Influence of corn hybrids and water stress on yield and nutritive value

Silage corn (Zea mays) in Texas has increased from 16,000 ha harvested in 1985 to 53,000 ha harvested in 2005. All corn in the Texas High Plains is irrigated with water from the Ogallala Aquifer. Due to the declining water level of the Ogallala Aquifer and rising energy costs, corn silage producers need new hybrids that require less water and respond to improved crop management practices. As the dairy industry continues to grow in West Texas, producers must supply a high-quality, high-yielding corn forage that meets the nutritional demands of the dairy industry.

The objective of this study was to compare the responses in regards to grain yield, forage yield and quality of five Texas Agricultural Experiment Station (TAES) corn hybrids and three widely grown commercial hybrids (Garst 8288, P31B13, and DKC66-80) under full and limited irrigation treatments. This experiment was conducted in 2005 and 2006, at Halfway, TX and Etter, TX. There were two irrigation treatments (well-watered and drought-stressed) at Etter and Halfway in both years. Drought stress was imposed by reducing the amount of irrigation water by one-half compared to well-watered plots from V10 to R3 growth stages.

Plots were two-rows 5.5 m long and spaced 1 m apart at Halfway and 0.76 m apart at Etter. After planting, plots were thinned to 66,947 plants/ha at Etter and 57,383 plants/ha in Halfway. Data was collected on grain yield, silage yield, plant height, ear height, days to pollen, neutral detergent fiber (NDF), acid detergent fiber (ADF), crude protein and numerous other forage quality traits. Whole plant corn samples were collected and sub-samples were analyzed by Dairy One Forage Laboratory (Ithaca, NY) using Near Infrared Reflectance Spectroscopy (NIRS). The basic experimental design for this analysis was a randomized complete block design with two blocks (locations); irrigation treatments (100ET and 50ET) represented the main plot factor of a split-plot arrangement, and hybrid was a subplot factor.

No three-way interactions were observed among year, irrigation, and hybrid for any of the variables analyzed. Additionally, interactions between irrigation and hybrid, and between irrigation and year, were not present for any of the variables analyzed. Effects of hybrids depended on the year of the experiment (year X hybrid interaction) for percentage ADF, NDF, TDN, and DM. For grain yield, per plant fresh weight (FW plant-1), DTP, PHT and EHT, differences among hybrids were independent of other factors included in this study. Thus, differences among hybrids were averaged over each yr and effects of hybrid and irrigation treatment were examined.
Differences among hybrids were observed for grain yield (kg ha-1), FW plant-1, DTP, PHT, and EHT. When analyzing grain yield, the commercial check P31B13 (8703 kg ha-1) was the highest yielding hybrid with the exception of C3A654 x B110 (7800 kg ha-1) and DKC66-80 (8044 kg ha-1). In terms of FW plant-1, S1W x CML343 yielded a greater fresh weight per plant than any other hybrids except DKC66-80, while C3A654 x B110 yielded the least fresh weight per plant. Also, S1W x CML343 was the latest maturing hybrid when compared to all others and took an average of 80 d to anthesis (DTP). In terms of plant height, S2B73 x NC300 was a taller hybrid than Tx205 x B110 (230.6) and C3A654 x B110 (210.3) as it averaged 244.4 cm, while, C3A654 x B110 was statistically the shortest when compared to all other hybrids as it measured just over 210 cm on average.
Drought stress (50% ET irrigation) did affect both ADF and NDF in terms of forage quality. Both cell wall (NDF) and cell wall minus hemicelluloses (ADF) were higher in hybrids subjected to water stress than hybrids irrigated at 100% ET. Irrigation level did not affect percentage CP and TDN. Grain yield was reduced about 50% by the low irrigation treatment compared with full irrigation. Surprisingly, there were no statistical differences found in the forage yield (FW plant-1) or in DTP with the imposition of drought.

Effects of year and hybrid interacted with each other for ADF, NDF, TDN and DM. For DM, hybrids were similar (P > 0.1560) in 2005 and differed (P < 0.0001) in 2006. However, for ADF, NDF and TDN, hybrids differed in each year.

In future studies the integration of brown mid-rib hybrids should be made a priority. Some hybrids from this study did show promise and should be considered for future studies as well. Although S1W x CML343 lacked the quality traits that some of the other hybrids, it should not be ruled out on that premise alone. It did appear to be one of the higher yielding hybrids and should be considered for future studies. While C3A654 x B110 did appear to produce higher quality forage, it also had the shortest plants and might lack the overall forage production when being considered for future studies. Also, SPG3 x B110 appeared to have quality traits that would be very desirable and at the same time may include some higher yielding traits and should be used in potential studies.

A major limitation in this study was the inclusion of only two blocks, although the two locations did serve as valid blocks. More research and detailed analysis must be performed in order to select for high yielding, high producing corn forage that might potentially use less water. This study may help to serve as a reference to future researches.