Eleven field trials were sown in the northeastern wheatbelt of Western Australia to test the hypothesis that if wheat cultivars with suitable maturity are sown earlier than current practice, then higher grain yields will be achieved. The experiments included time of sowing treatments that ranged from early May to late June in 1988, 1989 and 1990. Seven commercial cultivars with a wide range of developmental patterns and maturities were used. Sowing between mid May and early June produced the highest grain yields. For plantings after early June, yields declined by approximately 250 kg/ha (15%) per week. Delayed sowing caused a decrease in dry matter and kernel number (per m2). In general this reduction in kernel number was not compensated by an improvement in kernel weight. At early times of sowing, the medium-long season cultivars generally had higher yields than short season cultivars. The short season cultivars were the highest yielding cultivars at the late times of sowing. These results suggest that cultivars should be chosen to suit the seasonal break, which may vary from late April to mid June. As a consequence, farmers should be encouraged to retain a number of cultivars with differing maturities suited to a range of planting times.
The growth and seed yield response of lentil (cv. Digger) to sowing rate (20-120 kg/ha) was studied at 13 sites over 3 seasons in the cropping regions of south-western Australia. The economic optimum plant density was estimated by fitting an asymptotic model to the data and calculating the sowing rate above which the cost for additional seed was equivalent to the revenue that could be achieved from the extra seed yield produced, assuming a 10% opportunity cost. On average across all sites and seasons, only 51% of sown seeds emerged. Increasing sowing rate resulted in greater dry matter production at °owering and maturity, and fewer pods per plant. Harvest index (0·31-0·36), number of seeds per pod (1·13-1·84), and mean seed weight (2·9-3·6 g/100 seeds) remained relatively stable with changes in sowing rate. The asymptotic models fitted to seed yields accounted for 1-73% of the total variance in the data, except at one site where a model could not be found to provide an adequate fit to the data. In addition to this site, another 5 sites were excluded from further consideration where the percentage of variance accounted for was <25% or the predicted optimum densities and seed yield potentials were well beyond the range of the data. The economic optimum of the remaining 7 sites ranged from 96 to 228 plants/m2, with a mean of 146 plants/m2. These results suggest that lentil yields may be improved by increasing sowing rates beyond those currently targeted in southern Australia (100-125 plants/m2). On the basis of these results, targeting a density of about 150 plants/m2 by using a sowing rate of approximately 90-110 kg/ha is recommended, depending on mean seed weight and germination percentage of the seed. Even higher sowing rates may be optimum where the growing conditions are unfavourable and individual plant growth is limited.
An experiment was conducted under controlled conditions in a glasshouse to determine the sensitivity of reproductive development of lentil (Lens culinaris Medikus) genotypes of different origins to water deficit. The 3 genotypes were Cassab (West Asia), Simal (South Asia), and ILL 7979 a crossbred between a West Asian genotype and a South Asian genotype. Two watering treatments, a well-watered control and a water-deficit treatment, were imposed from the beginning of podding. Leaf water relations, total dry matter production, leaf area, and number of flowers, pods, and seeds were measured from podding to maturity. In the well-watered plants the leaf water potential (?leaf) before sunrise ranged from -0.6 to -0.8 MPa. When subjected to water deficit, ?leaf fell to about -3.0 MPa. Genotypes did not show variation in vegetative growth or seed yield under either well-watered or water-deficit conditions, but they differed significantly in the number of flowers, fruiting nodes, pods, and seeds, and harvest index (HI). Seed size in Cassab was 61% larger than ILL 7979 and 105% larger than Simal. The small-seeded genotypes produced the highest number of fruiting nodes and hence a greater number of flowers, pods, and seeds. Seed size was positively correlated with seed growth rate (r = 0.77**) and seed fill duration (r = 0.45*). The water deficit reduced plant height by about 20%, leaf area by 48–81%, and total dry matter by about 60% compared with well-watered plants. The water deficit reduced flower number by 35–46% and increased seed abortion (empty pods) by 17–46%. The water deficit had no effect on the maximum seed growth rate, seed fill duration, or final seed size in any of the 3 genotypes. Therefore, the 70% reduction in seed yield induced by the water deficit was primarily due to a reduction in pod and seed numbers (by 59–70%) rather than individual seed growth rate and seed size.
Chickpea ranks third among pulses in global production with its area expanding in Turkey, Canada and Australia. This crop is broad in adaptation and is widely distributed with its production limited by several biotic and abiotic stresses. It fixes atmospheric nitrogen via a symbiotic relationship with Rhizobium which benefits both chickpea and its following crops. Moisture availability, temperature and photoperiod suitability determine the sowing time for the best yield. Sowing rates range from 40 to 200 kg/ha and sowing depth from 5 to 8 cm for the best yield. Application of mineral fertilizers results in marginal yield increases as chickpea is equipped for acquisition of several minerals from non-traditional soil sources. Weed management is critical favoring the search for improved control measures and genetic sources of herbicide tolerance.. Future genetic enhancements with greater resistance to key biotic, abiotic stresses and herbicides can further improve the sustainability in chickpea production.
Plastic-film mulch is widely used to increase soil temperature and reduce water evaporation in vegetable production. In China, it is also extensively used for growing grain crops, especially in temperature and rainfall limited areas. However, it remains unclear whether the technology is sustainable in terms of maintenance of soil organic carbon (SOC) balance. We assessed the effects of plastic-film mulch on the SOC balance in maize (Zea mays L.) production in a range of cold semiarid environments. We imposed four treatments: (i) no plastic-film mulch or straw incorporation, (ii) plastic-film mulch, (iii) straw incorporation in soil without mulch, and (v) straw incorporation plus mulch, in ridge–furrow prepared fields at five sites along a hydrothermal gradient for up to six years. Maize root biomass across sites increased by 23–38% in mulched plots associated with the increase in aboveground biomass, indicating an increased SOC input, compared to that in non-mulched plots. The plastic-film mulch increased SOC mineralization, indicated by the stimulated decomposition of buried maize straw, and a 4–5% reduction in the concentration of light-fraction SOC (<1.8 g cm−3), but the total SOC concentration and stock in the 0–0.15 m soil layer did not change relative to no mulch after six years of continuous cropping. Plastic-film mulch did not affect the total non-cellulosic sugar content; however, it significantly increased the contribution of microbial-synthesized sugars to the total non-cellulosic sugars, indicating an intensified microbial action on the SOC pool compared to no mulch. Straw incorporation increased the root biomass, light and total SOC concentrations and non-cellulosic sugars, and changed the non-cellulosic sugar composition. We conclude that the increase in soil temperature and moisture by use of plastic-film mulch enhances productivity, but importantly maintains the SOC level in temperature- and rainfall-limited semiarid regions by balancing the increased SOC mineralization with increased root-derived C input.
