Study on Chromosome Doubling for Haploid Produced by Wheat×Maize Crossing

There is no spontaneous chromosome doubling in haploid plants produced by wheat X maize crossing. In order to obtain doubled haploid, two chromosome doubling methods were used. Results showed that: After adding colchicine solution directly into a medium for young embryos that had been cultured 7 days, frequencies of embryo germination in colchicine concentrations of 50mg/L, 100mg/L and 200mg/L were 32.1% , 26.4% and 16.3% , respectively, and frequencies of chromosome doubling were 85.3% , 100% and 50.0% , respectively. But in the control without colchicine, the frequency of embryo germination was 67.4% and no seed was setting. As the time of colchicine treatment increased from 24 to 72 hours, the frequency of embryo germination was reduced, and 24 hours had better results. After soaking seeding crowns and roots with colchicine solution of 500mg/L, 750mg/L and 1 000mg/L for 5 hours, the frequencies of doubling were 89.6%, 76.0% and 73.3%, respectively. By soaking crowns and roots of strong seedings with 500mg/L colchicine solution, the frequency and efficiency of doubling were 98.2% and 93.2% , respectively.

Identifying the critical phosphorus balance for optimizing phosphorus input and regulating soil phosphorus effectiveness in a typical winter wheat-summer maize rotation system in North China

Phosphorus(P)is a nonrenewable resource and a critical element for plant growth that plays an important role in improving crop yield.Excessive P fertilizer application is widespread in agricultural production,which not only wastes phosphate resources but also causes P accumulation and groundwater pollution.Here,we hypothesized that the apparent P balance of a crop system could be used as an indicator for identifying the critical P input in order to obtain a high yield with high phosphorus use efficiency(PUE).A 12-year field experiment with P fertilization rates of 0,45,90,135,180,and 225 kg P_(2)O_(5)ha^(-1)was conducted to determine the crop yield,PUE,and soil Olsen-P value response to P balance,and to optimize the P input.Annual yield stagnation occurred when the P fertilizer application exceeded a certain level,and high yield and PUE levels were achieved with annual P fertilizer application rates of 90-135 kg P_(2)O_(5)ha^(-1).A critical P balance range of 2.15-4.45 kg P ha^(-1)was recommended to achieve optimum yield with minimal environmental risk.The critical P input range estimated from the P balance was 95.7-101 kg P_(2)O_(5)ha^(-1),which improved relative yield(>90%)and PUE(90.0-94.9%).In addition,the P input-output balance helps in assessing future changes in Olsen-P values,which increased by 4.07 mg kg^(-1)of P for every 100 kg of P surplus.Overall,the P balance can be used as a critical indicator for P management in agriculture,providing a robust reference for limiting P excess and developing a more productive,efficient and environmentally friendly P fertilizer management strategy.

基于留一交叉验证法的APSIM-Maize产量模拟

作物生长模型APSIM广泛应用于作物估产和农业生产管理中,在观测数据有限的情况下,开展留一交叉验证是提高模型模拟能力的关键途径。本研究以内蒙古十大孔兑地区春玉米为研究对象,量化分析了APSIM-Maize模型模拟2012—2019年间玉米产量对关键参数的敏感性,并根据参数敏感性强弱对APSIM-Maize模型进行交叉验证与参数率定,提高了模型模拟能力。主要结果为:(1)影响春玉米产量的敏感性参数由强到弱依次是:蒸腾效率系数、辐射利用效率、开花到成熟的积温、出苗到拔节的积温、开花到灌浆的积温、潜在灌浆速率、光周期和最大穗粒数;(2)交叉验证时,APSIM-Maize模型各参数变异系数在1.06%~23.32%之间波动,总体上模型参数变异性小,可靠性高;(3)APSIM-Maize模型经过参数率定后的模拟产量与实测产量具有较好的一致性(R^(2)=0.72,RMSE=401.5kg hm^(-2)),模型在十大孔兑地区春玉米产量的评估中表现出较好的适应性。本研究为在农田试验数据有限情况下提高模型率定参数的可靠性提供了新的研究思路和科学依据。

Allelopathy of decomposed maize straw products on three soilborn diseases of wheat and the analysis by GC-MS

