| In this paper,a typical farming area in “ rain fed regions ” of southern Henan was selected as the research area,and the soil type was sand ginger black soil.A field plot experiment was taken to test organic fertilizer substitution for chemical fertilizer in the maize ~ wheat rotation system.Normal fertilizer application(T0)and no nitrogen fertilizer application(N0)were set as control groups,and organic fertilizer substitution of 20%(T20),40%(T40),60%(T60),80%(T80),and 100%(T100)of chemical fertilizer were set as five experimental groups with a total of seven treatments.In the maize season,organic fertilizers were used to replace nitrogen fertilizers,and in the wheat season no replacement was made and chemical fertilizers were applied normally.A comprehensive discussion and analysis of crop growth,resistance to overwhelm and soil fertility indexes during the growth of maize and wheat was conducted to provide suitab.replacement ratios and alternatives for organic fertilizers to replace chemical fertilizers in the production of maize and wheat in “rain fed regions” of southern Henan.The main conclusions are as follows:(1)The application of organic fertilizer significantly increased the biomass and yield of maize,among which the biomass increased by 9.15% to 37.98%,5.47% to 20.49%,and 5.19% to17.39% at the jointing stage,silking stage and mature stage of maize,respectively,and the yield of maize increased by 9.6% to 21.87%.With the increase in the proportion of organic fertilizer replacing chemical fertilizer,the biomass and the yield of maize showed a trend of first increasing and then decreasing,and basically all of them were maximum at the substitution ratio of 60%,which was the best substitution ratio.Organic fertilizer substitution for chemical fertilizer mainly affected yield by affecting the ear diameter and 100 grain weight of maize,and yield was highly significantly and positively correlated with ear diameter and 100 grain weight.The application of organic fertilizer significantly increased the biomass and yield of wheat,and the biomass increased by 8.48% to 45.38%,15.44% to 37.78%,and 7.61% to 34.08% at the jointing stage,flowering stage and mature stage of wheat,respectively,and the yield increased by2.11% to 20.41%.With the increase in the proportion of organic fertilizer substitution for chemical fertilizer,the biomass and yield of wheat showed a trend of first increasing and then decreasing,basically the maximum substitution ratio was 60%,and the wheat yield increased significantly by45.38%,25.8% and 34.08% at the jointing stage,flowering stage and mature stage of wheat,and the wheat yield increased by 20.41%,which was the best substitution ratio.Organic fertilizer substitution for chemical fertilizer mainly affected the yield of wheat by affecting the number of spikes and thousand grain weight of wheat,and the yield was significantly and positively correlated with the number of spikes and thousand grain weight,and weakly correlated with the grain number per spike.(2)The application of organic fertilizer significantly increased the photosynthesis and functional leaf SPAD values of maize.The net photosynthetic rate,stomatal conductance and transpiration rate of maize treated with organic fertilizer increased by 5.63% to 40.87%,5.56% to27.78% and 9.22% to 47.09% at the jointing stage and 11.83% to 27.67%,9.09% to 40.91% and4.45% to 32.88% at the silking stage,respectively,and SPAD values increased by 13.22% to52.20% and 4.91% to 18.3% at the jointing and silking stages of maize,respectively.With the increase in the proportion of organic fertilizer replacing nitrogen fertilizer,photosynthetic parameters and SPAD values showed a trend of first increasing and then decreasing,where the parameter values were the largest and photosynthesis was the strongest at 60% replacement ratio,which was the best replacement ratio.The application of organic fertilizer significantly enhance the photosynthesis of wheat,and the net photosynthetic rate,stomatal conductance,and transpiration rate of wheat increased by1.15% to 13.53%,12.50% to 37.50%,and 0.93% to 6.94% at the jointing stage,and by 6.16% to26.30%,6.25 to 18.75%,and 1.90% to 13.92% at the flowering stage,respectively.The application of organic fertilizer increased the functional leaf SPAD values of wheat,which increased by 12.48% to 38.16% and 1.72% to 29.05% at the jointing and flowering stages,respectively.With the increase of the proportion of organic fertilizers replacing chemical fertilizers,the SPAD values of wheat showed a trend of increasing and then decreasing,with the maximum value at 60%,and the photosynthetic parameters showed a trend of increasing and then decreasing,with the maximum parameter value and the most intense photosynthesis at the substitution ratio of60%.(3)The application of organic fertilizers increased the nutrient content of maize plants in all growth periods,and with the increase of substitution ratio,the nitrogen,phosphorus and potassium content of maize plants tended to increase first and then decrease,with the maximum content of nitrogen,phosphorus and potassium at 60% substitution.The high substitution ratio was not conducive to the accumulation of nitrogen,phosphorus and potassium in maize;the increase in the accumulation of nitrogen was mainly the largest increase in the flowering stage and the highest value in the maturity stage,the increase in the accumulation of phosphorus was mainly in the maturity stage and the accumulation of potassium showed a steady increase with the growth of maize crop.The application of organic fertilizer increased the nutrient content of wheat plants in each growth period.With the increase of substitution ratio,the content of nitrogen,phosphorus and potassium of wheat plants tended to increase first and then decrease,with the maximum content of nitrogen,phosphorus and potassium at 60% of substitution.The high substitution ratio was not conducive to the accumulation of nitrogen,phosphorus and potassium of wheat plants;among them,the accumulation of nitrogen of wheat mainly acted at maturity,the accumulation of phosphorus mainly acted at maturity,and the accumulation of potassium steadily increased with the fertility cycle of wheat.