Cununurra Clay Research Articles

Potential for irrigated tropical forestry in northern Western Australia

Quote “….the devastated remains of the (ancient) synagogue. All that was left were four walls, and the ribs of a roof. And where once the magnificent sandalwood ark had stood, there was little more than a niche in the wall pointing towards Jerusalem…”. Allan Gold, The Lost Testament. Summary Several high value exotic tropical timber trees have been screened in irrigated species selection experiments, on both predominant soil types (the Cununurra clay and Cockatoo sand), as potential plantation species for the Ord River Irrigation Area (ORIA), northern Western Australia, over the past ten years. Santalum album (Indian sandalwood) has demonstrated potential as a plantation species on the flood irrigated Cununurra clay sites. S. album, a root hemi-parasite, requires a range of host species over its entire rotation length. Consequently, a relatively complex multi-species plantation system has been developed to maintain high plantation productivity. Wood quality issues, plantation policy and environmental implications of irrigated ORIA S. album plantations are also discussed. Damage from Mastotermes darwiniensis prevents long term survival of S. album and many other hardwoods on light textured soils in the region. The re-investigation into the reforestation of these soils has commenced with a range of previously untested species. The early performance of a species selection experiment on a trickle irrigated Cockatoo sand site is presented. At seven months of age Tectona grandis (teak), Ptervcarpus macmcarpus (Burma padauk) and Khaya senegalenesis (African mahogany) exhibit good survival and growth.

Assessing irrigation requirements in the Ord Sugar Industry using a simulation modelling approach

Summary. Sustainable irrigation guidelines that maximise profitability and minimise water losses and accession to the watertable are required for the new Ord Sugar Industry. In addition, knowledge on crop water requirements is needed to guide water allocation and costing policies for the expanding Ord Irrigation Area where sugarcane is likely to be a dominant crop. Field data indicating water requirements for sugar in the Ord Irrigation Area are few and this paper deploys a modelling approach to extrapolate from knowledge of water requirements in other parts of the world. The approach links long-term climatic data with soil water characteristics of the main soil type, with a cropping systems model, to develop indicative estimates of irrigation water requirement and yield consequences for different management options for sugarcane production in the Ord. Analyses of the growth of 12-month old ratoon crops were conducted using the APSIM–Sugarcane model with historical climatic data from 1960 to 1985 and either a deep (188 mm available water to 160 cm depth) or shallow (144 mm of water to 120 cm depth) Cununurra clay soil. Under maximum attainable growth conditions where crops were irrigated after half the soil water supply was depleted, average sucrose yield ranged from 26.7 to 29.0 t/ha, and the irrigation requirement (assuming 100% application efficiency) ranged from 22.7 to 23.8 ML/ha depending on ratooning date. Soil water holding capacity had a major effect on the number of irrigations and the interval between irrigation for a given irrigation schedule but little effect on yield or irrigation requirement. Varying the irrigation schedule by changing the level of soil water depletion before irrigation and thus the irrigation frequency, showed the tradeoff between yield and irrigation requirement with the most profitable irrigation schedule depending on the price of sucrose and the cost of irrigation relative to other costs. Most of the year-to-year variation in irrigation water requirement could be explained by the highly variable effectiveness in soil storage of rainfall which ranged from 44 to 93%. This study has provided insight and indicative estimates of the yield and irrigation requirements for different irrigation management options for use in the establishment of an Ord River sugar industry. These estimates will be further refined as field data become available.

Phosphorus nutrition of large-seeded chickpea cv. Macarena (Cicer arietinum) in the Ord River Irrigation Area, Western Australia

The phosphorus (P) nutrition of largeseeded chickpea (Cicer arietinum) cv. Macarena grown on Cununurra clay in the Ord River Irrigation Area was studied in field trials and by sampling commercial crops. Response to applied and residual P on a previously uncropped site (site 1) was examined over 2 growing seasons and to applied P on a site with a history of cropping (site 2) in 1 season. At site 1, yield increased with application of up to 50 kg P/ha in the first year and 100 kg P/ha in the second year. There was no significant response in the second year to the P applied in the previous season, probably because of rapid fixation of P in Cununurra clay. At site 2, with a residual soil P level of 24 �g/g (HCO3), no growth response to applied P was observed. The survey of commercial crops included determination of P in soil, foliage, and seed, and the recording of phosphatic fertilisers applied. The data indicate that excessive P fertiliser is applied to many chickpea crops, with only a few crops being inadequately supplied.

