Hybrid rice yield response to potted-seedling machine transplanting and slow-release nitrogen fertilizer application combined with urea topdressing

Machine transplanting and the application of slow-release nitrogen(N) fertilizer(SRNF) have played vital roles in the modernization of rice production. We aimed to determine the effects of potted-seedling transplanting—a new machine-transplanting method—and SRNF on hybrid rice yields. A 2-year splitplot experiment(2016–2017) was conducted in Meishan, Sichuan province, China, using two machinetransplanting methods(potted-seedling and blanket-seedling) and three N treatments. Total green leaf area, high-effective leaf area and its rate at heading, net photosynthetic rate of flag leaves 7 days after heading, glutamate synthase(GOGAT) and glutamine synthase(GS) activity after heading, dry matter production, and N accumulation at heading and maturity increased under the potted-seedling method or 70% SRNF as a base + 30% urea application at the panicle initiation stage(SBUP). Stem diameter and number of small and of all vascular bundles at the neck–panicle node in potted-seedling plants increased as a result of increasing numbers of effective panicles, secondary branches, and spikelets. In pottedseedling plants, treatment with SBUP increased the number of large and total vascular bundles at the panicle–neck internode and the number of differentiated and surviving secondary branches and spikelets and decreased the number of ineffective tillers and degenerated secondary branches and spikelets. We conclude that the potted-seedling machine transplanting method and SRNF combined with urea topdressing can strengthen the source–sink relationship in rice, resulting in higher yields.

Study on Cotton Nitrogen Diagnosis and Topdressing Recommendation in North Xinjiang,China

Field experiments were conducted to study cotton nitrogen diagnosis and topdressing recommendation by measuring cotton tissue NO3- concentration with Reflectoquant. Results showed that the order of NO3- concentration in different cotton plant tissues is petiole > stem > leaf, and upper parts> lower parts. There was significant change in each growth period, which was, NO3- concentration in budding-blooming period was the highest whereas it was the lowest in full blooming period. NO3- concentration in the 4th expanding petiole is relatively stable and can sensitively indicate cotton nitrogen state so it was chosen as diagnosis tissue. NO3- content in budding-blooming period was significantly correlated with seed-cotton yield so it was chosen as diagnosis period. Primary cotton's nitrogen diagnosis index and amount of topdressing was formulated by regression of NO3- concentration against seed-cotton yield. It was not only rapid and accurate but also time-saving and flexible by using Reflectoquant to diagnose cotton nitrogen states and make side-dressing recommendation , so it is an agricultural technique with promising prospect.

Effects of Delayed Nitrogen Topdressing on Grain Yield and Photosynthetic Characteristics of Flag Leaves of Wheat

Four wheat cultivars were used to study the effects of delayed nitrogen topdressing on population structure, grain yield and photosynthetic characteristics of flag leaves under high-yielding conditions. The results showed that the nitrogen topdressing delayed from overwintering-turning green stage (N1) to turning green-jointing stage(N2) and jointing-booting stage(N3) decreased ineffective tiller in spring, retarded the decline of green leaf area and chlorophyll content in late life span, promoted photosynthetic ability of flag leaves and significantly increased the grain yield. N3 treatment was suitable for most wheat cultivars except the genotypes with higher single spike productivity and less ears in unit area.

Effect of Nitrogen Topdressing on Growth and Yield of Garlic

With Cangshan garlic and early bolting garlic as experimental materials,this paper studies the effect of nitrogen topdressing on the garlic growth and yield of garlic stems and garlic bulbs. The results show that under the same amount of nitrogen,applying ammonium phosphor nitrate can better promote the growth of garlic than applying urea and ammonium chloride; both ammonium chloride and ammonium phosphor nitrate can effectively improve the yield of garlic stems and garlic bulbs,especially for ammonium phosphor nitrate; through economic benefit analysis,applying ammonium chloride and ammonium phosphor nitrate can produce greater economic benefits than applying urea,and especially ammonium phosphor nitrate increases the economic benefits of Cangshan garlic and early bolting garlic by 5490 yuan and 6690 yuan per ha,respectively.

Effects of topdressing ratio and frequency on the dry matter, yield, and quality of tomato and celery under a small amount of continuous subsurface drip irrigation

Compared with conventional full irrigation,the existing water-saving irrigation method achieves the purpose of water saving by actively controlling soil moisture.High-frequency irrigation can make the ideal conditions for soil water movement and root absorption of water and nutrients.This research used a plot experiment in a greenhouse and set up different fertilization amounts and frequencies during the growth stage to study the effects of small-amount and continuous subsurface drip irrigation on the dry matter,yield,and quality of tomato and celery.The results showed that the frequency of topdressing had a great influence on the dry matter accumulation of tomatoes,and the amount of topdressing had little effect on the fresh weight of the upper part of a tomato plant.The application of high-frequency fertilizer increased the dry matter accumulation in the underground part of the tomato.Under the premise given amount of total fertilization,the growth rate and yield of tomatoes were positively correlated with the amount of topdressing.The optimum fertilization frequency was 1 time during the first fruit stage,3 times for the second fruit stage,and 5 times for the third fruit stage,the yield during the fourth stage was increased with higher frequency,and the topdressing was started ahead of the fourth fruit stage when the diameter of fruit was 40 mm.The lower fertilization frequency during the early stage and higher fertilization frequency during the later stage can increase the yield of celery.The higher ratio of topdressing,the higher frequency during the early growth stage,and the lower frequency during the later stage can achieve the best quality of celery.

