Low lignin alfalfa cutting management study

Abstract

Alfalfa (Medicago sativa L.) is the fourth most valuable cash crop in the U.S., following corn, wheat, and soybean, and its production is vital to sustain the dairy, beef, and hay industries. As the world population increases alongside environmental degradation and water scarcities, identifying monthly climate variables related to alfalfa production can provide growers and researchers more time to deal with the effects of climate change. The purpose of Chapter 1 was to propose a statistical learning method to investigate, access, and predict the relationship between the alfalfa yield and monthly climate information with much larger numbers of variables in the state scale. To address the high-dimensionality of monthly climate variables, we employed a penalized regression model, called Lasso. Less than six relevant climate variables (i.e. monthly maximum and minimum temperature, and monthly precipitation) were identified as important predictors for alfalfa yields in each state. It was also shown that at least one of climate variables in June, July, and August was highly correlated to alfalfa yields. Reduction of lignin level in the forage legume alfalfa by the conventional breeding technology results in increased digestibility and may extend peak harvest dates by up to 10 days. This could benefit alfalfa growers by avoiding undesirable weather conditions, such as heavy rain, and increasing dry matter yield and nutritive values. The objective of Chapter 2 was to evaluate field performance and cash value of low lignin and reference variety under a four-cut system. The experiment was a split-plot design with a randomized complete block, the whole plot factor with two levels of variety and the subplot factor with six levels of harvest schedule. Forage yield differences among harvest schedules were more pronounced than yield differences between two varieties. Harvest interval had a significant effect on the nutritive value of alfalfa and a more substantial effect than variety selection. The nutritive value of low lignin alfalfa variety was significantly greater than the conventional variety. The purpose of Chapter 3 was to compare forage yield and nutritive value of low lignin alfalfa and two reference varieties subjecting to two harvest intervals and three seeding rates. The experimental design was in a split-split plot arrangement with four replicates, where harvest intervals (28-day and 35-day) were assigned to whole plots, seeding rates were subplots, and varieties were sub-subplots. The weighted mean nutritive value was applied to two production years of 2016 and 2017. Hi-Gest 360 (low lignin alfalfa) provided similar yield potential and increased nutritive value compared to two reference varieties. Harvest interval had a large effect on nutritive value and a more significant effect on alfalfa dry matter yield than variety selection. Seeding rate did not affect alfalfa yield and nutritive value. Based on two production year research in Manhattan, KS, the low lignin alfalfa variety under a shorter harvesting interval (every 28-day) appears be profitable management practice regardless of seeding rate.