Sulfur deficiency in rice grown on the alkaline soils of the Ord Irrigation Area, Western Australia

Nutrient and acidification effects of sulfur (S) on the growth of flooded rice on Cununurra clay from the Ord Irrigation Area, Western Australia. were studied in pot experiments. An acute S deficiency in the surface horizon of Cununurra clay was found. This deficiency was extreme on virgin soil but was also evident on cropped soil that had received substantial amounts of S as superphosphate and ammonium sulfate in the past. The major effect of an application of elemental S on rice growth was as a nutrient. Irrigation water appears to be an important source of nutrient S in this remote area where annual atmospheric accessions of S are estimated to be about 1 kg ha-1. The S content of Ord irrigation water from Lake Argyle is relatively low (mean � s.e. sulfate3 = 1.7 � 0.05 mg L-1) by world standards. Nevertheless. in this study, 62% of the S added with the Ord irrigation water was recovered in the plant tops. This indicates that factors which determine the amount of irrigation water applied are likely to affect the field incidence of S deficiency. In particular, decreased usage of irrigation water during the December-March wet season (when average rainfall is 630 mm) may increase the likelihood of S deficiency in rice.

Nitrogen contributed by grain legumes to rice grown in rotation on the Cununurra soils of the Ord Irrigation Area, Western Australia

The uptake of nitrogen (N) by dry season rice following wet season crops of soybean (for grain or green manure), green gram, Sesbania cannabina (a native legume), a cereal (sorghum or dryland rice for grain), or bare fallow, was studied for 3 cropping cycles over 4 years. The work was done on Cununurra clay (0.04% N) at Kimberley Research Station near Kununurra, W.A., in the Ord Irrigation Area. Stubbles were returned to the soil except in the first cycle when (excluding the green manure treatment) all tops were removed from the plots at maturity. There was a 12-month bare fallow period between the first and second cycles. Dry season rice was drill-sown with or without 100 kg ha-1 of N applied as urea at permanent flooding. Soybean, green gram and Sesbania crops accumulated 290-360, 80-130 and 110-180 kg N ha-1, respectively, in the tops at maturity. An average of about 40 kg N ha-1 was present in the stem bases and roots (0-20 cm depth). Estimates of nitrogen fixation based on 15N dilution measurements ranged from 65-72% of total plant N when the legumes were grown after 12 months fallow, to 93-95% when they were grown immediately following dry season rice. Fertiliser N at 25 kg ha-1 applied presowing ('starter' N) had no significant effect on legume N yield at maturity. N returned in leaves, stems and hulls averaged 30, 50 and 80 kg N ha-1 for green gram, soybean and Sesbania, respectively. Rice grain yields and N uptake at maturity were generally highest after Sesbania and lowest after a wet season cereal crop. Differences among treatments were small and related to the quantity of N returned in residues. On average, 11% of the N in the residues was recovered in the tops of the following rice crop. Rice yields increased over the 4-year period, but mean increases were similar for legume and non-legume treatments. The average apparent recovery of N applied as urea to dry season rice at permanent flooding was 76%. The inclusion of a soybean cash crop in the rotation offers the possibility of a marginal reduction in the need for N fertiliser.

Response of irrigated soybeans (Glycine max) to phosphorus on an alkaline cracking clay in semi-arid tropical Australia

The primary and residual effects of phosphorus (P) fertilizer on soybeans (Glycine max cv. Buchanan) were studied at one site for three seasons on Cununurra clay in the Ord Irrigation Area. Grain yield increased (P< 0.01) with both primary and residual P in all seasons. When grain yields over the 3 years were standardized to eliminate seasonal effects, relative grain yield (RGY) was positively related to each of bicarbonate-extractable soil P (EP), applied fertilizer P (FP) and fertilizer P applied to the previous crop (PFP). Seventy-three per cent of the variation in relative yield within years could be explained by the equation: RGY = 45.44 + 0.64FP + l.84EP + 0.197PFP R 2 = 0 . 7 3 , P < 0.01 Increasing P status was associated with increased plant height, dry matter production and weight of 100 seeds and increased the number of main-stem nodes, nodules, pods per plant and days to maturity, but had no effect on number of seeds per pod and number of days until commencement and completion of flowering. Concentrations of P in the whole tops and uppermost leaf increased with increasing rate of P application. However, there was a significant P x growth stage interaction on nitrogen concentrations in whole tops and upper-most leaf, these being lower in the high-P plots early in the season. Grain protein content increased with increasing P status while oil content was reduced. The results show that rates of P application higher than those being currently used are required to maximize soybean yield on Cununurra clay.

