Effects of fertigation strategies on water and nitrogen distribution under water storage pit irrigation for orchards

Water storage pit(WSP)irrigation is a simple and inexpensive technology suitable for orchards in semiarid and arid regions of North China.This study compared the effects of different fertigation strategies on water and nitrogen distribution,and ammonia volatilization.A fertigation experiment was conducted using a 30°wedge-shaped plexiglass soil container,which represents one-twelfth of the complete storage pit.The height of the container was 120 cm,and a plexiglass damper for simulating the zero flux plane of adjacent water storage pits was located at the 40 cm radius.Four fertigation strategies were used for WSP irrigation:solution application during the first half(N-W),the last half(W-N),the middle half of an irrigation cycle(W-N-W),and during the entire irrigation(N-N).Surface(SF)irrigation was used as a control treatment with solution application during the entire irrigation(SN-N).The experimental results showed that the soil water and ammonium contents at 0-10 cm soil depth under WSP irrigation were only 10.51%and 18.42% of those under SF irrigation,respectively.The cumulative NH3 volatilization under WSP irrigation was 51.71%-68.72% lower compared with that under SF irrigation.The soil water distributions were similar for all four fertigation strategies.NH3 volatilization mainly occurred at the pit wall interface,and cumulative NH3 volatilization loss followed the trend N-N>W-N>W-N-W>N-W.Ammonium was adsorbed into the soil and thus mostly remained near the pit wall.Low concentrations of ammonium were found near the edge of the wetting zone under all strategies.Compared to N-W,N-N and W-N-W treatments,W-N treatment decreased the nitrate accumulation at 80-90 cm by 38.6%,19.0%and 10.3%,respectively.The W-N strategy was suggested for minimizing potential nitrate leaching.

Nitrogen distribution in the products from the hydrothermal liquefaction of Chlorella sp. and Spirulina sp.

The high contents of nitrogen-containing organic compounds in biocrude obtained from hydrothermal liquefaction of microalgae are one of the most concerned issues on the applications and environment.In the project,Chlorella sp.and Spirulina sp.were selected as raw materials to investigate the influence of different reaction conditions(i.e.,reaction temperature,residence time,solid loading rate)on the distribution of nitrogen in the oil phase and aqueous phase.Three main forms of nitrogen-containing organic compounds including nitrogen-heterocyclic compounds,amide,and amine were detected in biocrudes.The contents of nitrogen-heterocyclic compounds decreased with temperature while amide kept increasing.The effect of residence time on the components of nitrogen-containing organic compounds was similar with that of temperature.However,the influence of solid loading rate was insignificant.Moreover,it was also found that the differences of amino acids in the protein components in the two microalgae might affect the nitrogen distribution in products.For example,nitrogen in basic amino acids of Spirulina sp.preferred to go into the aqueous phase comparing with the nitrogen in neutral amino acids of Chlorella sp.In summary,a brief reaction map was proposed to describe the nitrogen pathway during microalgae hydrothermal liquefaction.

The Effects of Water and Fertilizer Coupling on Plant and Soil Nitrogen Characteristics and Fruit Growth of Rabbiteye Blueberry Plants in a Semi-Arid Region in China

To evaluate the effects of nitrogen(N)and irrigation coupling on the soil N distribution,plant N utilization,and fruit yield of rabbiteye blueberries(Vaccinium virgatum),a field experiment was designed using two factors(water and fertilizer application)with four levels of irrigation and three levels of fertilization,and a control.Under the different water and fertilizer combinations,N primarily accumulated in the leaves.Irrigation and N application within appropriate ranges(pure N≤29 g/plant and irrigation volume≤2.5 L/plant)significantly improved the blueberry fruit yield.Increases in water and N within these ranges promoted the effective accumulation of N in various organs and the absorption and utilization of N in the plants,which ultimately promoted blueberry yield.With increased N application rate,the nitrate N content of the 0–20 cm and 20–50 cm soil layers increased.With increased irrigation volume,the nitrate N content of the 0–20 cm soil layer decreased,while the nitrate content in the 20–50 cm soil layer increased.Low N and moderate water treatments resulted in high fruit yields and reduced nitrate N retention in the soil.Under these conditions,the economic input-output ratio was high and the soil N accumulation was low,and thus the economic and ecological benefits were maximized.

The Impacts of Supplemental Irrigation Based on Soil Moisture Measurement and Nitrogen Use on Winter Wheat Yield and Nitrogen Absorption and Distribution