In northern China, the soil-born diseases of wheat have been getting more and more serious under a new farming system that returns maize straw to the field. In order to investigate the allelopathy of the decomposed maize straw products on three soil-born diseases of wheat, culture dish and pot experiments were conducted and the compounds in the products were identified by gas chromatography-mass spectrometry （GC-MS）. Culture dish experiments showed that the mycelial growth, sclerotia formation amount and total weight of Rhizoctonia cerealis were promoted at concentrations of 0.03, 0.06 and 0.12 g mL-1 and inhibited at concentration of 0.48 g mL-1 of the decomposed products. No significant effects were found of the product concentrations on average weight of the sclerotia. Mycelial growth of Gaeumannomyces graminis was promoted at almost all concentrations except the highest one. Mycelial growth and spore germination of Bipolaris sorokiniana were significantly inhibited by all concentrations of the decomposed products, with enhanced inhibition effects along with the increased concentrations. The length, number and dry weight of roots together with the root superoxide dismutase activity were promoted by the lowest concentration （0.03 g mL-1）, with a synthetic effect index of 0.012, and inhibited by other concentrations. The ion leakage of roots was increased and the root peroxidase activity of roots was lowered by all the treatments. Pot experiments revealed that occurrence of the sharp eyespot was reduced by 0.03 and 0.06 g mL-1 of decomposed products after irrigation. However, the incidence rates and disease indexes were significantly increased by 0.12, 0.24 and 0.48 g mL-1 of decomposed products. The results indicated that incidence rates and disease indexes of the take-all were significantly promoted after being irrigated with the decomposed products, while occurrences of the common rot didn＇t change, significantly. GC-MS results showed that the compounds of the decomposed products included organic acids, esters, hydrocarbons, amides and aldehydes, with the proportions 25.26, 24.01, 17.22, 14.39 and 7.73%, respectively. Further analysis investigated that the allelochemicals identified in straw decomposed products contained p-hydroxybenzoic acid （9.21%）, dibutyl phthalate （6.94%）, 3-phenyl-2-acrylic （5.06%）, 4-hydroxy-3,5-dimethoxybenzoic acid （2.26%）, hexanoic acid （1.73%）, 8-octadecenoic acid （1.06%）, 3-（4-hydroxy-3-methoxy-phenyl）-2-propenoic acid （1.04%）, 4-hydroxy-3-methoxy-benzoic acid （0.94%） and salicylic acid （0.94%）.

Trends of Yield and Soil Fertility in a Long-Term Wheat-Maize System

The sustainability of the wheat-maize rotation is important to China＇s food security. Intensive cropping without recycling crop residues or other organic inputs results in the loss of soil organic matter （SOM） and nutrients, and is assumed to be non- sustainable. We evaluated the effects of nine different treatments on yields, nitrogen use efficiency, P and K balances, and soil fertility in a wheat-maize rotation system （1991-2010） on silt clay loam in Shaanxi, China. The treatments involved the application of recommended dose of nitrogen （N）, nitrogen and phosphorus （NP）, nitrogen and potassium （NK）, phosphorus and potassium （PK）, combined NPK, wheat or maize straw （S） with NPK （SNPK）, or dairy manure （M） with NPK （M1NPK and M2NPK）, along with an un-treated control treatment （CK）. The mean yields of wheat and maize ranged from 992 and 2 235 kg ha-1 under CK to 5 962 and 6 894 kg ha-1 under M2NPK treatment, respectively. Treatments in which either N or P was omitted （N, NK and PK） gave significantly lower crop yields than those in which both were applied. The crop yields obtained under NP, NPK and SNPK treatments were statistically identical, as were those obtained under SNPK and MNPK. However, M2NPK gave a significant higher wheat yield than NP, and MNPK gave significant higher maize yield than both NP and NPK. Wheat yields increased significantly （by 86 to 155 kg ha-1 yr-1） in treatments where NP was applied, but maize yields did not. In general, the nitrogen use efficiency of wheat was the highest under the NP and NPK treatments; for maize, it was the highest under MNPK treatment. The P balance was highly positive under MNPK treatment, increasing by 136 to 213 kg ha-1 annually. While the K balance was negative in most treatments, ranging from 31 to 217 kg ha^-1 yr^-1, levels of soil available K remained unchanged or increased over the 20 yr. SOM levels increased significantly in all treatments. Overall, the results indicated that combinations of organic manure and inorganic nitrogen, or retuming straw with NP is likely to improve soil fertility, increasing the yields achievable with wheat-maize system in a way which is environmentally and agronomically beneficial on the tested soil.

