obtain high nitrogen fertilizer use efficiency in sand field. T6 treatment was the best nitrogen fertilizer management mode considering reduction of fertilizing labor intensity and extending service time of gravel-mulched field.

[Interactive impact of water and nitrogen on yield, quality of watermelon and use of water and nitrogen in gravel-mulched field].

In order to develop the optimal coupling model of water and nitrogen of watermelon under limited irrigation in gravel-mulched field, a field experiment with split-plot design was conducted to study the effects of supplementary irrigation volume, nitrogen fertilization, and their interactions on the growth, yield, quality and water and nitrogen use efficiency of watermelon with 4 supplementary irrigation levels (W: 0, 35, 70, and 105 m³ · hm⁻²) in main plots and 3 nitrogen fertilization levels (N: 0, 120, and 200 kg N · hm⁻²) in sub-plots. The results showed that the photosynthetic rate, yield, and water and nitrogen use efficiency of watermelon increased with the increasing supplementary irrigation, but the nitrogen partial productivity and nitrogen use efficiency decreased with increasing nitrogen fertilization level. The photosynthetic rate and quality indicators increased with increasing nitrogen fertilization level as the nitrogen rate changed from 0 to 120 kg N · hm⁻², but no further significant increase as the nitrogen rate exceeded 120 kg · hm⁻². The interactive effects between water and nitrogen was significant for yield and water and nitrogen use efficiency of watermelon, supplementary irrigation volume was a key factor for the increase yield compared with the nitrogen fertilizer, and the yield reached the highest for the W70N200 and W105 N120 treatments, for which the yield increased by 42.4% and 40.4% compared to CK. Water use efficiency (WUE) was improved by supplementary irrigation and nitrogen rate, the WUE of all nitrogen fertilizer treatments were more than 26 kg · m⁻³ under supplemental irrigation levels 70 m³ · hm⁻² and 105 m³ · hm⁻². The nitrogen partial productivity and nitrogen use efficiency reached the highest in the treatment of W105N120. It was considered that under the experimental condition, 105 m³ · hm⁻² of supplementary irrigation plus 120 kg · hm⁻² of nitrogen fertilization was the optimal combination of obtaining the high yield and high efficiency.