Based on split plot design method of field test,the impacts of supplemental irrigation based on soil moisture measurement and nitrogen use on winter wheat yield and nitrogen absorption and distribution were studied.Supplemental irrigation had three levels: 60%(W_1),70%(W_2) and 80%(W3) of the targeted relative water content at 0-40 cm of soil layer during jointing period of winter wheat.Nitrogen fertilization had three levels: not using nitrogen(N_0),using pure nitrogen of 195 kg/hm^2(N_(195)) and 255 kg/hm^2(N_(255)).Results showed that:(i)different supplemental irrigation and nitrogen fertilization significantly affected plant height and leaf area of winter wheat during key growth period.Under the same supplemental irrigation treatment,both plant height and leaf area of winter wheat showed as N_(255)> N_(195)> N_0(P <0.05).Plant height in N_(195) and N_(255)treatments was significantly higher than that in N_0 treatment,but there was not significant difference between N_(195) and N_(255)(P >0.05).Under the same nitrogen fertilization,plant height in W_2(569.4 m^3/hm^2) and W3(873.45 m^3/hm^2) treatments was significant higher than that in W_1(265.2 m^3/hm^2),but there was not significant difference between W_2 and W3(P >0.05).It illustrated that excessive nitrogen fertilization and supplemental irrigation did not significantly affect plant height and leaf area of winter wheat.(ii) Under the same nitrogen fertilization level,yield increase effect of winter wheat by supplemental irrigation showed a declining trend with nitrogen application amount increased.It illustrated that nitrogen fertilization and supplemental irrigation had certain critical values on the yield of winter wheat.When surpassing the critical value,the yield declined.When nitrogen fertilization amount was 195 kg/hm^2,and supplemental irrigation amount was 70% of field moisture capacity(569.4 m^3/hm^2),the highest yield 8500 kg/hm^2 could be obtained.(iii) During mature period of winter wheat,nitrogen accumulation amount of plant treated by nitrogen was significantly higher than that not treated by nitrogen(P <0.05).But under the treatments of W_2 and W3,nitrogen accumulation amount in N_(255) significantly declined when compared with N_(195)(P <0.05).Especially under W3(873.45 m^3/hm^2) level,nitrogen accumulation amount in N_(255) was even lower than N_0.Under the treatments of N_0 and N_(195),nitrogen accumulation amount of plant significantly increased with supplemental irrigation increased(P < 0.05).But under N_(255) treatment,there was not significant difference(P > 0.05).It illustrated that moderate supplemental irrigation and nitrogen fertilization could improve nitrogen absorption ability of winter wheat,but excessive supplemental irrigation and nitrogen fertilization were not favorable for plant's nitrogen absorption.(iv) Although the increase of supplemental irrigation during jointing period improved nitrogen absorption ability of winter wheat and promoted winter wheat absorbing more nitrogen,it inhibited nitrogen transferring and distributing to seed.Comprehensively considering growth condition of winter wheat and nitrogen risk condition,it is suggested that nitrogen application amount was 195 kg/hm^2,and supplemental irrigation reached 70% of field moisture capacity(569.4 m^3/hm^2),which could be as the suitable water and fertilizer use amounts in the region.

Effects of the buried straw layer on soil water and nitrogen distribution under different irrigation limits

At present,water and fertilizer use efficiency is low in many cultivation areas in southern China.Studies show that the buried straw layer can effectively conserve water and fertilizer.To investigate the optimal irrigation upper limit above the straw barrier and its effect on soil moisture and nitrogen distribution,an indoor soil column experiment was conducted.Six treatments were designed consisting of two levels of straw layer i.e.,(with and without buried straw layer at 25 cm depth),and three irrigation water upper limits i.e.,(saturated moisture content(s),field water holding capacity(f),and 80%of field water holding capacity(0.8f)as the upper limit of irrigation).The result revealed that the buried straw layer can inhibit water infiltration and significantly increase the water storage capacity and water storage efficiency of 0-25 cm soil depth.Under the condition of no evaporation,when the upper limit of irrigation water does not exceed the field water holding capacity,the storage efficiency of 0-25 cm soil water reaches 89%-91%after 6 d.Moreover,a buried straw layer can inhibit the deep percolation of nitrate nitrogen and increase the amount of nitrate-nitrogen in 0-25 cm soil.The 80%field water holding capacity irrigation upper limit combined with straw interlayer treatment had a higher nitrate-nitrogen content in the 0-25 cm soil layer than other treatments.Therefore,80%of field water holding capacity as the upper limit of irrigation combined with buried straw layer is the optimal strategy to conserve soil water and nitrogen in the upper soil profile.

Effects of digestate application depth on soil nitrogen volatilization and vertical distribution

This study investigated the effect of the digestate application depth on soil nitrogen volatilization and vertical distribution in black loam soil and sandy loam column.The contents of soil moisture,TKN(total Kjeldahl nitrogen),ammonium nitrogen,nitrate nitrogen,and the extent of ammonia volatilization were tested by applying digestate at depths of 0 cm,2 cm,6 cm,10 cm,15 cm and 20 cm,respectively.The experimental results showed that ammonia volatilization mainly occurred in the first 10 days and reduced significantly when the application depth was deeper than 10 cm.At the same application depth,compared with the black loam,the nitrogen loss in sandy loam through ammonia volatilization was less,and the penetration depth of nitrate nitrogen and ammonium nitrogen were all deeper.In the same soil,nitrate nitrogen penetrated deeper than ammonium nitrogen at all application depths.

Effects of sowing methods on nitrogen compounds and protease activities of whole‐crop wheat silage

Background:Whole‐crop wheat(Triticum aestivum)has high nutritive value,and it has become one of the main sources of roughage for ruminants in some countries or regions.This study investigates the effects of no tillage on nitrogen compounds and protease activities of whole‐crop wheat silage.Methods:Wheat was planted on the 9th day(NB9)and 5th day(NB5)before rice harvest and on the first day after rice harvest.Sowing before harvest involved no tillage and sowing after rice harvest involved either no tillage(NA1)or conventional tillage(CK).Results:Compared to CK,the crude protein content of NB9 and NB5 decreased by 16.4%and 9.58%,respectively.With the delay of the sowing date,the contents of non‐protein nitrogen,rapidly degraded protein,and slowly degraded protein in whole‐plant wheat tended to increase.Compared to NA1 wheat silage,the NH_(3)‐N content of NB9 and NB5 silages decreased by 52.7%and 34.4%,respectively.The acid protease activity of NA1 was significantly higher than that of other treatments(p<0.05).Conclusions:There was no significant difference in the degree of protein degradation between NA1 and CK silages.Although the degree of protein degradation in early sowing was low,the degree of fermentation was also weak.