An analysis of the environmental limitation to yield of irrigated grain sorghum during the dry season in tropical Australia using a radiation, interception model

Variation in yield of irrigated grain sorghum (Sorghum bicolor L. Moench) grown during the dry season in tropical Australia was analysed in terms of the amount of photosynthetically active radiation (PAR) intercepted, its efficiency of use in dry matter production and the proportion of dry matter partitioned to grain. Three commercial hybrids (Texas 610SR, Dekalb DK55, Pacific Monsoon) grown under favourable conditions on two soil types (Cununurra Clay and Ord Sandy Loam) yielded similarly, but there was a significant effect of sowing date. Grain yield was highest (9.5 t ha-1 at 14% moisture) in the May sowing, with the lowest yield (7.4 t ha-1) being obtained in the April sowing. Yield was intermediate from a July sowing. Differences in grain yield across the dry season were not related to the amount of PAR intercepted, nor to the efficiency of conversion of intercepted PAR into net aboveground dry matter, but rather to differences in dry matter partitioning. A stable efficiency of conversion of 2.4 g MJ-1 of intercepted PAR was recorded for the entire crop cycle for sorghum crops growing under favourable growing conditions in this environment. This conversion efficiency for a tropical C4 cereal is similar to maximum values, but higher than average conversion efficiencies over the entire crop cycle obtained for temperate C3 cereals growing in temperate regions. Temperature did not affect this conversion efficiency, but had a pronounced effect on the duration of crop development.

Residual values of zinc sulfate and acidifying (elemental) sulfur for rice on the alkaline Cununurra soils of the Ord Irrigation Area, Western Australia

The residual values of zinc sulfate and acidifying (elemental) sulfur (S) for rice on Cununurra clay were investigated at Kimberley Research Station, near Kununurra in the Ord Irrigation Area, Western Australia. Successive crops were grown on 2 sites showing different degrees of zinc (Zn) deficiency according to visual symptoms. Despite the marked response to Zn fertiliser shown by the first crop of IR665-24-1 rice on the more deficient site (previously fallow for 12 months) there was no significant yield response to applied Zn in the third crop. On the less Zn deficient site (previously under weeds for several years), IR661-1-170-1-3 rice showed no response to Zn fertiliser although transient symptoms occurred in the first and second crops. Continuous cropping per se apparently reduced the severity of Zn deficiency on both sites, thus negating attempts to estimate the residual value of Zn fertiliser. The 2 sites were not distinguishable by the EDTAammonium carbonate soil test for Zn. Extractable Zn increased with increasing level of Zn fertiliser, but plant response was not related to extractable Zn. Application of elemental S (1-4 t ha-1) had no effect on extractable Zn levels before sowing of rice. Increased rice yields due to acidifying S were confirmed, but the residual effects did not extend beyond the fourth crop. In each of the 3 seasons following S application, the yield of IR661-1-170-1-3 increased by 0.3-0.6 t ha-1 but, at current prices, the use of S as a soil ameliorant for rice in the Ord Irrigation Area would be uneconomic.

Fate of urea nitrogen applied at planting to grain sorghum grown under sprinkler and furrow irrigation on a cracking clay soil

Uptake of nitrogen (N) fertilizer and yields of grain by sorghum on Cununurra clay in north-western Australia have been found previously to be higher under sprinkler than under furrow irrigation. The cause of this was investigated using a 15N balance technique on field microplots. Additional data on sequential changes in the distribution of mineral-N in the soil, and on volatilization of ammonia, were collected from outside the 15N microplots. The improved effectiveness of N fertilizer under sprinkler irrigation was associated with less upward movement of 15N into the top of the ridge and thus out of the rooting zone of the crop. Furrow irrigation caused 22% of the 15N applied to move into the top of the ridge, sprinkler irrigation caused only 2% of the 15N to do this. The urea appeared to move upwards during the first irrigation, and this N became unavailable to the sorghum because of soil dryness, high temperatures, and osmotic effects in the surface soil. Loss of 15N from the soil-plant system was approximately 27% under both systems of irrigation. This loss was attributed to denitrification, because there was no evidence for large losses of N by leaching or volatization of ammonia.

Pattern of infiltration with furrow irrigation and evapotranspiration of kenaf (Hibiscus cannabinus) grown on Cununurra clay in the Ord Irrigation Area

The infiltration characteristics of Cununurra clay, the dominant soil in the Ord Irrigation Area, were examined in a furrow-irrigated experiment with kenaf. The irrigation treatments, which were scheduled on leaf water potentials at dawn and solar noon, ensured that water was applied over a wide range of soil moistures. Flowmeters were used in the supply and drainage channels, and the difference between the flows in these meters was taken as the amount of water infiltrating the soil. The efficiencies of application ranged from 50 to 85% and were inversely related to the frequency of application because the infiltration rate on this heavy swelling soil declined with increasing soil moisture content. Crop water use patterns of kenaf in this semi-arid tropical environment were also determined. Evapotranspiration was estimated from the changes over time in soil moisture in the profile. Clear patterns were established for the changes in the ratio of evapotranspiration to free water evaporation with growth under soil moisture regimes ranging from almost stress-free to severely stressed. A peak value of 1.52 was recorded for the period 14-1 6 weeks after sowing in the most frequently watered treatment.

