Comparison of crop water use efficiency with rotation and continuous cropping in an irrigated vertisol

Water use efficiency is a key issue for the Australian cotton industry. For the individual producer the focus is to maximise returns from a limited resource. However, the current debate on allocation of water between domestic, agricultural and environmental sectors, imposes additional significance to water use efficiency at the industry level. We are conducting a project that focuses on crop water use efficiency as a component of whole farm water use efficiency. This will be achieved by (i) identifying the current sources of variation in crop water use efficiency between production units and (ii) quantifying the contribution of rotation and tillage practices to the water use efficiency of irrigated or partially irrigated cotton crops. The aims are three fold..

Changes in some soil properties due to tillage practices in rainfed hardsetting Alfisols and irrigated Vertisols of eastern Australia

Abstract Changes in soil physical and chemical properties were evaluated in several on-farm studies located in rainfed, hardsetting red Al®sols (Ferric Luvisols) and in irrigated, self-mulching Vertisols (Chromic Vertisols) of eastern Australia. The objective of the studies was to evaluate changes in soil physical and chemical properties with time under commercial farming situations where changes had been made to previously used farming systems (native pasture to wheat (Triticum sp.) cultivation in the hardsetting Al®sols; intensively tilled cotton (Gossypium sp.) monoculture to minimum tilled cotton monoculture and cotton± wheat sequences in the irrigated Vertisols). The soil physical and chemical changes in the Al®sols were caused by changing land use from native pasture to intensively tilled wheat cultivation with long fallow and stubble burning, whereas those in the Vertisols were caused by changing from intensive to minimum tillage in cotton-based cropping systems. Indicators of soil physical (tensile strength, structural stability, dispersion) and chemical (pH, electrical conductivity, organic C, total N) quality evaluated in the Al®sols indicated that a signi®cant deterioration in soil quality, which was characterized by an increase in hardsetting behaviour and acidity, and a decrease in organic C, total N and aggregate stability had occurred. These changes were due to inappropriate tillage practices causing soil inversion and the rapid breakdown of organic matter which occurs when intensive tillage practices are imposed in previously untilled soils. In the Vertisols, however, indicators of soil physical (speci®c volume of air-®lled pores in oven-dried clods, plastic limit, soil resilience) and chemical (pH, electrical conductivity, exchangeable sodium percentage, and soil organic C) quality indicated that while deterioration in physical quality (i.e., characterized by an increase in compaction) had occurred, chemical quality had improved. The latter was characterized by an increase in soil organic C and a decrease in exchangeable sodium percentage. These changes were due to replacing intensive tillage with minimum tillage.

Biophysical interactions in tropical agroforestry systems

sequential systems, simultaneous systems Abstract. The rate and extent to which biophysical resources are captured and utilized by the components of an agroforestry system are determined by the nature and intensity of interac-tions between the components. The net effect of these interactions is often determined by the influence of the tree component on the other component(s) and/or on the overall system, and is expressed in terms of such quantifiable responses as soil fertility changes, microclimate modification, resource (water, nutrients, and light) availability and utilization, pest and disease incidence, and allelopathy. The paper reviews such manifestations of biophysical interactions in major simultaneous (e.g., hedgerow intercropping and trees on croplands) and sequential (e.g., planted tree fallows) agroforestry systems. In hedgerow intercropping (HI), the hedge/crop interactions are dominated by soil fertility improvement and competition for growth resources. Higher crop yields in HI than in sole cropping are noted mostly in inherently fertile soils in humid and subhumid tropics, and are caused by large fertility improvement relative to the effects of competition. But, yield increases are rare in semiarid tropics and infertile acid soils because fertility improvement does not offse

Longterm effects of land clearing methods, tillage systemsand cropping systems on surface soil properties of a tropical Alfisol in S. W. Nigeria

The long‐term effects of land clearing methods (manual, shear blade, tree‐pusher/root‐rake combination, traditional), tillage systems (disc ploughing, mechanized no‐tillage, traditional) and cropping systems (annual cropping, alley cropping, graxed pasture) on surface soil physical and chemical properties were evaluated on an Alfisol in south‐western Nigeria ten years after land clearing. Long‐term soil physical degradation was greatest after mechanized land clearing or tillage systems. The erosion resulting from soil compaction with mechanized land management systems resulted in exposure of subsoil. Cropping system had no significant effect on soil physical properties. Alley cropping decreased exchangeable calcium and pH, and increased total acidity mainly through the greater demand for calcium by the hedgerow species. Grazed pasture depleted exchangeable potassium because it was taken up by the grass and exported from the site by the cattle following consumption of the grass

Changes in soil properties of a newly cleared Ultisol due to establishment of hedgerow species in alley cropping systems

This study was initiated to evaluate the short-term (< 3 years) ability of some selected acid-soil adapted hedgerow species when planted in alley cropping systems to improve soil properties in a newly-cleared Ultisol (Typic Kandiudult) of southern Cameroon, 1990–92. The hedgerow species selected were Senna (Senna spectabilis), Flemingia (Flemingia congesta)and Acioa (Acioa barterii). A non-alley-cropped control was also included in the trial. The greatest quantities of prunings, and hence, mulch were produced by Senna and Flemingia. Exchangeable Ca, effective CEC and water infiltration were greatly increased in the alleys of plots where either Flemingia or Senna had been planted within 2•5 years of hedgerow establishment. The large amounts of mulch produced by Senna and Flemingia did, however, result in soil temperatures greater than those of the control or Acioa plots c. 1 year after application of the prunings as mulch. Root growth of Senna in the subsoil was significantly greater than that of either Acioa of Flemingia, but that of cassava was reduced by alley cropping with all three hedgerow species. Compared to the control or alley cropping with Acioa, maize and cassava yields were greater when alley cropped with either Flemingia or Senna hedgerows

Yields of maize/cassava intercrops grown with hedgerows of three multipurpose trees on an acid Ultisol of Cameroon

Maize/cassava were intercropped between hedgerows of Senna spectabilis [(DC.) Irwin and Barneby], Flemingia macrophylla [(Willd.) Merrill] and Dactyladenia barteri [(Hook f ex Oliv.) Engl.] for five consecutive years on an Ultisol in southern Cameroon. Crop yields and hedgerow biomass production in the third to fifth year of cropping are reported. S. spectabilis produced more biomass than F. macrophylla and D. barteri in all years. Cumulative maize grain and cassava tuber yields were highest in F. macrophylla alley cropping, outyielding the no-tree control consistently by 42 to 67% (average 56%). Between hedgerows of D. barteri and S. spectabilis, crops yielded 17% and 16% more than the no-tree control, respectively. However, between S. spectabilis hedgerows, yields were highly variable between years (−15% to +35% compared to the no-tree control) and thus the system is at risk of failure. F. macrophylla is recommended for continuous alley cropping of maize/cassava intercrop. The use of D. barteri may require fallow phases for biomass accumulation followed by cropping phases with rigorous pruning. Although this may lead to lower cumulative yields, the products of the fallow phase, such as stakes and firewood, may provide some compensation