Abstract
Intensive tillage, high fertiliser inputs, and plastic mulch on the soil surface are widely used by vegetable growers. A field investigation was carried out to quantify the impact of alternate land management and fertiliser practices designed to improve offsite water quality on the productivity of vegetable rotations within a sugarcane farming system in a coastal region of subtropical northeast Australia. Successive crops of capsicum and zucchini were grown in summer 2010–2011 and winter 2011, respectively, using four different management practices. These were ‘Conventional’—the current conventional practice using plastic mulch, bare inter-rows, conventional tillage, and commercial fertiliser inputs; ‘Improved’—a modified conventional system using plastic mulch in the cropped area, an inter-row vegetative mulch, zonal tillage, and reduced fertiliser rates; ‘Trash mulch’—using cane trash or forage sorghum residues instead of plastic mulch, with reduced fertiliser rates and minimum or zero tillage; and ‘Vegetative mulch’—using Rhodes grass or forage sorghum residues instead of plastic mulch, with minimum or zero tillage and reduced fertiliser rates. During the second vegetable crop (zucchini), each management practice was split to receive either soil test-based nutrient inputs or a common, luxury rate of nutrient addition. The ’Trash mulch’ and ‘Vegetative mulch’ systems produced up to 43% lower capsicum and zucchini yields than either of the plastic mulch systems. The relative yield difference between trash systems and plastic mulch management systems remained the same for both the soil test-based and high nutrient application strategies, suggesting that factors other than nutrition (e.g., soil temperature) were driving these differences.
Highlights
The use of plastic mulch on the soil surface is a successful commercial crop production system practiced in several cropping industries [1,2]
Recent studies have reported increased soil organic carbon (SOC) mineralisation under plastic mulch being offset by higher root biomass production [3], providing a neutral effect on soil health while enhancing crop productivity
There were suggestions of nutrient limitations in both management systems without plastic mulch during the capsicum crop, so a common, high nutrient input regime was instigated on the longer sub-block (Figure 1) to test the extent to which nutrient availability may have contributed to the poor productivity of those free-draining systems
Summary
The use of plastic mulch on the soil surface is a successful commercial crop production system practiced in several cropping industries [1,2]. There is strong evidence that this over application of nutrients in vegetable production systems in Australia has the potential to cause adverse environmental impacts through the loss of dissolved nutrients in the water, either via the leaching of excess nutrients to groundwater or the loss of nutrients in surface water runoff [5,8]. Previous studies in the USA [12,13] and more recently in Australia [11] reported the negative environmental impacts of plastic mulch and the advantages of vegetative mulch in inter-rows in terms of reducing runoff and erosion. The regular in-season applications occur from planting up to a week before the last harvest of vegetables This investigation was designed to study the impact of a range of management practices on productivity in intensive vegetable production systems. The impact of these practice changes on water quality and vegetable yield were detailed in Nachimuthu et al [11], while this short communication assesses the impact of increased nutrient inputs as a way of overcoming the observed decline in yield and economic returns of those management practices
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