Effects of saline irrigation on soil salt accumulation and grain yield in the winter wheat-summer maize double cropping system in the low plain of North China

In the dominant winter wheat （WW）-summer maize （SM） double cropping system in the low plain located in the North China, limited access to fresh water, especially during dry season, constitutes a major obstacle to realize high crop productivity. Using the vast water resources of the saline upper aquifer for irrigation during WW jointing stage, may help to bridge the peak of dry season and relieve the tight water situation in the region. A field experiment was conducted during 2009-2012 to investigate the effects of saline irrigation during WW jointing stage on soil salt accumulation and productivity of WW and SM. The experiment treatments comprised no irrigation （T1）, fresh water irrigation （T2）, slightly saline water irrigation （T3：2.8 dS m-l）, and strongly saline water irrigation （T4：8.2 dS m-1） at WW jointing stage. With regard to WW yields and aggregated annual WW-SM yields, clear benefits of saline water irrigation （T3 ＆ T4） compared to no irrigation （T1）, as well as insignificant yield losses compared to fresh water irrigation （T2） occurred in all three experiment years. However, the increased soil salinity in eady SM season in consequence of saline irrigation exerted a negative effect on SM photosynthesis and final yield in two of three experiment years. To avoid the negative aftereffects of saline irrigation, sufficient fresh water irrigation during SM sowing phase （i.e., increase from 60 to 90 mm） is recommended to guarantee good growth conditions during the sensitive early growing period of SM. The risk of long-term accumulation of salts as a result of saline irrigation during the peak of dry season is considered low, due to deep leaching of salts during regularly occurring wet years, as demonstrated in the 2012 experiment year. Thus, applying saline water irrigation at jointing stage of WW and fresh water at sowing of SM is most promising to realize high yield and fresh irrigation water saving.

Evaluation of Pathway of Nitrogen Loss in Winter Wheat and Summer Maize Rotation System

The nitrogen loss pathway in winter wheat and summer maize rotation system was studied based on field experimental data. The results showed that nitrogen recovery rate was significantly decreased with nitrogen fertilization rate increased, while residual rate and losses rate had an increasing trend. Accumulated ammonia volatilization loss in winter wheat and summer maize rotation was 12. 8(N0), 22.0(N120), 33. 0(N240) and 64. 5 kg N ha-1 (N360) respectively and rate of ammonia volatilization loss was 3.8, 4.2 and 7.2% respectively while urea was mixed with 0 -10 cm soil or spread before irrigation. Denitrification loss with acetylene-soil core incubation method in winter wheat was lower than 1 kg N ha-1 and rate of denitrification loss was 0. 21 - 0. 26% or trace. Denitrification loss in summer maize was 1 - 14 kg N ha-1 and rate of denitrification loss was 1-5%. The total gaseous loss in winter wheat and summer maize rotation system was less than 10%, and the main nitrogen fertilizer loss way was leaching below 0 - 100 cm soil profile and accumulated in deeper soil.

Study on Soil Denitrification in Wheat-Maize Rotation System

Soil denitrification was studied in wheat-maize rotation cropping system on an aquic cambisol. Results showed that the N loss amount by denitrification ranged from 4.7 to 9.7 kg per hectare with different levels of nitrogen application and the key stage for denitification was during summer maize-growth-period, especially within 1-2 weeks after fertilizer nitrogen was applied. Similar trend was found between soil N2O production/emission dynamic and denitrification dynamic in the rotation system, which may indicate that mainly N2O is produced in nitrification process.

Effects of long-term full straw return on yield and potassium response in wheat-maize rotation

