【Objective】 This paper mainly studied the dynamic changes of soil N2O emission and the activities of urease (UR), nitrate reductase (NR), nitrite reductase (Ni R) and hydroxylamine reductase (Hy R) under the condition of drip irrigation water and fertilizer integration by applying different amounts of inorganic nitrogen to organic nitrogen, and analyzed the soil N2O emission characteristics of every treatment and the effects of soil UR, NR, Ni R and Hy R activities on soil N2O emissions, the purpose of this research was to reveal the influence mechanism of N2O emission process under the integration of drip irrigation water and fertilizer.【Method】 The treatments consisted of CK (no nitrogen application), N1 (200 kg·hm -2 organic nitrogen), N2 (200 kg·hm -2organic nitrogen + 250 kg·hm -2 inorganic nitrogen), and N3 (200 kg·hm -2 organic nitrogen + 475 kg·hm -2inorganic nitrogen). Using static-chamber method, the soil N2O emission, enzyme activity, soil temperature and humidity during the growth period of tomato were monitored.【Result】 The integration of water and fertilizer in drip irrigation showed that the N2O emission peak of every treatment appeared at the first day after fertilization + irrigation, and decreased continuously with the passage of time. The N2O emission flux range under different treatments was 0.98-1544.79 μg·m -2·h -1. The total N2O emissions during the growth period of tomato under different treatments had significant differences among each treatment, which were N3 ((7.13±0.11) kg·hm -2) >N2 ((4.87±0.21) kg·hm -2) >N1 ((2.54±0.17) kg·hm -2) >CK ((1.56±0.23) kg·hm -2). Compared with N3, the total soil N2O emissions from N1 and N2 decreased by 64.38% and 31.70%, respectively. During the growth period of tomato, the characteristics of seasonal emission of N2O changed obviously, which revealed high in autumn and low in winter. The activity of soil nitrogen-related enzymes increased with the increase of nitrogen application rate. The soil N2O flux was positively correlated with 5 cm soil temperature, 0-10 cm soil nitrate nitrogen content, soil NR activity and soil Hy R activity (P＜0.01).【Conclusion】 Under the integration of drip irrigation and water and fertilizer, soil N2O mainly came from the nitrification process, which reduced the N2O emissions generated by the denitrification process. Considering the factors such as tomato yield, quality and N2O emission, it was recommended to apply 200 kg·hm -2organic nitrogen +250 kg·hm -2 inorganic nitrogen, 75 kg·hm -2 P2O5 and 450 kg·hm -2 K2O in northern greenhouse autumn-winter tomato.
【Objective】 Under the condition of replacing the inorganic fertilizer part with the same amount of nitrogen, the purpose of this study was to study the emission characteristics of greenhouse tomato soil N2O and to explore the environmental factors affecting N2O emissions, which could provide data support and theoretical basis for the N2O emission inventory of the greenhouse vegetable system and its emission reduction potential.【Method】 Taking greenhouse autumn-winter tomato as the research object, the static-chamber method was used to monitor the soil N2O emission, soil temperature and soil water content during the growth period of tomato. The experiment was set 4 treatments, including non-fertilization (CK), single application of organic fertilizer (MN), single application of inorganic fertilizer (CN), and organic partial replacement of inorganic fertilizers (CMN).【Result】 Under the same nitrogen application rate, the total N2O emission under CMN was 4.05 kg·hm -2. Compared with CN and MN, the total N2O emission under CMN decreased by 45.1% and 33.2% , respectively; the emission factor of soil N2O was reduced by 50.0% and 37.5%, respectively; the emission intensity was reduced by 50.0% and 42.1%, respectively. The peak soil N2O of all treated appeared on the first day after fertilization and irrigation, and the discharge was mainly concentrated within 5 days after fertilization and irrigation. The N2O emission flux in greenhouse tomato soil showed significant or extremely significant correlation with the ground temperature of 0-5 cm soil, and showed a significant or extremely significant logarithm function relationship with soil water-filled porosity (WFPS). The peak of soil N2O emission under different fertilization treatments appeared in 60%~80% soil-filled porosity.【Conclusion】 The relationship between the growth and decline of N2O emissions in greenhouse tomato soil was reflected in the changes of temperature and humidity and the type of nitrogen fertilizer input. Reasonable emission reduction measures should be considered based on the above factors. Partial replacement of inorganic fertilizers with organic fertilizers was an important means to increase greenhouse tomato production, to reduce N2O emissions intensity, factor and total N2O emissions increase fertilizer utilization, and to achieve zero growth of fertilizers.
