The efficiency of pastures and forage crops in photosynthetic conversion of solar radiation in the Waikato District, New Zealand

Abstract

The theory underlying the estimation of potential yield of herbage is briefly discussed, and an analysis of yield data in relation to this potential in terms of conversion efficiency (C.E.) is presented for the Waikato district in New Zealand.On an annual basis irrigated pastures usefully convert approximately 0.60% of incident energy (10% of estimated potential) compared with overseas evidence of C.E. in excess of 2% in cereal crops and highproducing grasses grown without supplemental water. Similar varieties grown in this district without irrigation seldom approach this level of production, and, in general, show little if any real increase in C.E. relative to that of irrigated pastures.Winter greenfeed species with C.E.s ranging from 0.60%-D.70% perform much better than permanent pastures during winter, but net gain in yield is not large.

IX. Hamilton

“…Only 46% of the variation in summer growth in the present trial was explained by restricted soil moisture supply (Baars & Coulter 1974), and even on irrigated pastures consisting of cocksfoot, ryegrass, and white clover, a constant decline in growth rates was recorded after December (Weeda 1965). Noble (1972) found that in spite of adequate light the conversion efficiency of solar energy is low in the Waikato on both irrigated and unirrigated pasture. Consequently it can be concluded that the high summer temperatures inhibit pasture growth in the Waikato.…”

Designing the Crops for the Future; The CropBooster Program

“…The key to achieving the future required global crop yield increases will be developing advanced crops with increased photosynthesis, which is the major yield-related plant trait that can still be substantially improved [17,18]. Currently, in temperate agricultural crops, the overall long-term efficiency of conversion of absorbed solar radiation to the energy content of biomass (ε c , a parameter in the Monteith model for crop productivity [17]) is approximately 0.5-1.3% [19][20][21] implying that for food production we miss around 99% of the available solar energy. Growth season estimates of ε c are higher, at about one-third to one-half of the theoretical maximum efficiencies for solar energy conversion, which on a total solar irradiance basis are about 4.5% for C3 and 6% for C4 crops [22].…”

The relationship between solar radiation, soil water, and water potential of ears of wheat

“…Data on solar radiation obtained at the experimental site should be more satisfactory for these uses, which involve essentially short-term events. Noble (1972), however, notes that it is generally accepted that, for long-term applications, radiation data can be used for sites up to 80 km from the recording station provided there is no major topographically-induced change in the local climate. Possibly an even more closely fitting equation would have been derived if water potentials were related to net radiation over the crop.…”