Growing Degree Units Research Articles

Harvest Date and Hybrid Influence on Corn Forage Yield, Quality, and Preservation

The selection of corn (Zea mays L.) hybrids and the timing of harvest are important management considerations for dairy and livestock operations. Objectives of this study were to determine the effect of harvest date on yield and quality of corn hybrids and to describe the relationship between harvest date and the yield and quality of corn forage, silage, and stover. During 1998 and 1999, four hybrids were harvested at eight different harvest times between 521 and 1224 growing degree units (GDUs) after planting. Few hybrid or hybrid × harvest date effects were observed. As GDUs accumulated, dry matter yield increased from 8 to 25 Mg ha−1. Lowest concentrations of neutral detergent fiber (NDF) and acid detergent fiber (ADF) and highest concentrations of in vitro true digestibility (IVTD) occurred when forage was harvested between 700 and 650 g kg−1 moisture (1025 and 1186 GDUs after planting). Potential milk yield indices of milk Mg−1 corn forage (794 kg) and milk ha−1 corn forage (19 049 Mg) were reached when corn was harvested between 670 and 630 g kg−1 moisture. In general, silage had 15% lower concentrations of NDF, 8% lower IVTD, 48% lower cell wall digestibility, 7% lower crude protein, and 15% higher concentrations of ADF than unfermented fresh forage. Harvesting can be accomplished until 580 g kg−1 moisture while maintaining 95% of the maximum yield and milk ha−1

Harvest Date and Hybrid Influence on Corn Forage Yield, Quality, and Preservation

The selection of corn (Zea mays L.) hybrids and the timing of harvest are important management considerations for dairy and livestock operations. Objectives of this study were to determine the effect of harvest date on yield and quality of corn hybrids and to describe the relationship between harvest date and the yield and quality of corn forage, silage, and stover. During 1998 and 1999, four hybrids were harvested at eight different harvest times between 521 and 1224 growing degree units (GDUs) after planting. Few hybrid or hybrid × harvest date effects were observed. As GDUs accumulated, dry matter yield increased from 8 to 25 Mg ha−1. Lowest concentrations of neutral detergent fiber (NDF) and acid detergent fiber (ADF) and highest concentrations of in vitro true digestibility (IVTD) occurred when forage was harvested between 700 and 650 g kg−1 moisture (1025 and 1186 GDUs after planting). Potential milk yield indices of milk Mg−1 corn forage (794 kg) and milk ha−1 corn forage (19 049 Mg) were reached when corn was harvested between 670 and 630 g kg−1 moisture. In general, silage had 15% lower concentrations of NDF, 8% lower IVTD, 48% lower cell wall digestibility, 7% lower crude protein, and 15% higher concentrations of ADF than unfermented fresh forage. Harvesting can be accomplished until 580 g kg−1 moisture while maintaining 95% of the maximum yield and milk ha−1

Spatial and temporal expansion patterns ofApocynum cannabinumpatches

Abstract There is little information published on patch expansion of perennial weeds and none for Apocynum cannabinum. Studies were conducted to measure the between-season and in-season expansion patterns of natural A. cannabinum patches over three growing seasons. Regression analysis indicated strong relations between patch area in consecutive years 1996 to 1997 (r2 = 0.81) and 1997 to 1998 (r2 = 0.76). Patches less than 20 m2 in 1996 increased in area by more than 100% in 1997 during a fallow season. However, patches decreased in size 6 to 51% between 1997 and 1998 when Glycine max was grown. Evidence suggested that a late-season mowing of the A. cannabinum patches in 1997 contributed more to the decline in patch area than competition from G. max during the 1998 season. The relations between patch area and growing degree units (r2 = 0.97) indicated that greater than 89% of the terminal patch expansion occurred prior to the accumulation of 435 growing degree units (GDU) (June 19, 1997; May 31, 1998; June...

An explanation of genotype by environment interaction for maize in South Africa

The causes of genotype interaction with the environment was investigated using AMMI (Additive Main Effects and Multiplicative Interaction) analysis. AMMI quantified environments by means of E_IPCA1 (first principal component analysis for environment) such that it was highly significantly correlated (r = -0.79) with accumulated growing degree units (GDUs) during the growing season. G_IPCA1 (first principal component analysis for genotype) scores were highly significantly correlated with growth rate related observations, such as days to 50% pollen shed (-0.77), days to physiological maturity (-0.81), and grain moisture at harvest (-0.87). Multiple linear regression analysis of data led to the conclusion that GJPCA1 scores can be explained with R2 = 0.80 accuracy from a combination of grain moisture at harvest and either days to physiological maturity, or days to pollen shed. The AMMI required that E_IPCA1 and G_IPCA1 scores should, both be either positive or negative in order to increase AMMI1 yield estimates. This means that hybrids with a slower growth rate will be better adapted to environments with more GDUs during the growing season, and hybrids with a faster growth rate will be better adapted to environments with less GDUs during the growing season. This conclusion suggests that temperature, especially minimum night temperature, which determines the rate of development between physiological stages in the maize plant, may be a major contributor to genotype by environment interaction.