Suitability of the DNDC model to simulate yield production and nitrogen uptake for maize and soybean intercropping in the North China Plain

Intercropping is an important agronomic practice. However, assessment of intercropping systems using field experiments is often limited by time and cost. In this study, the suitability of using the DeNitrification DeComposition(DNDC) model to simulate intercropping of maize(Zea mays L.) and soybean(Glycine max L.) and its aftereffect on the succeeding wheat(Triticum aestivum L.) crop was tested in the North China Plain. First, the model was calibrated and corroborated to simulate crop yield and nitrogen(N) uptake based on a field experiment with a typical double cropping system. With a wheat crop in winter, the experiment included five treatments in summer: maize monoculture, soybean monoculture, intercropping of maize and soybean with no N topdressing to maize(N0), intercropping of maize and soybean with 75 kg N ha–1topdressing to maize(N75), and intercropping of maize and soybean with 180 kg N ha–1topdressing to maize(N180). All treatments had 45 kg N ha–1as basal fertilizer. After calibration and corroboration, DNDC was used to simulate long-term(1955 to 2012) treatment effects on yield. Results showed that DNDC could stringently capture the yield and N uptake of the intercropping system under all N management scenarios, though it tended to underestimate wheat yield and N uptake under N0 and N75. Long-term simulation results showed that N75 led to the highest maize and soybean yields per unit planting area among all treatments, increasing maize yield by 59% and soybean yield by 24%, resulting in a land utilization rate 42% higher than monoculture. The results suggest a high potential to promote soybean production by intercropping soybean with maize in the North China Plain, which will help to meet the large national demand for soybean.

Timing of N Application Affects Net Primary Production of Soybean with Different Planting Densities

Understanding the relationship between the timing of N fertilizer applications and crop primary production is crucial for achieving high yield and N use efifciency in agriculture. This study investigated the effects of starting-N plus topdressing N applications （as compared to the common practice of all basal application） on soybean photosynthetic capacity under different planting densities. A ifeld experiment was conducted in two growing seasons （2011 and 2012）, and the soybean （Glycine max L. Merrill） cultivar was Dongnong 52, three planting densities （20, 25 and 30 plants m-2）, and four N fertilizer application patterns （all N fertilizer of 6 g N m-2 as basal fertilizer, all N fertilizer as topdressing at beginning pod stage （R3）, 1.8 g N m-2 as basal fertilizer and 4.2 g N m-2 as topdressing at stage R3 and full pod stage （R4）, respectively）. The results indicated that under the same planting density, compared to applying all N as basal fertilizer, the application of starter-N plus topdressing N substantially reduced the rate of pod abscission, and enhanced leaf area index （LAI） signiifcantly at beginning seed stage （R5） （P〈0.05）, net assimilation rate （NAR） during stages R4-full seed stage （R6） （P〈0.05）, contribution rate of post-seed iflling assimilate to seed （CPA） （P〈0.05）, and yield （P〈0.05）. Applying topdressing N at stage R4 resulted in higher net primary production and yield than applying topdressing N at stage R3. When applying starter-N plus topdressing N at planting density of 25 plants m-2, LAI after stage R5 and NAR after stage R4 were increased by 5.92-16.3%（P〈0.05） and 13.7-26.6%（P〈0.05） with the planting density of 20 plants m-2, respectively, and yield was 8.46-14.0%（P〈0.05） higher than that under 20 plants m-2. When planting density increased to 30 plants m-2, only LAI during stages R4-R5 and NAR during stages R4-R5 increased by applying starter-N plus topdressing N, while the other indexes declined. Overall, results of this study demonstrated that applying starter-N plus topdressing N could signiifcantly enhance soybean photosynthetic capacity after stage R5 at planting density of 25 plants m-2.

Application Effect of Integrated Water and Fertilizer Technology for Tomato

Integrated water and fertilizer technology has the advantages of saving water,fertilizer and labour,which is widely applied in tomato plantation. Integrated water and fertilizer technology in topdressing and whole process of big and small tomatoes were studied,and their application effects were contrasted and analyzed,and application advantages and scopes of the two models were concluded.