Field Research & Agronomy

Phosphorus and potassium rates in lupins on sandy soil

AIM

To assess the value and to determine the optimal rates for applying P and K fertilizer to lupins on sandy soil in the Mingenew area. This will also help to improve the advice given to local farmers when making their fertilizer decisions.

For further details contract your local Area Manager or the Summit Research Team

CONCLUSIONS

• NDVI data shows a strong and significant growth response to P application and an insignificant decreasing trend when K is applied.
• The harvest data demonstrated that there was a statistically significant yield response to P and no response to K.
  The highest yield was 2.94 t/ha which received 20P and 10K. The lowest was 2.27 t/ha from 0P and 40K. P application saw a notable and beneficial increase in lupin yield, with a 12% increase from 10P, and a 21% increase from 20-30P when compared with 0P.
• Even though plant biomass was considerably less at higher K rates earlier in the season, this decrease did not express as strongly in yield.
• The decrease in plant growth and yield with higher rates of K can be attributed to the sensitivity of lupins to the salt effect of MOP (KCL) in drying soils.
• Based on gross margin calculations and response curves the optimum rate for applying fertilizer to lupins under these conditions is 20 kg/ha of P and 10 kg/ha or less of K.