【Objective】 Aiming at the problem of phosphorous accumulation in greenhouse soil, the effects of applying chicken manure and phosphorus fertilizer on phosphorus accumulation in soil under drip irrigation were studied.【Method】 The solar greenhouse in North China Plain using drip irrigation was taken as research object. Five treatments were designed, including no fertilizer (CK), single phosphate (P1), single chicken manure (OM), chicken manure and reduced phosphate fertilization (OM+P1), chicken manure and habitual phosphate fertilization (OM+P2), to reveal the enrichment and transformation, migration and distribution in vertical section of soil at different growth stages and availability of inorganic phosphate form in soil.【Result】 The results showed that the combination of chicken manure and phosphate fertilizer significantly increased the accumulation and residue of total phosphorus, available phosphorus (Olsen-P) and inorganic phosphorus in soil. In the soil layer of 0-20 cm, total phosphorus content decreased with the development of cucumber growth period, highest in seeding stage and lowest in late fruiting stage period. Under different fertilization treatments, total phosphorus contents were significantly different, and the sequence of each growth period was OM+P2 treatment>OM+P1 treatment>P1 treatment>OM treatment>CK treatment. The Olsen-P contents at different levels in the soil profile varied greatly. In seedling stage, the range was 44.43-86.08 mg·kg -1 at soil of 0-20 cm, 6.51-10.05 mg·kg -1 at soil of 20-40 cm, and there was very little variability in soil layer lower than 40 cm. The effect of water on the movement of phosphorus was slight under the condition of drip irrigation in greenhouse. So Olsen-P mainly concentrated in the soil layer of 0-20 cm, which accounted for 68.76-87.78% of the available phosphorus in soil profile of 0-100 cm in each growth period. Compared with CK, the other treatments increased the proportion of Olsen-P in total phosphorus by 1.23%-2.47%. The sequence of inorganic phosphorus content of different forms in soil layer of 0-20 cm was Ca10-P>Ca8-P>O-P>Ca2-P>Al-P>Fe-P, among which, the proportion of Ca-P was the highest (79.55%-83.35%). As the amount of phosphorus fertilizer increased, so did the accumulation of phosphorus. The contents of Ca8-P, Ca2-P, Al-P, Fe-P and Ca10-P under fertilization treatments were all significantly higher than that under CK, with Ca8-P increased the most, followed sequentially by Ca2-P, Al-P and Fe-P. Phosphate fertilizer would be converted into Ca8-P through Ca2-P soon after it was applied into the soil, which accumulated in the soil in a slow manner. Among all forms of inorganic phosphorus, Ca8-P accumulated the most, Al-P and Fe-P also accumulated to a certain extent.【Conclusion】 Traditional excessive fertilization caused phosphorus remaining in the soil in the forms of Ca8-P, Al-P and Fe-P, resulting in the accumulation of soil phosphorus and waste of phosphorus fertilizer. On the basis of 30,000 kg·hm -2 chicken manure, adding phosphate fertilizer had no significant effect on increasing yield but obviously increased the residual accumulation of phosphorus. If only chicken manure was applied, the dosage should not exceed 30 000 kg·hm -2. If inorganic phosphate fertilizer was combined, the amount of chicken manure should be reduced, while the inorganic phosphate fertilizer rate should be less than 300 kg·hm -2. The specific amount and proportion of fertilizer application need further study and discussion.
【Objective】 This study focused on determining the appropriate soil water parameters and the potential of soil nitrogen supply at different growth stages of drip irrigated cucumber to optimize the water and fertilizer management and to guarantee the sustainable green and high yield production.【Method】 A plot experiment was conducted inside a greenhouse using cucumber as tested material during the winter-spring growing season. Drip irrigation with 3 water amounts (W1, W2 and W3) and 3 fertilizer amounts (F1, F2 and F3) were designed to form 9 combination treatments. The impacts of the irrigation and fertilization amounts on the fruit yield, qualities, nutrient uptakes, water and fertilizer use efficiencies, soil water contents and nutrient availabilities were analyzed in the study. The response relationships between the marketable yields , the root zone soil water and available nitrogen contents at different growth stages were built.【Result】 (1) Compared with W1, the total marketable yields were increased by 11.1%-12.8% under W2 and W3. The marketable yields were deceased by 10.4%-17.7% under W3 during the 1st-2nd fertigation managements, but which increased by 10.8%-26.2%, 21.2%-40.3% and 33.5%-46.4% under W2 and W3 during the 6th-8th, 10th-12th and 14th-16th fertigation managements, respectively. The rootzone (0-40 cm soil layer) soil water contents were increased by 4.2-6.4 percentage point by maintaining at the soil relative water content of 79%-87% uder W2 and W3 and the N, P2O5 and K2O uptakes by 17.9%-20.2%, 28.3%-36.3% and 25.9%-33.7%, respectively. However, the rootzone nitrate nitrogen contents were decreased by 9.1%-68.0% under W2 and W3, the water use efficiency by 31.1%-49.3%, and the fruit soluble solids, nitrate, soluble sugar and Vc contents by 7.4%-10.1%, 0.9%-5.4%, 5.9%-6.2% and 5.5%-12.8%, respectively. (2) Compared with F1, the total marketable yields were increased by 4.0%-7.9% under F2 and F3. The rootzone (0-40 cm soil layer) nitrate nitrogen contents were increased by 38.0%-162.0% under F2 and F3, and the N, P2O5 and K2O uptakes by 9.7%-13.1%, 7.9%-11.8% and 12.6%-17.3%, respectively. However, the fruit nitrate contents increased by 5.5%-14.6% under F2 and F3 and the partial factor productivities were deceased by 32.1%-47.8%. (3) From the view of whole growth period, W2F2 was recommended to drip irrigated cucumber because of the relatively higher yield, water and fertilizer use efficiencies and qualities, and lower residual soil nitrogen.【Conclusion】 For greenhouse cucumber with a target yield of 170-180 t·hm -2, the appropriate soil relative water contents were recommended as 63%, 78%, 82% and 85% during the March 21th- April 20th (the initial harvesting stage), April 21th-May 20th (the early vigorous harvesting stage), May 21th-June 20th (the vigorous harvesting stage) and June 21th-July 10th (the late harvesting stage), respectively. The corresponding low limits of soil relative water contents were recommended as 61%, 73%, 78% and 81%, respectively. The suitable rootzone nitrate nitrogen should be maintained at 25-40 mg·kg -1 during the yield formation.
