Productivity and water relations of field-grown cashew: a comparison of sprinkler and drip irrigation

Abstract

Cashew is an emerging crop in the seasonally 'wet-dry' tropical regions of northern Australia. In North Queensland flowering and fruiting of cashew coincides with the dry season (May-November). During this period growers sprinkler irrigate at 500 L/tree.week. A 3-year (1996-98) experiment compared this strategy with alternatives, including no irrigation or drip irrigation in which 115 or 230 L/tree.week was applied by drippers placed near the tree trunk and near the canopy drip line throughout the dry season. Measurements of soil water to 1.3 m, leaf gas exchange, chlorophyll fluorescence, tree sap flow and yield were made. Data collected in the first 2 years showed that the water requirement of the trees increased progressively as the crop load and evaporative demand increased during the dry season. During the final year of the study, additional sprinkler and drip treatments, in which water applications were progressively increased during the dry season, were introduced.The productivity of cashew in this experiment was strongly influenced by irrigation treatments, ranging (over all years) from 42 to 160 g nut/m 2 canopy surface area. Depletion of plant-available water in the root zone was associated with a reduction in photosynthesis mediated by partial stomatal closure. These effects of soil drying were evident in all irrigated treatments during the mid and late stages of the dry season but were more severe in treatments receiving the least water. When irrigation was withheld until the mid-stage of the dry season the trees had similar yields to those that were irrigated throughout, emphasising the importance of providing adequate irrigation between nut set and harvest.When rainfall from January to September in each year of the study was taken into account, there was a strong linear relationship between nut yield and water applied (rainfall + irrigation), with each extra kilolitre of water applied resulting in about 6 extra g nut/m 2 canopy surface area. This linear relationship was based on water application in the range 25-50 kL per season. It is possible that if the seasonal water application had exceeded 50 kL the marginal response to extra water may have diminished. Using drippers was slightly more efficient than sprinklers, with drip-irrigated trees requiring about 5% less water applied to achieve a given nut yield.In years when rainfall is average, and subject to other economic factors, growers in North Queensland should aim to irrigate about 500 L/tree.week. In years of low rainfall between January and September it is likely that yield will be improved by applying more irrigation water; high rainfall during these months of the year may reduce the irrigation requirement. In all cases growers should be careful to accurately monitor water applications, particularly when the total (from rainfall + irrigation) exceeds 40 kL/tree for the season.

Phenotypic Stability Analysis of Yield Components in Cashew (Anacardium occidentale L.) Using Additive Main Effect and Multiplicative Interaction (AMMI) and GGE Biplot Analyses

“…Climatic data (not shown) showed that each environment (location) varies in rainfall (quantity and pattern), temperature, humidity, sunshine (spread and quantity), and harmattan (very dry and dusty wind), all of which could affect cashew flowering and fruiting differently. The effect of climatic and edaphic factors on flowering and yield of some tree crops are well documented (Gordon 1976;Ohler, 1979;Avim and de 1984;Esan 1993;Blaike et al 1998;Tolla 2004;Omolaja et al 2009;Omonona and Akintude 2009;Oyekale et al 2009). However, among the three locations, Ibadan and Uhonmora favour flowering precocity.…”

THE WATER RELATIONS AND IRRIGATION REQUIREMENTS OF CASHEW (ANACARDIUM OCCIDENTALE L.): A REVIEW

“…BLA 273), Blaikie et al . (2001) recorded sap flows between 20 and 25 L d −1 tree −1 (when evaporation rates from a USWB Class A pan were about 4 mm d −1 ), regardless of the irrigation treatment. Differences between irrigation treatments became clearer, despite large tree-to-tree variability, later in the season when evaporation rates had reached 9 mm d −1 .…”

“…Then for every cubic metre of irrigation (or rain) applied above this base level, there is a yield increase of about 6 g m −2 . Kernel recovery (the proportion of the nut weight made up by the kernel) averaged about 33% across all treatment combinations (Blaikie et al ., 2001).…”

“…The experiment in north Queensland described above included a comparison between sprinkler (not specified, presumed to be under-tree micro-sprinklers) and drip irrigation, as well as several irrigation treatments (Blaikie et al ., 2001). Similar linear functions between yield and water applied were derived when the two irrigation methods were analysed separately, but with different slopes (sprinkler + 5.24 X; drip + 7.45 X).…”

Actual evapotranspiration estimation by ground and remote sensing methods: the Australian experience

“…On the other hand, Takahashi et al (2003) found that Eucalyptus camaldulensis trees extracted most of its water from the top meter of the soil profile, indicating the plasticity of this genus to different hydrological regimes. Sap flow sensors have also been used to monitor water use of woody agricultural crops, including grapevines (Yunusa et al, 1997) and cashew (Blaikie and Chacko, 1998;Blaikie et al, 2001). and Doody et al (In preparation) recently quantified water use by willows growing on Australian riverbanks and within streams.…”