Facilitating enhanced peanut / sugarcane rotations by assessing and managing the issues related to growing peanuts : SRDC Grower Group Innovation Project final report

Abstract

Rotation cropping has been identified by the Sugar Yield decline Joint Venture (SYDJV) as a critical tool in addressing decline in the Australian sugar industry. Previous research demonstrates that when break crops are combined with correct row spacing, GPS guidance and minimal cultivation they can be powerful tools in addressing yield decline. Producers on sandy soil have found that the nematode controlling effects of growing peanuts as a break crop is more beneficial than other legumes. The industry standard for peanut production in cane based farming systems involves a number of cultivations. There is ample evidence demonstrating that cultivation is detrimental to soil biology and structure. This body of evidence was at the heart of the members of SSPag when they decided they wanted to try to grow peanuts in an uncultivated cane trash blanket. That was our aim. In order to achieve our goal we sought and received support from SRDC to conduct the trial work necessary. The trial included a Factorial Randomized Area as part of a 3.3ha site. The randomised area was comprised of three tillage regimes (conventional, reduced and zero) by two fertiliser treatments (nil and 100kgN/ha supplied as urea) with four replicates. Each experimental unit consisted of three 1.83m beds by 20m row length. The trial was implemented in a third ratoon paddock of Cv. Q188 that had been grown on 1.83m beds with a dual row configuration under green cane trash blanket. The whole area was treated with Lime @ 3t/ha and Dolomite @ 1t/ha applied to the trash surface. The main trial area was fertilised as dictated by soil testing but the nitrogen component was modified in the randomised trial area. A literature search made us believe that we needed to rip under the peanut row to alleviate the compaction caused by the cane harvesting equipment. This was done using a coulter and Yeoman ripper in all areas except the zero till plots. The conventionally cultivated plots were cultivated by rotary hoe in addition to the ripping. The soil was quite moist for the ripping process and not all the ripper tracks closed in even after the application of a waisted roller. The peanuts were planted using an inclined plate seed meter and “Day Break” single disc opener. The seeds were dusted with inoculant before being loaded into the planter.. The strike was slow and uneven because of a number of issues. The most critical was the failure of the disc to cut the trash cleanly resulting in the seeds being enveloped by trash causing poor soil to seed contact and therefore poor and slow germination and failure of the inoculant due to drying out Another issue was the open ripper marks saw some seeds going deep into the soil and only emerging some weeks later. The results at harvest were best in the conventional system with the zero till being the worst. Only the conventional system produced a viable result. The addition of the nitrogen had a positive effect in all cultivation regimes. The cane crop following the peanuts saw a not statistically significant effect, that the conventionally cultivated plots were most productive and the zero till the least productive. It should be noted here that no fertiliser at all was added to grow the cane crop in the rep area because we thought this would even out the resulting cane crop. This was probably true as the plots that had the N added to the peanut crop outperformed the plots that had no N added to the peanut crop. In some areas of the bulk area of the trial we fertilised the crop as is the normal practice and did not fertilise in other areas. At harvest it was determined that the unfertilised sections were less productive but more profitable when taking into account the cost of the applied fertiliser. Overall the project alerted us to the need for a purpose built planter that would be able to successfully plant peanuts through the trash blanket. We applied to SRDC for support for this and were successful in gaining funding and building the planter. The results of this project GGP040 is available through SRDC.