Study on Physiological Characteristics and Supporting Techniques of Huayu 22 Peanut

Yaping ZHENG，Yongmei ZHENG，Zhengfeng WU，Xuewu SUN，Caibin WANG

Shandong Peanut Research Institute，Qingdao 266100，China

1 Introduction

Huayu 22 Peanut，bred by Shandong Peanut Research Institute，belongs to ordinary large variety of peanut with high quality，high yield potential and high stress resistance and it possesses typical characteristics of traditional export-oriented quality peanut［1］.Its pod yield is up to 11289 kg／hm2，making a new record of peanut yield［2］.Also，it has high drought resistance［3－4］and strong shade tolerance［5－8］.In different ecological areas，both the yield and quality are stable［9－10］.Since the Eleventh Five-Year Plan，Huayu 22 Peanut has been determined by Shandong Province as major variety for popularization.In recent years，the annual sown area of Huayu 22 Peanut keeps higher than 20 hm2.Thus，Huayu 22 Peanut plays an essential role in constant increase of peanut yield in Shandong and Huang-Huai-Hai Plain in North China.Ordinary large peanut is major peanut variety of Shandong Province.Study on nutrition characteristics，stress physiology and supporting techniques of Huayu 22 Peanut is conducive to further developing its application value in breeding and exploiting its high yield potential，and promoting scientific research and production of peanuts.There fore，we made a systematic study on some physiological characteristics and key supporting techniques of Huayu 22 Peanut since the 12th Five-Year Plan period.We discussed characteristics of shade tolerance，N nutrition characteristics and high yield cultivation techniques of Huayu 22 Peanut，in order to provide theoretical basis and technical support for giving full play to high yield potential of Huayu 22 Peanut and the same variety peanut.

2 Physiological basis of shade tolerance

2.1 Shading having little influence on photosynthesisCompared with the natural light intensity，the leaf area of peanut in shading condition decreases，and the photosynthesis rate declines.Moderate shading（50%shade）：there is no significant difference between leaf area and net photosynthesis rate of Huayu 22 and Baisha 1016 peanuts；heavy shading（85%shade）：decline rate of leaf area and net photosynthesis rate of Huayu 22 Peanut is 6.9%and 12.5%lower than Baisha 1016 Peanut.

2.2 Higher adaptive capacity to weak light stressIn natural light intensity，the light compensation point of Huayu 22 Peanut is 37.7%lower than Baisha 1016 Peanut，the apparent quantum yield（AQY）of Huayu 22 Peanut is 59.1%higher than Baisha 1016，showing higher ability of capturing light.Inmoderate shading condition，growth rate of chlorophyll（a＋b）content in Huayu 22 Peanut is16.6%higher than Baisha 1016 Peanut；chloroplast membrane is intact and chloroplast volume expands；within the chloroplast，there are more grana and granum lamella，and light energy moves faster in thylakoid.In heavy shading condition，the decline rate of chlorophyll（a＋b）content of Huayu 22 Peanut is 11.7%higher than Baisha 1016，there are more granum lamella，while chloroplast membrane of Baisha 1016 Peanut is not fully developed and granum lamella is damaged and the number significantly declined.

2.3 Quick recovery after removal of shade and high grow th compensation effect In moderate shading condition，leaf area of Huayu 22 Peanut after removal of shade takes15 days shorter than Baisha 1016 Peanut to recover to control level；in heavy shading condition，the leaf area of Huayu 22 Peanut takes20 days shorter than Baisha1016 Peanut.For two methods of shade treatment，dry matter accumulation rate of Huayu 22 Peanut takes 3－4 days shorter to the control level than Baisha 1016 Peanut.

2.4 Smaller decline of pod yieldCompared with natural light intensity，pod yield of penut in shade condition declines.In moderate shade condition，there is little difference in decline degree of pod yield between Huayu 22 Peanut and Baisha 1016 Peanut，the decline degree of pod yield of Huayu 22 Peanut was12.0%lower than Baisha 1016 Peanut in 2007；in heavy shade condition，the decline rate of pod yield of Huayu 22 Peanut was9.0%and 5.1%lower than Baisha 1016 Peanut in 2006 and 2007 respectively.

