Time of Sowing effects on Phosphorus Requirements of two different wheat varieties

Sean Mason1,2, Glenn McDonald2

1Agronomy Solutions Pty Ltd, 3/11 Ridley Street, Hindmarsh SA 5007,
2School of Agriculture, Food and Wine, University of Adelaide, Waite Road, Urrbrae SA 5064

Abstract:

Crop phosphorus (P) acquisition from both soil P reserves and freshly applied P is controlled by climatic conditions that drive soil moisture and temperature. Soil conditions can change significantly across a typical sowing window and therefore this potentially impacts crop P requirements. Phosphorus responses trials performed in broad acre cropping regions of South Australia across two seasons and three times of sowing showed that P requirements can alter across sowing dates and between the two seasons. At the mid-North site in 2017 where starting soil moisture was high, low P rates (0-5 kg P/ha) were required to maximise wheat yields when sown in late April. Comparatively when the P response was assessed at the mid-May sowing time P requirements increased up to 50 kg P/ha which fluctuated slightly with variety. When the trial was repeated in 2018 at a close location with very similar starting soil P levels on marginal soil moisture, P requirements were 38-40 kg P/ha when Mace and Trojan were sown in late April compared to 41-48 kg P/ha for the mid-late May sowing time. This highlights that high starting soil moisture conditions at moderate temperatures can promote P acquisition from soil P reserves which would potentially place less reliance on P inputs. However, if soil moisture levels are marginal there is still a reliance on P inputs. Cooler temperatures associated with later sowing times place a higher demand on P applied as fertiliser.

 

Pulse Phosphorus requirements and impacts on Nitrogen fixation

Sean Mason1,2, Elizabeth Farquharson3,2, Lynette Schubert3

1Agronomy Solutions Pty Ltd, 3/11 Ridley Street, Hindmarsh SA 5007,
2School of Agriculture, Food and Wine, University of Adelaide, Waite Road, Urrbrae SA 5064,
3South Australian Research and Development Institute, Gate 2B, Hartley Grove, Urrbrae, SA, 5064

Abstract:

High commodity prices for several pulse (grain legume) crops over the last five years have meant that crops such as lentil and chickpea have become highly profitable and sowing frequency within rotations has increased significantly in cropping regions of South Australia. Limited information on the nutritional requirements of these pulses has meant that nutrient requirements cannot be calculated based on soil test levels. Recent trials by Wilhelm et al. (pers comm.) have focused on Phosphorus (P) requirements of selected pulses and attempted to determine soil P test critical levels compared to those established for cereals but these trials were not N limited (i.e. N fertiliser applied) and N fixation was thus not considered.

Two P response trials in the Mid-North and central Yorke Peninsula of South Australia investigated the response of lentils and chickpeas to P applications and measured the amount of N fixed with increasing P application. In-season assessments showed higher P requirements for both pulse crops (particularly lentils) compared to wheat. The increase in pulse biomass with increasing P rates coincided with increases in both nodule number but also nodule weight per gram of root. The benefits from optimising pulse production occurred at P rates higher than what is considered district practice for these crops. Dry seasonal conditions meant that the early season increases in biomass didn’t translate to grain in 2018. However, nitrogen fixation estimates (by 15N natural abundance) were highly related to early season nodulation, particularly for lentils.

 

Effect of Organic and Inorganic fertilizer on Premium Rice yield and quality

ABS Sarker1, SS Dipti2

1Principal Scientific Officer, Agronomy Division, Bangladesh Rice Research Institute (BRRI), Gazipur-1701, Bangladesh, sarkerabs@yahoo.com, 2Principal Scientific Officer, Grain Quality and Nutrition Division, BRRI, Gazipur-1701, Bangladesh,

Abstract:

To determine the nutritional needs of Premium Quality Rice (PQR) we compared the effects of inorganic and organic fertilisers on its yield and quality in the Rangpur region of Bangladesh. The organic fertilisers such as Vermi compost and mustard oilcake were compared with recommended fertilizer rate and soil test based fertilizer rate. The experiment was conducted in the July-November rainfed (Transplanted Aman/T Aman) season, and repeated in the November-April fully irrigated (Boro) season. In both seasons the highest yield was obtained in the treatment receiving NPK fertilisers according to soil test recommendations (in 3.7 T Aman and 5.4 t/ha in Boro season). Soil test based fertilizer rate treatment produced higher yield 19% in T Aman season and 86% in Boro season over 4 t/ha vermi compost application treatment. Yields from vermi compost treatments (T6-T9) averaged from 2.48 to 3.07 t/ha in T Aman season but it was 2.9 to 3.8 t/ha in Boro season, and there was no response to increasing rates from 1 to 4 t/ha. There was no detectable difference in yield attributable to mustard oilcake. Rice quality such as cooking and physicochemical properties were unaffected by treatment other than grain protein, which was higher in the NPK treatments. The only rice quality parameters that appear to have been affected. For optimizing grain yield, application rates of NPK chemical fertilisers should follow BRRI recommended fertilizer rates or equivalent rates based on a soil test.

Impact of intercropping soybean and sorghum on shoot production and phosphorus use efficiency in a Vertosol soil

Mortatha Ogee1, Chris Guppy1, Richard Flavel 1 , Graeme Blair1

1 Agronomy and Soil Science, University of New England, Armidale NSW, Australia. gblair@une.edu.au 

Abstract:

A glasshouse study was undertaken of the effect of phosphorus and water interactions on the productivity of intercropped sorghum and soybean grown in a Vertosol soil. Soybean or sorghum were grown alone or mixed. Difficulties in maintaining soil moisture near field capacity resulted in transient waterlogging in the sole soybean treatments which limited aeration in the root boxes. This resulted in reduced N2 fixation with the lowest shoot yields being in inoculated treatments. The shoot dry yield data showed that the growth of mixed soybean with N fertiliser gained a benefit when grown with sorghum, most likely due to a reduction in waterlogging stress as a result of the greater water use by the sorghum. Fertiliser P uptake was similarly affected. Sorghum was more competitive for P fertiliser than soybean when the fertiliser was applied between the plants, but the competition was marginal when the fertiliser was applied beneath each plant.

 

 

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Host

The Australian Society of Agronomy is the professional body for agronomists in Australia. It has approximately 500 active members drawn from government, universities, research organisations and the private sector.

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David Marland Photography david_marland@hotmail.com Graham Centre for Agricultural Innovation, Charles Sturt University

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