The use of leaf development rate to determine time to irrigate pangola grass

The leaf development rate (LDR) of pangola grass (the number of new leaves produced on a shoot per unit of time) growing in swards on Cununurra Clay in the Ord Valley was found to decline linearly with cumulative net pan evaporation (+Ep) and ceased at a +Ep of 201 mm. The LDR of vegetative shoots, which have hairy nodes, was 3-5 times greater than that of reproductive shoots, which have glabrous nodes. Nitrogen increased the LDR of only the reproductive shoots. Vegetative shoots were preferred for measuring the response of pangola grass to moisture stress because of their insensitivity to nitrogen fertilizer level and faster LDR. Moisture availability (M) was calculated for each day as follows: M = 201 -+Ep for +Ep < 201, or otherwise M = 0. In an irrigation trial covering two 3-month periods there was a linear relation between M and dry matter yield within each period, and at each of four N rates. It is suggested that LDR measurements could be used to determine irrigation frequency of pangola grass for any site where pan evaporation is also measured. On Cununurra Clay in the Ord Valley the most frequent irrigation schedule (every 2 weeks) gave the highest dry matter yields.

Effect of sulphur, sulphuric acid and gypsum on the yield of rice on the Cununurra soils of the Ord Irrigation Area, Western Australia

A field experiment was conducted at Kimberley Research Station near Kununurra, Western Australia, to compare elemental sulphur, sulphuric acid and gypsum as soil ameliorants for drill-sown rice on the Cununurra clay of the Ord Irrigation Area. The application of sulphur (0.5-4 t ha-1) and concentrated sulphuric acid (800-1 600 1 ha-1) to Cununurra clay temporarily decreased soil pH, improved seedling establishment and increased the mean grain yield of Bluebonnet 50 and IR661-1-170-1-3 rice from 4.27 to 5.32 t ha-1. Plant growth during the first 6 weeks was better and the transient iron chlorosis, which often develops after permanent flooding, was largely eliminated. Gypsum (1-4 t ha-1) had no significant effect on soil pH, seedling establishment, early growth or grain yield. Mean pH of the flooded soil (0-5 cm) one month after permanent flooding was 6.60, 6.56, 6.07 and 5.52 in the untreatad, gypsum, sulphur and sulphuric acid plots, respectively. Mean grain yield increased linearly as the pH of the flooded soil (0-5 cm) one month after permanent flooding decreased over the range of 6.5-5.5. The pH values of air dried soil samples takgn at 3, 6, 9 and 11 weeks after sowing and determined at the saturation moisture content fell by 0.5 to 2 units after the addition of sulphur and sulphuric acid. The decrease in pH at 3 weeks after the application of 800 l ha-1 sulphuric acid was five times greater than that due to an equivalent amount of elemsntal sulphur, but the effect of the acid was short-lived. Calcium and magnesium concentrations in the saturation extracts of the air-dried soil samples taken at 3 and 6 weeks after sowing were increased by the application of sulphur and gypsum. All ameliorants increased the nitrogen concentration in the plant tops at 3 weeks after sowing but only sulphur and sulphuric acid increased phosphorus, potassium, manganese, zinc or iron concentrations at one or more sampling dates.

Ecological aspects of weed control in cotton in the Ord River valley, W.A. 2. The effect of soil depth on emergence of weed seedlings

A study was made of the emergence from various soil depths of cotton, six grasses and six broad-leaved weeds commonly occurring in the irrigated area of the Ord River valley, W.A. The experiments were conducted in a glasshouse under temperatures fluctuating between 20� and 35�C, under conditions of adequate aeration and soil water in Cununurra clay, the main soil type of the Ord irrigation area. Seedling emergence was inversely related to seed depth, and, in general, the ability of seeds to emerge from various soil depths was positively associated with the average seed weight of the species. Of the grasses, only Echinochloa colonum and Iseilema vaginiflorum emerged from depths exceeding 3 inches. The maximum depths from which broad-leaved species emerged varied from 3 to 7 inches, depending on the species. The emergence pattern of cotton was almost identical with that of Hibiscus ficulneus and Operculina turpethum, but cotton and Operculina were the only species to emerge from a depth of 7 inches and then only in small numbers. The practical implications of these findings on depth of cultivation and herbicide placement are discussed.