Dryland Treatment Research Articles

Plant Water Relationships of Spring Wheat as Influenced by Shelter and Soil Water1

AbstractField windbreaks have been planted primarily for soil erosion control; subsequently, research has shown that windbreaks have an effect on microclimate and on growth and yield of crops. Other research has shown that plant water relations respond to changes in microclimate. The present work was undertaken to determine the effect of microclimate changes induced by a slat‐fence windbreak on the plant water relations of field‐grown wheat (Triticum aestivum L.). Slat‐fence barriers were used as windbreaks for studying effects of shelter‐modified microclimte on plant water relations of ‘Waldron’ spring wheat, grown on Parshall fine sandy loam (Pachic Haploboroll), under irrigated and dryland soil water regimes. Data were collected on leaf water potential (Ψl), xylem water potential (Ψx), stomatal diffusion resistance (rs), canopy temperature (Tc), soil water potential (Ψs), soil water extraction, and grain yield.Plant water status of the wheat crop was strongly affected by shelter and soil water content. The treatment combination of shelter plus irrigation produced a higher Ψl and lower Tc and, overall, was the most beneficial treatment in creating a favorable plant water status. The dryland treatments were under considerable water stress from early heading to maturity. The presence of the shelter did not alleviate the water stress on the dryland‐grown plants. Water‐use efficiency was significantly higher for the irrigated‐sheltered as compared with the irrigated‐exposed treatments. Water‐use efficiency of the dryland treatments was lower than the irrigated treatments, but the dryland treatments did not differ from each other. The results of our study indicated that windbreaks will be most beneficial to a wheat crop only if soil water is adequate for good crop growth throughout the growing season. Because soil water varies considerably from year to year in the northern Great Plains, crop responses to windbreaks can also be expected to vary considerably.

Tillage Effects on Winter Wheat Production where the Irrigated and Dryland Crops are Alternated1

AbstractWhile adequately irrigated winter wheat (Triticum aestivum L.) yields are relatively high, drylamd wheat yields in the southern Great Plains are only about 700 kg/ha with continuous cropping and about 1,000 kg/ha on a harvested‐area basis after fallow. This study was conducted to determine if yields could be increased where irrigated and dryland wheat crops are alternated on the same plots. Tillage effects were also studied.In this study, continuous winter wheat production was evaluated with respect to grain and residue yields and soil water storage, use, and use‐efficiency. Wheat crops were alternately grown on Pullman clay loam [fine, mixed, thermic family of Torrertic Paleustolls (Mollisols)] with or without irrigation on disk, sweep, or no‐tillage plots, and continuously on dryland and irrigated plots with sweep and disk tillage, respectively. Dryland wheat with sweep tillage yielded 2,250 kg/ha where the irrigated and dryland crops were alternated and 2,080 kg/ha on continuous dryland plots, a significant yield increase. For irrigated wheat with disk tillage, yields were similar where irrigated and dryland crops were alternated or where continuously irrigated.For the tillage evaluations, dryland wheat yields with sweep and disk tillage were similar, averaging 2,250 and 2,330 kg/ha, respectively. Yields for both were significantly higher than the 2,120‐kg/ha no‐tillage average. Irrigated wheat yielded 4,650 with sweep, 4,390 with disk, and 4,220 kg/ha with no‐tillage in the tillage evaluation. The differences were significant. By comparisons, dryland wheat yielded significantly more grain with sweep or disk tillage in the irrigated and dryland system than in the continuous dryland system (with sweep tillage). With irrigation, wheat yielded significantly more with sweep tillage in the alternate system than with disk tillage in the continuous and alternate systems.Considering the combined system and tillage effects, the best treatments were sweep tillage for irrigated wheat and disk or sweep tillage for dryland wheat. Using sweep and disk tillage for irrigated and dryland wheat, respectively, where the crops are alternated increased average grain yields 10.3% over the average for the continuous irrigated and continuous dryland treatments. The greater grain yield occurred with 8.4% more soil water use, but only 2.3% more total water use. Wateruse efficiency was 8.5% greater where irrigated and dryland crops were alternated than where irrigated and dry]and crops were grown continuously. The irrigated and dryland alternate system offers a potential for greater and more water‐efficient grain production than that possible where equal areas are continuously cropped to irrigated or dryland wheat.

Competitive interaction of grasses with contrasting temperature responses and water stress tolerances

Lolium perenne (cv. Kangaroo Valley ryegrass), L. perenne x multiforum (cv. 'Grasslands Manawa' short rotation ryegrass), Phalaris tuberosa (cv. Australian Commercial),Festuca arundinacea (cv. Demeter) and Paspalum dilatatum were grown for 2 years in monoculture and two-species mixtures, under dryland and irrigated treatments at Armidale, N.S.W. Competition effects were described, with the use of diallel analysis. Early aggressivities were in the order L. perenne × multiflorum > L. perenne > F. arundinacea = P. tuberosa > P. dilatatum in both water treatments; subsequently, the aggressiveness of F. arundinacea, P. tuberosa and P. dilatatum increased relative to the ryegrasses (especially L. perenne), P. tuberosa (more so in the dryland treatment) and P. dilatatum (particularly in summer and autumn). Specifically high aggressivities of P. tuberosa towards P. dilatatum and P. dilatatum towards L. perenne were shown. Under dryland conditions, the P. tuberosa monoculture produced the highest yield in both years, differing markedly from L. perenne × multiforum in response to limited water availability. Under irrigation overall gains of yield were obtained by mixing grasses in the second year, the gains being significant for ryegrass-P. dilatatum mixtures. This response is related to the different growth potentials of the species in different seasons with the proviso that conditions such as water stress or excess suppression do not limit the expression of these potentials. Although P. dilatatum was of lower digestibility than the ryegrass, the difference was not sufficiently large to cancel the gain from mixing when expressed as digestible organic matter (DOM). An unsatisfactory feature of these mixtures was the depressive effect on winter yield of dormant P. dilatatum. By comparison, winter yield stimulation by mixing P. tuberosa and L. perenne, occurring when digestibilities were high, contributed to a significant gain of DOM yield by this mixture. Marked dominance of L. perenne × multiforum under dryland conditions, although appearing to assist the survival of this species in mixture, was detrimental in that by suppressing P. tuberosa, F. arundinacea and P. dilatatum, it restricted the potential of these species to produce in dryland conditions. There was evidence that F. arundinacea depressed yield in mixture, especially when associated with L. perenne.