3 Characteristics of N nutrition

3.1 Intensity and proportion of N supply of three N sources at different growth stagesAt different growth stages，there are significant differences in intensity of N supply between three N sources.N supply intensity of root nodule takes on unimodal curve with peak bias：the pod setting stage＞pegging stage＞pod filling stage＞seedling stage；N supply intensity of soil takes on N shape with peak value at pegging stage followed by pod filling stage，pod setting stage and seedling stage；“N”supply intensity of N fertilizer takes on unimodal curve with peak value at pegging stage，namely，pegging stage＞pod setting stage＞seedling stage＞pod filling stage.The average N supply intensity of root nodule，soil and N fertilizer at the whole growth stage is 66.7 mg·m－2·d－1，42.3 mg·m－2·d－1，and 30.3 mg·m－2·d－1.

3.2 Supp ly volume of three N sources at different grow th stagesAt different growth stages，there are significant differences in N supply volume between three N sources.According to performance of N supply volume of root nodule，the pod setting stage＞pegging stage＞pod filling stage＞seedling stage.The accumulation volume of N at seedling stage，pegging stage，pod setting stage and pod filling stage accounts for 6.1%，25.4%，57.7%and 10.8%of total N supply volume of root nodule at the whole growth stage respectively；except seedling stage，N supply volume of soil is similar at other three stages，the accumulation volume of N at four stages accounts for 11.6%，30.4%，30.4%and 27.6%of total N supply volume of soil at the whole growth stage；N supply volume of N fertilizer is pod setting stage＞pegging stage＞seedling stage＞pod filling stage，and the accumulation volume of N accounts for 12.9%，29.8%，51.2%and 6.1%of total N supply volume at the whole growth stage respectively.

3.3 Proportion of supp ly volume of three N sources at different grow th stagesAt seedling stage，N of peanut mainly comes from soil，the contribution rate is up to 38.1%；at pegging stage，root nodule contributes the largest value to fixing nitrogen，up to 43.6%；at pod setting stage，root nodule contributes about 50%to N supply volume，while the proportion of soil and N fertilizer declines，accounting for about20%of total N supply volume；at pod filling stage，soil contributes the largest to N supply，the proportion is up to 56.3%，while root nodule drops to 34.6%，and N fertilizer has the smallest contribution with proportion only 9.1%.At the whole growth stage，root nodule is major N source，accounting for 50.0%of total N supply volume，followed by soil and N fertilizer，the proportion of root nodule，soil and N fertilizer is5：3：2.Thus，root nodule plays an essential role in metabolic process of peanut N and fully exploring N fixing potential of root nodule is an effective approach for increasing efficiency and reducing N fertilizer application.

3.4 N fertilizer utilization rate at different grow th stages

As for N fertilizer utilization rate，the pod setting stage＞pegging stage＞pod filling stage.N fertilizer utilization rate is 5.4%，12.6%，21.6%and 2.7%at four growth stages respectively.

4 Characteristics of supporting techniques

We established standardized supporting technique for simple cultivation of Huayu 22 Peanut with＂single-seed planting，high effective fertilizer application，and three sprays and multi-prevention＂.This supporting technique shows significant effect in increasing yield，saving costs and increasing efficiency after application in Shandong and Huang-Huai-HaiPlain in North China.Major points of this supporting technique are as follows：

4.1 Returning straws to field（organic fertilizer） ＋deep tillage，to realize combination of land use and nursingExcellent soil condition is foundation for high yield and constant yield increase of peanut.Soil management should focus on current stubble and consider long term，and should cultivate fertility on the basis of satisfying soil requirement of peanut.For land parcels implementing three crops in two years，it is recommended to return corn straws to field，and till the land for30 cm deep.If the previous crop is other crops，it is feasible to apply thoroughly decomposed poultry（or livestock）manure7.5－9.0 t／hm2，to increase soil organic content.