The effect of long-term straw return on crop yield, soil potassium（K） content, soil organic matter, and crop response to K from both straw and chemical K fertilizer（K_2SO_4） were investigated in a fixed site field experiment for winter wheat-summer maize rotation in 6 years for 12 seasons. The field experiment was located in northern part of North China Plain with a sandy soil in relatively low yield potential. Two factors, straw return and chemical K fertilizer, were studied with two levels in each factor. Field split design was employed, with two straw treatments, full straw return of previous crop（St） and no straw return, in main plots, and two chemical K fertilizer treatments, 0 and 60 kg K2 O ha^（–1）, as sub-plots. The results showed that straw return significantly increased yields of winter wheat and summer maize by 16.5 and 13.2% in average, respectively, and the positive effect of straw return to crop yield showed more effective in lower yield season. Straw return significantly increased K absorption by the crops, with significant increase in straw part. In treatment with straw return, the K content in crop straw increased by 15.9 and 21.8% in wheat and maize, respectively, compared with no straw return treatment. But, straw return had little effect on K content in grain of the crops. Straw return had significant influences on total K uptake by wheat and maize plants, with an increase of 32.7 and 30.9%, respectively. There was a significant correlation between crop yield and K uptake by the plant. To produce 100 kg grain, the wheat and maize plants absorbed 3.26 and 2.24 kg K2 O, respectively. The contents of soil available K and soil organic matter were significantly affected by the straw return with an increase of 6.07 and 23.0%, respectively, compared to no straw return treatment. K_2SO_4 application in rate of 60 kg K2 O ha^（–1） showed no significant effect on wheat and maize yield, K content in crop straw, total K uptake by the crops, soil available K content, and soil organic matter. The apparent K utilization rate（percentage of applied K absorbed by the crop in the season） showed difference for wheat and maize with different K sources. In wheat season, the K utilization rate from K_2SO_4 was higher than that from straw, while in maize season, the K utilization rate from straw was higher than that from chemical fertilizer. In the whole wheat-maize rotation system, the K absorption efficiency by the two crops from straw was higher than that from K_2SO_4.

Influence of P-enriched compost application on economics and P use efficiency of a maize–wheat rotation system

Crop phosphorus(P) deficiency and poor utilization of added P is a major agricultural problem due to reduced solubility of soil P and rapid fixation or precipitation of applied P fertilizer in alkaline and calcareous soils. The effects of P-enriched compost and single superphosphate(SSP) fertilization on maize and wheat yields and P use efficiency in a maize–wheat rotation system were studied for three years. On a three-year average, grain yields of maize and wheat after application of P-enriched compost were increased by 18% and 24%, respectively, in comparison with sole addition of a recommended dose of SSP fertilizer. P-enriched compost addition to soil increased maize and wheat yields by 12% and 17%, respectively, compared to P fertilizer plus FYM incorporation. Soil available P concentration and P uptake were affected significantly by the addition of P-enriched compost. On average, increases in P recovery, use efficiency, and agronomic efficiency of 52%, 18%, and 43% were recorded in maize and increases of 50%, 23%, and 49% in wheat. P-enriched compost application yielded 30% and 32%higher economic returns in maize and wheat than SSP fertilization alone.

Effect of steam-flaking on chemical compositions,starch gelatinization,in vitro fermentability,and energetic values of maize,wheat and rice

Intact and steam-flaked grains of maize,wheat and rice（with whole hulls） were analyzed for chemical composition,starch gelatinization degree（SGD） and in vitro fermentation characteristics to investigate the influence of cereal type and steam-flaking（SF） processing on their nutritive values.The treatments were arranged in a 3×2 factorial design.Obvious differences（P〈0.001） in chemical composition and energetic values were observed among the different cereal types.SGD and gas production（GP） rate was significantly increased（P〈0.001） by SF processing.SF processing also increased（P〈0.01） the proportion of propionic acid and decreased the acetic：propionic acid ratio in vitro.Steam-flaking also increased organic matter digestibility and the energetic value of the cereal grains,especially rice.Based on these results,rice probably is more amendable to SF processing than maize and wheat.In conclusion,it is feasible to partially substitute maize grain with wheat or rice in ruminant diets,and steam-flaking can significantly improve the nutritional value of wheat and rice grains.

Effects of mulches on water use in a winter wheat/summer maize rotation system in Loess Plateau, China