Apocynum cannabinumseed germination and vegetative shoot emergence

Apocynum cannabinumis a native creeping perennial distributed throughout the U.S., with increasing importance in reduced tillage systems throughout the Midwest.Apocynum cannabinumhas been shown to be a difficult species to control in field crops. Effective weed management is often a function of the timing of control practice. Knowledge of weed emergence patterns may be useful in predicting the optimum time of weed management. The objectives of these studies were to describe how temperature and moisture affectA. cannabinumseed germination and to describe the relationship between growing degree units (GDU) andA. cannabinumvegetative shoot emergence. At constant temperatures, seed germination was described as a sigmoidal function of temperature (r2= 0.83), with maximum germination (32%) from 26 to 34 C. Under alternating temperatures, seed germination increased in a linear relationship between mean temperatures of 15 and 34 C (r2= 0.85). Maximum seed germination (88%) occurred at a mean temperature of 34 C under alternating temperatures. The relationship between seed germination and osmotic potential between −1.0 and 0 MPa was described by a gompertz function (r2= 0.98). Germination at −1.0 MPa was 4% and increased in a near linear manner to the nontreated control (0 MPa), which had 80% germination. Vegetative shoot emergence in 1997 and 1998 had a sigmoidal relationship to GDU using a base temperature of 6 C (r2= 0.96). However, initial shoot appearance was not consistent over years, with first emergence recorded on May 21, 1997 (132 GDU), and May 5, 1998 (73 GDU). Approximately 50% of the shoots emerged before June 7, 1997 (282 GDU), and May 21, 1998 (285 GDU); therefore, optimal weed management programs will need to be initiated following this GDU accumulation.

Aerial accumulation and partitioning of nutrients by hard red spring wheat

Abstract Periods of maximum hard red spring (HRS) wheat (Jriticum aestivum L.) nutrient demand need to be determined in order to develop best nutrient management practices, and to provide data for nutrient uptake modeling. Aerial (aboveground biomass) whole plant samples of irrigated HRS wheat were collected from the field at 16 growth stages and separated into leaves, stems, heads, and grain for dry matter determinations and analyzed for N, P, K, Ca, Mg, S, Cl, Zn, Mn, Fe, and Cu concentrations. Accumulation curves were computed for each plant part for the growing season from compound cubic polynomial models based on accumulated growing degree units (GDUs). Total aerial accumulations of dry matter, N, P, K, Ca, Mg, S, Cl, Zn, Mn, Fe, and Cu were 14400, 116, 30.8, 103, 9.2, 9.3, 15.2, 32.3, 0.18, 0.58, 2.05, and 0.045 kg/ha, respectively. Grain at maturity accumulated greater than 78% of the total aerial N, P, and Zn, while it contained less than 20% of the aerial accumulated K, Ca, Cl, and Fe. Nitrogen a...

Changes induced by cowpea green manure and farmyard manure in the timing of phenological events in maize (Zea mays)

SUMMARYThe effect of cowpea green manure (CGM) and farmyard manure (FYM) on phenological events in maize grown with different rates of nitrogen (N) was evaluated at Ludhiana, India in 1988–89 as part of a long-term experiment on sandy loam. Tasselling (T), anthesis (A), silking (S), maturity (M) and appearance of leaves were recorded in 1988 and 1989 from plots of maize manured with cowpea and FYM and grown at 0, 75 and 125 kg N/ha. Time to phenological events was calculated in terms of calendar days and growing degree units (GDU).Phenological events in maize were significantly advanced by CGM, FYM and N. The occurrence of T, A and S with CGM was earlier by 60·5, 84·5 and 114·5 GDU, respectively, than without it and the end of each of the growth stages T, A and S was advanced by 81·0, 99·0 and 78·5 GDU, respectively. Maturity was earlier than in the control by 65·0 GDU. Leaf emergence occurred earlier after organic manuring. Farmyard manure advanced development less than CGM. Changes in phenological events due to N followed the same pattern of changes as those found with organic manures. Time from sowing to onset of T, A, S and M, and the interval between T, A, S and M were significantly correlated with yield and yield-related characters. Desirable changes in the timing of phenological events are thus one of the factors contributing to the improvement in productivity caused by organic manures. Calendar day was found to be as accurate an index as GDU for evaluation of the effect of cultural practices on phenological events.

Fertilizer use efficiency

Abstract The combined effects of improved hybrids, better water management, increased nutrient application rates, and higher plant populations have significantly increased maize (Zea mays L.) dry matter, grain yield, and nutrient accumulation when compared to benchmark data collected by Sayre in 1940 and Hanway in 1959. To evaluate the effects of those changes in management practices on seasonal rates of accumulation, aerial dry matter, N, P and K accumulation data from the benchmark studies, 2 recent field studies and a 1985 maximum economic yield (MEY) study were described with compound cubic polynomials. The equations were differentiated to determine rates and plotted as a function of growing degree units. Aerial accumulation patterns were similar for all 5 studies even though grain yields averaged 6.4 and 7.1 Mg ha‐1 in the benchmark studies, 9.7 and 14.0 Mg ha‐1 in recent studies, and 19.3 Mg ha‐1 in the MEY study. Peak daily N, P and K accumulation rates during vegetative growth were 3, 2, and 6 tim...

Potential CO2-induced climate effects on North American wheat-producing regions

The environmental requirements for growth of winter, spring, and fallsown spring wheats in North America are specified and compared to temperature results from the control run of the Goddard Institute for Space Studies general circulation model (GISS GCM) and observed precipitation in order to generate a simulated map of current wheat production regions. The simulation agrees substantially with the actual map of wheat-growing regions in North America. Results from a doubled CO2 run of the climate model are then used to generate wheat regions under the new climatic conditions. In the simulation, areas of production increase in North America, particularly in Canada, due to increased growing degree units (GDU). Although wheat classifications may change, major wheat regions in the United States remain the same under simulated doubled CO2 conditions. The wheat-growing region of Mexico is identified as vulnerable due to high temperature stress. Higher mean temperatures during wheat growth, particularly during the reproductive stages, may increase the need for earlier-maturing, more heat-tolerant cultivars throughout North, America. The soil moisture diagnostic of the climate model is used to analyze potential water availability in the major wheat region of the Southern Great Plains.