4.2 Reducing N and P fertilizer and increasing Ca and trace element fertilizerWith many years of experiment and production practice，we found that production of 1000 kg peanut pod needs organic fertilizer600－750 kg／hm2，20 kg N fertilizer，5－10 kg P2O5，and 20－25 kg K2O.Compared with ordinary fertilizer application，such application uses less N and P fertilizer for 20－40%and 25－50%respectively.According to N nutrition characteristics，with advance of growth stage of Huayu 22 Peanut，the proportion of N supply declines，the seedling stage accounts for 30%，the middle stage accounts for 20%，and the harvest stage drops to10%approximately.According to this result，to realize consistency of supply and demand of N fertilizer，the suitable proportion is as follows：ordinary N fertilizer accounts for 50%，fertilizer with release time of70－80 days accounts for 33－40%，and fertilizer with release time of100－120 days accounts for10－20%.

Besides，according to conditions of local soil nutrients，it is recommended to apply Ca fertilizer and trace element fertilizer every two years.Acid soil should use calcium containing alkaline fertilizer like lime，while alkaline soil should use calcium containing acid fertilizer like gypsum.

For pure peanut area（including spring sowing and summer direct sowing），spread organic fertilizer，N，P and K fertilizer and trace element fertilizer before rotary tillage，evenly rotary applying fertilizers into 0－20 cm topsoil；apply Ca fertilizer on soil surface before sowing，and apply fertilizers into 0－10 cm peanut setting layer at the time of ridging for sowing for the convenience of pod absorbing.For inter planting area，apply fertilizers except Ca fertilizer after wheat harvesting and before flowering，combining stubble-cleaning，and apply fertilizers into 5－10 cm soil beside peanut seedlings，cover soil and water after application，and apply Ca fertilizer and trace element fertilizers into5－10 cm peanut setting layer beside peanut plants before cultivation and earthing up.

4.3 Implementing single-seed fine planting in accordance w ith local situationsFor land parcels with annual yield above 4500 kg／hm2，conventional two seed bunch planting can be changed to single seed fine planting，which can save seed for about1／4.For pure cropping parcels，ridge space should be80－85 cm，ridge width should be50－55 cm，and ridge height should be 4－5 cm.On the ridge，sow 2 rows of peanuts at row spacing of30－35 cm；for spring sowing，the space between holes should be 11－12 cm，and sow 203000－218000 holes for one hectare；for summer direct sowing，the space between holes should be10－11 cm，and sow 203000－225000 holes for one hectare.For peanut inter cropping with wheat，it is recommended to adopt local planting method：row spacing 30－33 cm，space between holes13－15 cm，and sowing 218000－233000 holes for one hectare.For areas not suitable for single seed fine planting，it is recommended to adopt two seed bunch planting with density similar to general large peanut varieties.

4.4 Fine seeding to realize full seedlings in one time seeding

Before seeding，mix seeds（225－255 kg）with 30%Chlorpyrifos 3750 ml＋2.5%imidacloprid 750 ml＋Celest 300 ml for one hectare，to prevent root rot，aphids，and underground pests.For spring seeding，the suitable period is April25 to May 10.For inter cropping with wheat，sow peanuts 15－20 days before wheat harvesting.For summer seeding，it is required to complete sowing 3－4 days before harvest of previous crops.At the time of sowing，the relative moisture content of soil should be 70－75%.

Before spring sowing of peanuts，use rotary tiller to plow field one to two times，and adopt peanut combined seeding machine with excellent agronomic performance，and complete sowing，soil covering，suppression，spraying herbicide，film coverage，and soil pressing in one time.For inter cropping with wheat，use self-contained peanut inter planting machine or manual seeding.For summer direct seeding，after harvest of previous crops，sow peanuts in accordance with sequence of stubble cleaning，fertilizer application，tillage，rotary tillage，and mechanized sowing.For land parcels covered with plastic film，the soil coverage thickness above sowing row should be 3－4 cm，to ensure peanuts are able to break film and sprout.

