Nitrogen utilization efficiency, growth and yield response of maize (zea mays l.) to integrated application of mineral nitrogen and cattle manure

Numerous efforts have been put into maize research in Ghana over the years, however, productivity in farmers’ fields generally remained low, averaging 1.6 tons/ha. This low productivity has been attributed among other factors, to inappropriate nutrient management practices. A study was conducted at the Plantation Crops Section of the Department of Crop and Soil Sciences, Kwame Nkrumah University of Science and Technology, Ghana to identify effective cattle manure and mineral nitrogen (N) combination practices that will improve nitrogen utilization and maize productivity. Three field experiments were carried out in the study. The first was conducted in the 2014 major season, whilst the second and third were respectively conducted in the 2014 minor and 2015 major seasons. All three experiments were conducted within the same area but on different fields. The experiments were factorial in a randomized complete block design with four replications. Obatanpa was used as the test crop. The first two experiments had the same treatments with two factors i.e. cattle manure and time of nitrogen application. Cattle manure comprised four rates: 0, 2, 4 and 6 tons/ha. Nitrogen application times were as follows: 50% N at 2 weeks after planting and 50% at 4 WAP (NT1), 50% N at 2 WAP and 50% at 6 WAP (NT2), 50% N at 2 WAP and 50% at 8 WAP (NT3) and a control (0 kg N/ha). The third experiment comprised two factors i.e. cattle manure rates as in the previous experiments and mineral nitrogen rates as follows: 0, 30, 60 and 90 kg N/ha. Nitrogen uptake by aboveground plant parts was higher when inorganic N was applied in combination with cattle manure than when inorganic N or cattle manure alone was applied. It was also higher in inorganic N treatments than manure treatments. Among the times of N application, N uptake was higher at NT2. Nitrogen uptake increased with increase in N rate, but at a diminishing return. Remobilization of N from vegetative parts to the ears during grain filling was severe from leaves than culms; and in the control than in the mineral nitrogen and manure treatments. It was also relatively smaller at NT2 than at other N application times, and at higher N rates than lower rates. Applications of manure significantly (P < 0.05) reduced N remobilization in the 4 and 6 tons/ha manure treatments. Nitrogen use efficiency was higher at NT2 application time. Among the N rates, NUE was higher at 60 kg than at 30 and 90 kg N rates, but was also significantly higher (P < 0.05) at 30 kg than at 90 kg N rate. Crop growth rate and other growth parameters were mostly higher at NT2 than at other application times; and at higher than lower mineral nitrogen and manure rates. Dry matter accumulation was also greater at NT2 application time and increased with increase in N and manure rates. Leaf dry matter responded more to variations in nitrogen application, which makes leaves better indicators of nitrogen effect on maize dry matter partitioning than culms. Grain yield was higher in inorganic N and manure combined treatments than in sole inorganic N and sole manure treatments. Higher grain yields recorded in the nitrogen and manure combined treatments was as a result of higher N uptake, NUE, dry matter accumulation and growth parameters obtained in these treatments. The 60 kg N combined with 6 tons/ha cattle manure treatment effect on most of the parameters studied was higher than that of the 90 kg sole mineral nitrogen treatment effect and statistically the same as the 90 kg N combined with 6 tons/ha cattle manure treatment. Considering side effects of excessive N application on the environment and on production cost, application of 60 kg N/ha at NT2 in combination with 6 tons/ha cattle manure is a promising technology for greater nitrogen utilization and higher maize grain yield.

Source: KNUST