Research On Productivity And Phosphorus Untilization Charateristics Of Wheat/Maize/Soybean Relay Strip Intercropping System

Wheat/maize/soybean (W/M/S) relay-intercropping system has been evolved the mainly dry land farming mode in Sichuan province, study on productivity and soil nutrient changes for high productivity high nutrient efficient and nutrient scientific management for this system is important. The W/M/S relay-intercropping system and corresponds sole crops as study object, field experiment was carried out in 2011-2013, with 5 phosphate (P) application rates (Wheat:0,20,40,60,80 kg P ha-1, marked as WP0、WP1、WP2、WP3、WP4; Maize:0、16、32、48、64 kg P ha-1, marked as MP0、 MP1、MP2、MP3、MP4; Soybean marked as SP0、SP1、SP2、SP3、SP4) to study on crops productivity, dry matter accumulation translation, nutrient use efficiency and soil nutrient content diversification, compared the productivity, nutrient use efficiency and soil nutrient changed among relay-intercropping sole and rational systems. The results showed that:(1) Three years average yield of intercropping wheat from WP0 to WP4 treatments increased 23.9%、24.2%、26.1%、23.9% and 36.8% compared with sole wheat, the yield advantage for intercropping wheat increased by increasing P application rate. Border rows contribute 60% for intercropping wheat yield and higher than 46.3% compared with sole wheat. Intercropping wheat dry matter accumulation before flowering stage transport to seed was significantly higher than sole, but with increase P application rate did not increase dry matter accumulation before flowering to seed contribution rate. Intercropping wheat uptake more nitrogen (N), P and potassium (K) nutrient than monoculture, nutrient accumulation increase with P application increasing reduced after the first increase. The critical P application level for intercropping and sole yield were 50 kg P ha-1 and 40 kg P ha-1, respectively, and The critical P application level for intercropping and sole P uptake were 50 kg P ha-1 and 40 kg P ha-1, respectively.(2) The linear-plateau model described the relationship between P application rate and yield well (R2=0.76**), the change point was 32 kg P ha-1 and the highest yield was 6.19 Mg ha-1, further P increasing led no yield increased. With increased P application rate maize shoot biomass increased significant at seeding stage, but al mature stage the maize shoot biomass has a first increase and then decrease. Dry matter transport from before flowering stage to seed increased with more P application rate, the well P application point were 32 kg P ha-1 to 48 kg P ha-1. With 48 kg P ha-1 application rate maize N, P, K input/uptake ratio were 1.76、1.91、1.09, respectively, and with 32 kg P ha-1 application rate the correspondence date were 1.83、 1.31、1.10.(3) With increasing soil Olsen-P the intercropping and sole soybean yield have a first increase then decrease, intercropping on average than sole 34.8%. Intercropping soybean yield led not any increase with more than 10 mg kg-1 soil Olsen-P content, but the soil Olsen-P content between 0-27 mg kg-1 sole soybean yield increase with increased soli Olsen-P content. When soybean intercropped with maize the growth rate was 12.10 kg ha-1d-1 low than sole 13.5%, but in the recovery period intercrpping growth rate higher than sole 34.7%. Intercropping soybean HI higher than sole, and with increasing soil Olsen-P the sole HI was decrease. The nutrient uptake and dry matter accumulation have similar development for intercropping and sole soybean, but stem and leaf N, P, K uptake of sole increased with increasing Olsen-P higher than intercropping. Monoculture soybean P absorption phenomenon of luxury.(4) W/M/S on average yield more than wheat-soybean (W-S) 2.842.84 Mg ha-1, higher than sole crops 36.5%. A change-point was observed in relationship between P application and yield, the critical level of P and yield for W/M/S was 71.5 kg P ha-1 (Maize 32 kg P ha-1, wheat-soybean strip 40 kg P ha-1), for W-S was 43 kg P ha-1, for sole crops was 93.3 kg P ha-1. The apparent P recovery efficiency (APRE) decreased with increasing P application rate, at P2 treatment W/M/S APRE was 28.0% and apparent P balance (APB) was -0.5 kg P ha-1, W-S correspondence date was 25.5% and -34.7 kg P ha-1.. Planting patterns did not significantly alter the wheat, maize, soybean physiological P use efficiency, with an increase P application crops PHI declined, the ratio of PHI/HI intercropping below monoculture.(5) Soil P content changed with P applied both in intercropping and monoculture system, at P0、P1 treatment soil Olsen-P in the top layer decreased year by year and at P3、P4 treatment the values increased, only at P2 treatment the date not changed for years and maintain at 20 mg kg-1 level. P fertilizer mainly accumulation in the top 20 cm layer, at P3、P4 treatment soil total P content increase 0.11 and 0.15 g kg-1 yr-1. Soil nitrate of intercropping less than monoculture, with increasing P application rate the soil nitrate decreased. The critical levels of total P and Olsen-P was 0.55 g kg-1, Olsen-P and CaCl2-P was 40 mg kg-1, soil Olsen-P and wheat, maize, soybean yield were 12.6、16.5 and 8.8 mg kg-1, respectively.Above all, With a rational P management strategies and application rate in W/M/S relay intercropping system could maintaining a steady soil Olsen-P level, have a high crop yields and a high apparent P recovery efficiency. These P management strategies may provide a reference for nutrient management in intensity agricultural areas.