4.5 Taking pertinent management measures in accordance with grow th condition of field plants

4.5.1 Early stage management.

（i）Promptly release seedlings，reseed，and dig out lateral braches of peanuts buried under film.

（ii）Water one to three times before wheat harvest for peanut inter cropping with wheat，to ensure smooth seedling emergency.

（iii）After wheat harvest，promptly cultivate，clean stubble，to pdress，and water，spray herbicide like acetochlor to prevent weeding.

Table 1 Implementation of three times of sprays and multi-prevention

4.5.2 Middle stage management.

（i）Implementing＂three sprays and multi-prevention＂to simplify field management.At different growth stages，properly combine bactericide，insecticide，and plant growth inhibitor according to growth condition of field plants，spray three times of pesticide at the whole growth stage，to effectively prevent pests and plant diseases，and solve lodging and early aging problems.

（ii）Water and earth up in proper time：when plant leaves show withering sign atnoon，it is required to promptly water.For open field cultivation，when field plants growth close to ridge closing，use plow to earth up between two rows of peanuts，to make more pegs insert into soils for pod setting.

4.5.3 Later stage management.

（i）Slightly water in case of drought，and promptly drain water in the event of flooding.

（ii）For spring sowing land parcels，when there are only 3－4 green leaves left in major stem of plant，and more than 70%pods be come mature，it is required to harvest peanuts in time.For peanuts inter cropping with wheat and direct summer sowing peanuts，the harvest time can be extended to the beginning of October，but it should not delay sowing of the following crops.

［1］WAN SB.Peanut production in China［M］.Shanghai：Shanghai Science and Technique Publishing House，2003.（in Chinese）.

［2］ZHANG JL，GUO F，LIXG，et al.New breakthrough of Chinese peanut cultivation techniques1 1250kg／ha under single－seed sowing pattern［J］.Journal of Peanut Science，2014，43（4）：46－49.（in Chinese）.

［3］ZHANGZM，WAN SB，DAILX，et al.Response of different peanut varieties to drought stress［J］.Chinese Journal of Eco－Agriculture，2011，19（3）：631－638.（in Chinese）.

［4］ZHANG ZM，DAI LX，DING H，et al.Identification and evaluation of drought resistance in different peanut varieties widely grown in Northern China［J］.Acta Agronomica Sinica，2012，38（3）：495－504.（in Chinese）.

［5］WU ZF，WANGCB，ZHENGYP，etal.Effects of shading at seedling stage on photosynthetic characteristics of Arachis hypogaea L.leaves［J］.Acta Ecologica Sinica，2009，29（3）：1366－1373.（in Chinese）.

［6］WU ZF，WANG CB，WAN GB，et al.Effects of weak light stress on development and pod yield of peanut（Arachis hypogaea L.）during seedling stage［J］.Journal of Peanut Science，2008，37（4）：27－31.（in Chinese）.

［7］WU ZF，LIU JH，WAN SB，et al.Effect of shading duration on pod yield and quality of peanut［J］.Shandong Agricultural Sciences，2011（2）：30－33.（in Chinese）.

［8］WU ZF，SUN XW，WANGCB，et al.Effects of low light stress on rubisco activity and the ultrastructure of chloroplast in functional leaves of peanut［J］.Acta Phytoecologica Sinica，2014，38（7）：740－748.（in Chinese）.

［9］WU ZF，WANGCB，DU LT，et al.Analysis of characteristics and stability of peanut yield in different ecological regions of Shandong Province［J］.Chinese Journal of Eco－Agriculture，2008，16（6）：1439－1443.（in Chinese）.

［10］WANGCB，LIUYF，WU ZF，et al.Diversity and stability of peanut kernel quality in different ecological regions of Shandong Province［J］.Chinese Journal of Eco－Agriculture，2008，16（5）：1138－1142.（in Chinese）.