Limited water resources often result in reduced crop yield and low water productivity（WP）. In northwestern China, crop production is generally dependent on precipitation. Therefore, a variety of agricultural rainwater harvesting（ARH） techniques have been used for conserving soil moisture, ameliorating soil environment, increasing crop yield, and improving water use efficiency. A two-year（2013–2015） field experiment was conducted under a typical sub-humid drought-prone climate in Yangling（108°24′E, 34°20′N; 521 m a.s.l.）, Shaanxi Province, China, to explore the effects of mulching（same for summer maize and winter wheat） on soil moisture, soil temperature, crop water consumption, and crop yield with a winter wheat/summer maize rotation. Crops were planted in a ridge-furrow pattern and the treatments consisted of a transparent film mulch over the ridges（M1）, a crop straw mulch in the furrows（M2）, a transparent film mulch over the ridges and a crop straw mulch in the furrows（M3）, a black film mulch over the ridges and a crop straw mulch in the furrows（M4）, and a control with no mulch（CK）. Results showed that M4 was the best treatment for improving soil water storage and content, and decreasing crop water consumption during the summer maize and winter wheat rotation. In both maize and wheat seasons, M1 had a higher soil temperature than M2 and CK, and M3 had a higher soil temperature than M4. In the maize seasons, M4 had the highest yield, WP, and precipitation productivity（PP）, with the average values for these parameters increasing by 30.9%, 39.0%, and 31.0%, respectively, compared to those in CK. In the wheat seasons, however, M3 had the highest yield, WP, and PP, with the average values for these parameters being 23.7%, 26.7%, and 23.8% higher, respectively, than those in CK. Annual yield（maize and wheat yields combined） and WP did not differ significantly between M3 and M4. These results suggested that M3 and M4 may thus be the optimal ARH practices for the production of winter wheat and summer maize, respectively, in arid and semi-arid areas.

Effects of three types of soil amendments on yield and soil nitrogen balance of maize–wheat rotation system in the Hetao Irrigation Area, China

Excessive fertilization combined with unreasonable irrigation in farmland of the Hetao Irrigation Area(HIR), China, has resulted in a large amount of nitrogen(N) losses and agricultural non-point source pollution.Application of soil amendments has become one of the important strategies for reducing N losses of farmland.However, there is still no systematic study on the effects of various soil amendments on N losses in the HIR.In this study, three types of soil amendments(biochar, bentonite and polyacrylamide) were applied in a maize–wheat rotation system in the HIR during 2015–2017.Yields of maize and wheat, soil NH3 volatilization, N2O emission and NO3– leaching were determined and soil N balance was estimated.The results showed that applications of biochar, bentonite and polyacrylamide significantly increased yields of maize by 9.2%, 14.3% and 13.3%, respectively, and wheat by 9.2%, 16.6% and 12.3%, respectively, compared with the control(fertilization alone).Applications of biochar, bentonite and polyacrylamide significantly reduced soil N leaching by 23.1%, 35.5% and 27.1%, soil NH3-N volatilization by 34.8%, 52.7% and 37.8%, and soil N surplus by 23.9%, 37.4% and 30.6%, respectively.Applications of bentonite and polyacrylamide significantly reduced N2O-N emissions from soil by 37.3% and 35.8%, respectively, compared with the control.Compared with application of biochar, applications of bentonite and polyacrylamide increased yields of maize and wheat by 5.1% and 3.5%, respectively.Our results suggest that soil amendments(bentonite and polyacrylamide) can play important roles in reducing N losses and increasing yield for the maize–wheat rotation system in the HIR, China.

Water consumption in summer maize and winter wheat cropping system based on SEBAL model in Huang-Huai-Hai Plain, China

Crop consumptive water use is recognized as a key element to understand regional water management performance. This study documents an attempt to apply a regional evapotranspiration model（SEBAL） and crop information for assessment of regional crop（summer maize and winter wheat） actual evapotranspiration（ET a） in Huang-Huai-Hai（3H） Plain, China. The average seasonal ET a of summer maize and winter wheat were 354.8 and 521.5 mm respectively in 3H Plain. A high-ET a belt of summer maize occurs in piedmont plain, while a low ET a area was found in the hill-irrigable land and dry land area. For winter wheat, a high-ET a area was located in the middle part of 3H Plain, including low plain-hydropenia irrigable land and dry land, hill-irrigable land and dry land, and basin-irrigable land and dry land. Spatial analysis demonstrated a linear relationship between crop ET a, normalized difference vegetation index（NDVI）, and the land surface temperature（LST）. A stronger relationship between ET a and NDVI was found in the metaphase and last phase than other crop growing phase, as indicated by higher correlation coefficient values. Additionally, higher correlation coefficients were detected between ET a and LST than that between ET a and NDVI, and this significant relationship ran through the entire crop growing season. ET a in the summer maize growing season showed a significant relationship with longitude, while ET a in the winter wheat growing season showed a significant relationship with latitude. The results of this study will serve as baseline information for water resources management of 3H Plain.