(4)The application of organic fertilizer reduced the height of maize plant,ears position and center of gravity,with the lowest value at 60% substitution ratio.The application of organic fertilizer increased the stalk thickness of the 3rd node at the base of the maize plant,which tended to increase and then decrease with the increase of the substitution ratio,with the highest value at60% substitution ratio.The application of organic fertilizer reduced the length of the 3rd node stalk at the base of the maize plant,which tended to decrease and then increase with the increase of the substitution ratio,and the shortest stalk length was found at the substitution ratio of 60%.The application of organic fertilizer increased the force required to push down 45°,crushing strength,and puncture strength of maize plants,with the largest value at 60% substitution ratio.The application of organic fertilizer increased the index of resistance to overturning of maize,which tended to increase and then decrease with the increase of substitution ratio,and the index of resistance to overturning was the greatest at 60% of substitution ratio,and the resistance to overturning was the strongest.The application of organic fertilizer increased plant height,internode length under the ear,center of gravity,basal 2nd node length,basal 2nd node diameter,and fresh weight of single plant,with no obvious change pattern with the change of substitution ratio,and the maximum value was at 60% substitution ratio.The application of organic fertilizer increased the crushing strength,puncture strength and mechanical strength of wheat plants,and there was no significant change pattern with the substitution ratio,and the maximum value was at the substitution ratio of 60%;there was no significant change pattern in the wheat resistance index,and the maximum resistance index and the strongest resistance to fall was found when the substitution ratio was 60%.(5)The application of organic fertilizer reduced soil bulk density,increased soil p H and water content,significantly increased soil organic matter content,improved soil properties and increased soil fertility in the maize season.Compared with the treatment without chemical fertilizer,the application of organic fertilizer treatment reduced soil bulk weight by 7.43% to 22.2%,increased soil p H by 0.42% to 5.69%,increased soil water content by 0.81% to 21.1%,and significantly increased soil organic matter content by 12.3% to 46.6%.The application of organic fertilizer reduced wheat season soil bulk weight,increased soil p H,water content,significantly increased soil organic matter content,improved soil properties and increased soil fertility.Compared to the treatment without chemical fertilizer,the application of organic fertilizer treatment decreased soil bulk weight by 2.62% to 15.11%,increased soil p H by2.41% to 9.39%,increased soil water content by 0.86% to 11.52%,and significantly increased soil organic matter content by 4.13% to 139.17%.(6)Sucrase and urease of maize soil had the highest activity at the jointing stage,while phosphatase had the highest activity at the silking stage.The application of organic fertilizer significantly increased the contents of sucrase and neutral phosphatase in maize soil,and sucrase and neutral phosphatase increased by 5.1% to 30.7%,15.1% to 42.2%,1.4% to 42.8% and 5.8% to48.9%,14.1% to 39.6%,28.4% to 81.6% at the jointing,silking and maturity stages,respectively,all with the most significant increase at a substitution ratio of 60%.The application of organic fertilizer reduced soil urease content by 31.4% to 40.1%,4.9% to 25.7%,and 6.3% to 43.1% at jointing,silking,and maturity stages,respectively.The sucrase content of wheat soils increased continuously with the growth period,and reached the maximum at the mature stage,while the urease content decreased slowly,and the activity was the highest at the jointing stage.The neutral phosphatase increased and then decreased and the content was the highest in the flowering stage.The application of organic fertilizer significantly increased the content of sucrase,urease,and neutral phosphatase in wheat soil by 3.2% to 21.9%,7.7% to 33.7%,0.8% to 36.4%,1.9% to 55.9%,3.1% to 63.3%,0.8% to14.1%,and 31.6% to 73.1%,12.1% to 67.1%,17.9% to 82.5% at the jointing,flowering,and maturity stages,respectively,in which the content of the three enzymes tended to increase first and then decrease with the increase of substitution ratio,all of which were greatest at the substitution ratio of 60%.(7)The soil soluble organic carbon content of maize was the highest at the silking stage,which increased and then decreased with the fertility of maize,and the soil soluble organic nitrogen content increased slowly with the growth of maize.The application of organic fertilizer significantly increased soil soluble organic carbon and soluble organic nitrogen contents of maize,with significant increases of 7.5% to 50.9%,1.2% to 38.2%,7.1% to 44.2% and 8.6% to 64.3%,5.56% to 35.3%,1.41% to 42.9% at the jointing stage,silking stage and flowering stage,respectively,and when the replacement ratio was 60%,the soil soluble organic carbon and soluble organic nitrogen content were the highest.The soil soluble organic carbon content of wheat was the highest at the flowering stage and tended to increase and then decrease with wheat fertility,and the soil soluble organic nitrogen content increased with maize growth.The application of organic fertilizer significantly increased the soil soluble organic carbon and soluble organic nitrogen contents of wheat by 2.3% to 34.8%,21.1% to 70.9%,24.5% to 47.1% and 11.1% to 40.2%,13.2% to 42.8%,1.1% to 28.4% at the jointing stage,flowering stage and mature stage,respectively,and when the replacement ratio was60%,the soil soluble organic carbon and soluble organic nitrogen content were the highest. |
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