Response of dryland crops to climate change and drought-resistant and water-suitable planting technology:A case of spring maize

Climate change has a significant impact on agriculture.However,the impact investigation is currently limited to the analysis of meteorological data,and there is a dearth of long-term monitoring of crop phenology and soil moisture associated with climate change.In this study,temperature and precipitation(1957-2020)were recorded,crop growth(1981-2019)data were collected,and field experiments were conducted at central and eastern Gansu and southern Ningxia,China.The mean temperature increased by 0.36°C,and precipitation decreased by 11.17 mm per decade.The average evapotranspiration(ET)of winter wheat in 39 years from 1981 to 2019 was 362.1 mm,demonstrating a 22.1-mm decrease every 10 years.However,the ET of spring maize was 405.5 mm over 35 years(1985-2019),which did not show a downward trend.Every 10 years,growth periods were shortened by 5.19 and 6.47 d,sowing dates were delayed by 3.56 and 1.68 d,and maturity dates advanced by 1.76 and 5.51 d,respectively,for wheat and maize.A film fully-mulched ridge-furrow(FMRF)system with a rain-harvesting efficiency of 65.7‒92.7%promotes deep rainwater infiltration into the soil.This leads to double the soil moisture in-furrow,increasing the water satisfaction rate by 110‒160%.A 15-year grain yield of maize increased by 19.87%with the FMRF compared with that of half-mulched flat planting.Grain yield and water use efficiency of maize increased by 20.6 and 17.4%when the density grew from 4.5×10^(4)to 6.75×10^(4)plants ha-1 and improved by 12.0 and 12.7%when the density increased from 6.75×10^(4)to 9.0×10^(4)plants ha-1,respectively.Moreover,responses of maize yield to density and the corresponding density of the maximum yield varied highly in different rainfall areas.The density parameter suitable for water planting was 174 maize plants ha-1 with 10 mm rainfall.Therefore,management strategies should focus on adjusting crop planting structure,FMRF water harvesting system,and water-suitable planting to mitigate the adverse effects of climate change and enhance sustainable production of maize in the drylands.

The Effects of Three Mineral Nitrogen Sources and Zinc on Maize and Wheat Straw Decomposition and Soil Organic Carbon

The incorporation of straw in cultivated ifelds can potentially improve soil quality and crop yield. However, the presence of recalcitrant carbon compounds in straw slow its decomposition rate. The objective of this study was to determine the effects of different nitrogen sources, with and without the application of zinc, on straw decomposition and soil quality. Soils were treated with three different nitrogen sources, with and without zinc： urea （CO（NH2）2）, ammonium sulfate （（NH4）2SO4）, and ammonium chloride （NH4Cl）. The combined treatments were as follows：maize （M） and wheat （W） straw incorporated into urea-, ammonium sulfate-, or ammonium chloride-treated soil （U, S, and C, respectively） with and without zinc （Z） （MU, MUZ, WU, WUZ;MS, MSZ, WS, WSZ;MC, MCZ, WC, WCZ, respectively）;straw with zinc only （MZ, WZ）;straw with untreated soil （MS, WS）;and soil-only or control conditions （NT）. The experiment consisted of 17 treatments with four replications. Each pot contained 150 g soil and 1.125 g straw, had a moisture content of 80%of the ifeld capacity, and was incubated for 53 days at 25°C. The rates of CO2-C emission, cumulative CO2-C evolution, total CO2 production in the soils of different treatments were measured to infer decomposition rates. The total organic carbon （TOC）, labile organic carbon （LOC）, and soil microbial biomass in the soils of different treatments were measured to infer soil quality. All results were signiifcantly different （P〈0.05） with the exception of the labile organic carbon （LOC）. The maize and wheat straw showed different patterns in CO2 evolution rates. For both straw types, Zn had a synergic effect with U, but an antagonistic effect with the other N sources as determined by the total CO2 produced. The MUZ treatment showed the highest decomposition rate and cumulative CO2 concentration （1 120.29 mg/pot）, whereas the WACZ treatment had the lowest cumulative CO2 concentration （1 040.57 mg/pot）. The addition of NH4Cl resulted in the highest total organic carbon （TOC） concentration （11.59 mg kg-1）. The incorporation of wheat straw resulted in higher microbial biomass accumulation in soils relative to that of the maize straw application. The results demonstrate that mineral N sources can affect the ability of microorganisms to decompose straw, as well as the soil carbon concentrations.

The Effect of Organo-Mineral Fertilizer Applications on the Yield of Winter Wheat, Spring Barley, Forage Maize and Grass Cut for Silage

Biosolids were applied with urea to produce a granulated organo-mineral fertiliser (OMF) for application by farm fertiliser equipment to a range of agricultural crops. The recommended rates of nitrogen, phosphate and potash were calculated for the test crops using “The Fertiliser Manual”, which assesses the nutrient requirement based on previous cropping, rainfall and soil index. The OMF produced similar crop yields compared to ammonium nitrate fertiliser when applied as a top-dressing to winter wheat, forage maize and grass cut for silage in the cropping years 2010 to 2014. In 2012 the grain yield of spring barley top-dressed with OMF was significantly lower than the conventional fertiliser treatment, due to dry conditions following application. For this reason it is recommended that OMF is incorporated into the seedbed for spring sown crops and The Safe Sludge Matrix guidelines followed. The experimental work presented shows that OMF can be used in sustainable crop production systems as a source of nitrogen and phosphorus for a range of agricultural crops.

Effect of Different Fertilization Practices on Yield of a Wheat-Maize Rotation and Soil Fertility

A 15-year field experiment was carried out in Henan Province, China, to study the effects of different fertilization practices on yield of a wheat-maize rotation. Fertilizers tested contained N alone (N), N plus P (NP) or plus P and K (NPK), all with or without manure (M). Different long-term fertilization practices affected the yields under the rotation system of wheat and maize differently and the effects on yields was in a general trend of MNPK＞MNP＞MN＞NPK＞NP＞M＞N＞the control. The average contribution rate of soil fertility to the highest yield was 37.9%, and the rest 62.1% came from fertilizer applications. The yield effects of the chemical fertilizers were in the order of N＞P＞K and were increased by application of manure.Balanced fertilization with multielement chemical fertilizers and manure can be effective in maintaining growth in agricultural production. Combined application of chemical fertilizer and organic manure also increased the content of soil organic matter.

Effect of Nitrogen Management on Yield and Water Use Efficiency of Rainfed Wheat and Maize in Northwest China

A field experiment with four treatments and four replicates in a randomized complete block design was conducted at the Changwu Experimental Station in Changwu County, Shaanxi Province, of Northwest China from 1998 to 2002. The local cropping sequence of wheat, wheat-beans, maize, and wheat over the 4-year period was adopted. A micro-plot study using 15N-labelled fertilizer was carried out to determine the fate of applied N fertilizer in the first year. When N fertilizer was applied wheat (years 1, 2 and 4) and maize (year 3) grain yield increased significantly (P<0.05) (>30%), with no significant yield differences in normal rainfall years (Years 1, 2 and 3) for N application at the commonly application rate and at 2/3 of this rate. Grain yield of wheat varied greatly between years, mainly due to variation in annual rainfall. Results of 15N studies on wheat showed that plants recovered 36.6%-38.4% of the N applied, the N remained in soil (0-40 cm) ranged from 29.2% to 33.6%, and unaccounted-for N was 29.5%-34.2%. The following crop (wheat) recovered 2.1%-2.8% of the residual N from N applied to the previous wheat crop with recovery generally decreasing in the subsequent three crops (beans, maize and wheat).

A Novel Approach to the Water Uptake Dynamics in Roots of Maize,Wheat and Barley Under Salt Stress

The water uptake dynamics in maize,wheat,and barley under salt stress were investigated with a xylem pressure probe.The average xylem pressure responses to salt stress in the three plants were 36,93,and 89% of the osmotic stresses for maize,wheat,and barley,respectively,which are significantly smaller than the magnitude of the osmotic stresses being applied.In order to explain the thermodynamic discrepancies among the water potential changes in the root xylem of the three plants,a novel approach,tentatively named the ＂symplastic flow dilution model＂ was proposed in this paper.The model was presented in an attempt to give answers to the problem of how the roots under salt stress could absorb water when the water potential of the xylem sap is considerably higher than that of the solution in the root ambient.According to the model,the salt solution in the microenvironment of the endodermis of a root was diluted to some extent by the efflux from cells so the central stele of the root is not exposed to the same solution bathing the root with the same salt concentration.In contrast,we also presented another approach,the ＂reflection coefficient progression approach＂,which was less likely to be true because it requires a considerable amount of solute to be transported into the root xylem when the salt stress is severe.